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Received: 19 December 2024
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Accepted: 20 January 2025
Published: 17 February 2025
Citation: Recio-Colmenares, C.L.;
Flores-Gómez, J.; Morales Rivera, J.P.;
Palacios Hinestroza, H.; Sulbarán-
Rangel, B. Green Materials for
Water and Wastewater Treatment:
Mechanisms and Artificial Intelligence.
Processes 2025,13, 566. https://
doi.org/10.3390/pr13020566
Copyright: © 2025 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license
(https://creativecommons.org/
licenses/by/4.0/).
Review
Green Materials for Water and Wastewater Treatment:
Mechanisms and Artificial Intelligence
Carolina Livier Recio-Colmenares 1, Jean Flores-Gómez 1, Juan Pablo Morales Rivera 1,
Hasbleidy Palacios Hinestroza 2and Belkis Sulbarán-Rangel 1, *
1Department of Water and Energy, Tonala Campus, University of Guadalajara, Tonalá 45425, Mexico;
carolina.recio@academicos.udg.mx (C.L.R.-C.); jean.flores9810@academicos.udg.mx (J.F.-G.);
juan.morales9853@academicos.udg.mx (J.P.M.R.)
2Department of Basic Sciences, Campus Tlajomulco, University of Guadalajara,
Tlajomulco de Zúñiga 45641, Mexico; hasbleidy.palacios@academicos.udg.mx
*Correspondence: belkis.sulbaran@academicos.udg.mx
Abstract: Green materials are emerging as sustainable alternatives in water and wastewater
treatment. Due to their biodegradability, renewable origin and low toxicity characteristics,
green materials are an alternative to conventional synthetic materials. Green materials
include nanomaterials of natural origin, biopolymers and composites that optimize the
adsorption and removal of contaminants. The applications of cellulose nanofibers, alginates,
chitosan and lignin stand out, as well as functionalized hydrogels and aerogels for the
removal of heavy metals, dyes and organic contaminants. The analysis of the mechanisms
and processes of contaminant removal and modeling and optimization techniques are
included as key emerging tools for the design and optimization of these materials, allowing
one to predict properties, simulate interactions and customize solutions. Despite the
sustainability benefits of green materials, they face technical and economic challenges, such
as scalability, synthesis costs and experimental validation. This work concluded that green
materials, combined with modeling and optimization tools, are essential to move towards
more sustainable, efficient and environmentally friendly water treatment technologies,
aligned with global objectives of sustainable development and climate change mitigation.
Keywords: green material; mechanisms; natural polymers; modeling tools
1. Introduction
As the global population continues to grow, water and wastewater treatment has
become essential to address the severe pollution of receiving reservoirs and the scarcity
of drinking water [
1
]. Within the framework of the 2030 Agenda on Sustainable Develop-
ment, of the 17 proposed Development Goals, Goal 6, which consists of guaranteeing the
availability of water and its sustainable management and sanitation for all, aims for water
to remain free of impurities in addition to being accessible to all human beings since it is an
indispensable natural resource in the environment in which life develops [
2
]. In order to
comply with water and wastewater sanitation, there are different technological treatments
that seek that water has adequate quality for both consumption and for discharge into
receiving water bodies [
3
]. Water and wastewater treatments are a set of unit operations of
a physical, chemical or biological nature whose purpose is to eliminate or reduce contami-
nation or undesirable characteristics of water [
4
]. These treatments are designed based on
the contaminants present in the effluents, which may contain one or more contaminants
such as suspended solids, heavy metals, oils and fats, recalcitrant organic compounds, toxic
Processes 2025,13, 566 https://doi.org/10.3390/pr13020566
Processes 2025,13, 566 2 of 29
compounds, emerging contaminants (antibiotics, hormones and microplastics), among
others [5].
In several water and wastewater treatment systems, materials are used; these can be
organic or inorganic and play a key role in these treatments by offering efficient solutions to
remove contaminants and disinfect and reuse the resource [
4
,
6
]. Inorganic materials, such
as ceramic membranes, zeolites and metal oxides (e.g., TiO
2
), are notable for their chemical
and thermal stability, making them ideal for demanding processes such as advanced
filtration and photocatalysis [
7
–
9
]. Metals and alloys, such as zero-valent iron and silver
or copper nanoparticles, are used in advanced oxidation and pathogen removal [
6
,
10
].
On the other hand, polymeric synthetic materials, such as polyamide membranes and
ion exchange resins, offer versatility and adaptability, being essential in processes such as
reverse osmosis and demineralization [
11
,
12
]. Their application ranges from the treatment
of industrial wastewater to the improvement of the quality of drinking water in homes.
However, after carrying out these treatments, waste is generated with the contaminants
removed from the wastewater [
13
]. One proposal that is being considered is to find a
way to take advantage of the waste obtained after the physical–chemical treatments of
wastewater through the circular economy [
14
,
15
] or to use materials with recyclability
or biodegradability characteristics that are incorporated into the environment without
generating pollution, the so-called green materials [7,16].
At present, one of the most widely used green materials in water treatment systems is
activated carbon, which is obtained from lignocellulosic biomass [
17
,
18
]. However, there
are other green materials that are being researched that have not yet reached the level of
performance and durability to compete with conventional materials; therefore, the need for
continuous research and development to improve upon them arises. This technical and
scientific challenge is especially critical in industrial applications, where materials are re-
quired to withstand extreme conditions and maintain constant performance over time [
19
].
In the face of escalating environmental challenges, green materials have emerged as pivotal
in mitigating the ecological footprint of industrial and consumer activities [
20
]. These
materials, characterized by their renewable origins and minimized environmental impact
throughout their lifecycle, represent a paradigm shift in sustainable practices. However,
their effective integration into real-world applications necessitates a comprehensive under-
standing of their properties, limitations and potential contributions to global sustainability
frameworks [21].
Green materials are primarily defined by their renewable origins, a feature that signifi-
cantly reduces dependency on fossil resources. For instance, bioplastics such as polylactic
acid (PLA) and starch-based polymers emit up to 75% fewer greenhouse gases during
their production compared to conventional plastics [
22
,
23
]. Yet, this benefit is not without
trade-offs. The high water and energy requirements of bioplastic production raise concerns,
particularly in water-stressed regions. Additionally, the utilization of agricultural crops
as feedstocks introduces a conflict with food security, prompting the need for alternative
sources such as lignocellulosic biomass or agro-industrial residues. However, despite these
limitations, the demand for green materials continues to grow, driven by a cultural and
economic shift towards sustainability. Both consumers and industries are prioritizing solu-
tions that reduce their environmental impact and contribute to climate change mitigation.
This change in market preferences is encouraging manufacturers to invest in innovation
to develop materials that are more affordable, high-performing, and environmentally
friendly [
22
]. Therefore, the aim of this research is to review the current status of green
materials applied in water and wastewater treatment as these materials are presented as a
key tool to address the global challenges associated with climate change and the depletion
of natural resources. Specifically, the objective of our research is to show the basic concepts
Processes 2025,13, 566 3 of 29
of green materials, the most common classifications and the mechanisms of action with
respect to water and wastewater treatment systems. In addition, nanomaterials of natural
origin or produced by green synthesis will be integrated as they represent innovations with
a high capacity to adsorb emerging pollutants and heavy metals at the nanometric scale.
This research will also integrate the use of modeling and optimization techniques in the
design and optimization of these materials since, with these tools, it is possible to predict
properties, simulate interactions and customize solutions according to the characteristics of
the treated water. Overall, the diversity and unique properties of green materials, combined
with modeling and optimization techniques, will boost sustainability and efficiency, being
essential to face the current and future challenges in water management.
2. Definition and Criteria of Green Materials
Green materials are defined as those designed to minimize environmental impact
throughout their entire life cycle. These materials, often derived from renewable sources
such as plants or recycled materials, are developed with the purpose of conserving re-
sources, reducing waste and minimizing pollution [
23
]. Among their primary character-
istics is their renewable origin, which contributes to reducing the dependence on non-
renewable resources such as fossil fuels [
24
]. For instance, bioplastics such as polylactic
acid (PLA) and starch-based polymers emit up to 75% fewer greenhouse gases during their
production compared to conventional plastics [
25
,
26
]. Similarly, the production processes
associated with these materials prioritize efficiency, decreasing energy consumption, water
usage and greenhouse gas emissions, aligning with sustainability principles [
26
]. Likewise,
their non-toxic or low-toxicity nature ensures the safety of both humans and the environ-
ment, promoting their acceptance in a wide range of applications [
27
]. Furthermore, green
materials often play a crucial role in improving energy efficiency, whether in buildings
or products, reducing operational costs or mitigating associated carbon footprints [
28
].
Another relevant aspect is their capacity for recycling or biodegradation at the end of their
useful life. For instance, poly(butylene succinate) (PBS) demonstrates complete degra-
dation within six months under industrial composting conditions, yet its breakdown is
significantly slower in natural environments due to suboptimal microbial activity and
environmental conditions [
20
]. This discrepancy highlights the importance of establishing
infrastructure tailored to optimize the biodegradability of such materials. Furthermore,
without robust end-of-life management systems, biodegradable materials risk contribut-
ing to landfill accumulation, thereby undermining their sustainability objectives. The
biodegradability and recyclability facilitate the integration of these materials into circular
economy models, helping to manage resources sustainably and significantly reduce waste
generation [29].
Green materials find applications in various sectors, reflecting their versatility and
ability to minimize environmental impact. In the construction sector, the use of sustainable
materials such as bamboo, recycled wood and low volatile organic compound (VOC) paints
has proven to be an effective strategy for reducing the environmental footprint of building
projects [
30
]. Biodegradable materials, such as plant-based polymers and recycled paper,
are a sustainable alternative in packaging, helping to reduce plastic waste. In the textile
industry, the use of eco-friendly fabrics such as organic cotton and recycled polyester
decreases environmental impact by reducing chemicals and water consumption [
20
]. In
electronics, eco-friendly devices employ recycled materials and recyclable designs to min-
imize electronic waste [
31
]. In transportation, biofuels and recyclable materials improve
efficiency and reduce emissions [
32
]. Consider that criteria such as biodegradability, low
toxicity, the utilization of renewable resources and life cycle assessment are fundamental in
the development and application of advanced green materials for water and wastewater
Processes 2025,13, 566 4 of 29
treatment. These criteria not only guarantee the long-term sustainability of treatment
processes but also protect public health and minimize the environmental impact of water
purification technologies [
33
]. Conventional materials, such as activated carbon, alum and
chlorine, have been widely used in water treatment for decades [
34
]. These materials have
proven effective in removing traditional contaminants such as organic matter, heavy metals
and microorganisms [
35
]. However, their use is not without significant environmental im-
pacts, such as the emission of greenhouse gases and the generation of hazardous waste [
36
].
Additionally, their effectiveness may be limited in the removal of emerging contaminants
or in the removal of low concentrations of certain compounds [
37
]. In contrast, green
materials offer a more sustainable approach to water treatment. Frequently derived from
renewable sources, such as agricultural waste or natural minerals, these materials exhibit
production processes with a lower environmental impact [
38
]. A distinctive advantage of
green materials is their ability to be specifically designed to treat specific contaminants,
making them highly versatile in water treatment applications. Furthermore, many of these
materials are biodegradable, significantly reducing the risk of long-term environmental
damage [
39
]. For example, cellulose nanofibers derived from lignocellulosic biomass ex-
hibit specific surface areas exceeding 300 m
2
/g, making them highly effective in adsorbing
heavy metals and organic pollutants [
40
,
41
]. Integrated into polymeric membranes, these
materials enhance filtration efficiency and mechanical stability, achieving removal rates of
up to 95% in wastewater treatment systems [41].
Composite materials represent a complementary category, combining renewable com-
ponents with synthetic matrices to enhance mechanical strength, thermal stability and
adsorption capacity. Biopolymer–clay composites, for instance, merge the high adsorp-
tion capacity of clays like montmorillonite with the functional versatility of biopolymers
such as chitosan, enabling the effective removal of heavy metals and dyes under diverse
environmental conditions [
42
]. Similarly, the incorporation of zinc oxide nanoparticles into
biopolymer matrices has significantly improved the photocatalytic degradation of organic
pollutants, achieving reductions exceeding 80% under UV irradiation [
43
]. While this con-
ventional classification offers a foundational framework, it does not fully encapsulate the
diversity and multifunctionality of advanced green materials. Expanding the framework
to include additional criteria, such as origin, key properties and primary applications,
provides a more nuanced understanding. Materials can be categorized based on their
origin as bio-based, recycled or natural. Properties such as energy efficiency, environmental
impact and durability further distinguish these materials, highlighting their suitability for
specific applications. For instance, bio-based materials like cellulose and chitosan offer
renewable alternatives for water filtration and heavy metal adsorption, while recycled
materials contribute to resource circularity by repurposing industrial or consumer waste.
3. Classification of Advanced Green Materials
Advanced green materials are essential for addressing urgent environmental chal-
lenges, particularly in water treatment and contaminant remediation. Understanding
their classification allows for a more precise characterization of their properties and uses,
maximizing their potential in specific applications. Following the categorization by Ku-
mar [
31
], advanced green materials can be broadly classified into two main categories:
green nanomaterials and composite materials.
3.1. Green Nanomaterials
Green nanomaterials are derived from renewable natural resources such as cellulose,
chitosan, lignin, alginate and pectin. Their nanoscale design endows them with unique
properties, including a high surface-to-volume ratio, intrinsic biodegradability and versatile
Processes 2025,13, 566 5 of 29
chemical functionalization [
38
]. These properties make them highly effective in water treat-
ment and contaminant removal. Table 1presents a comparison of various green materials
from renewable natural resources, their origins, chemical structures, and application.
Table 1. Green nanomaterials from renewable natural resources of more common green materials.
Green Materials Origin Structure/Surface-Area Applications References
Cellulose nanofibers
Processes 2025, 13, x FOR PEER REVIEW 5 of 30
3.1. Green Nanomaterials
Green nanomaterials are derived from renewable nat ural resources such as cellulose, chi-
tosan, lignin, alginate and pectin. Their nanoscale design endows them with unique proper-
ties, including a high surface-to-volume ratio, intrinsic biodegradability and versatile chemical
functionalization [38]. These properties make them highly effective in water treatment and
contaminant removal. Table 1 presents a comparison of various green materials from renew-
able natural resources, their origins, chemical structures, and application.
Table 1. Green nanomaterials from renewable natural resources of more common green materials.
Green Materials Origin Structure
/
Surface-Area Applications Reference
Cellulose nanofibers
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Bacteria
Nanoscale, fibrillar structure with
high surface area >300 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[40,41]
Lignin
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Grasses
Three-dimensional aromatic
structure with active functional
groups. Surface area 50–150 m
2
/g.
Adsorption of organic
pollutants, precursor in
carbon materials and re-
inforcement in polymers.
[44]
Chitosan
• Crustaceans
• Fungi
• Insects
• Some invertebrates
Linear structure, glucosamine
polymer with free amino groups.
Surface area 150–200 m
2
/g.
Heavy metal adsorption,
flocculant in water treat-
ment and encapsulation
of bioactive agents.
[45]
Alginate
Algae Linear structure, anionic poly-
saccharide formed by blocks of
guluronic and mannuronic
acid. Surface area 10–50 m
2
/g.
Controlled release sys-
tems, encapsulation and
gel formation in water
treatment. [46]
Formation of biodegrada-
ble films, thickeners in
food and natural adhe-
sives.
Starch
Vegetable plants:
• Tubers
• Seeds of all plants
Granular structure composed
of amylose and amylopectin <
10 m
2
/g.
Emulsion stabilization,
encapsulation of bioac-
tive compounds and
films for sustainable
packaging.
[47]
Pectin
Fruits and vegetables
Branched structure
with galacturonic acid units.
Surface area <10 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[48]
Biomass lignocelluloses:
•Trees and shrubs
•
Agricultural and forestry waste
•Vegetable plants
•Bacteria
Nanoscale, fibrillar
structure with high
surface area >300 m2/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[40,41]
Lignin
Processes 2025, 13, x FOR PEER REVIEW 5 of 30
3.1. Green Nanomaterials
Green nanomaterials are derived from renewable nat ural resources such as cellulose, chi-
tosan, lignin, alginate and pectin. Their nanoscale design endows them with unique proper-
ties, including a high surface-to-volume ratio, intrinsic biodegradability and versatile chemical
functionalization [38]. These properties make them highly effective in water treatment and
contaminant removal. Table 1 presents a comparison of various green materials from renew-
able natural resources, their origins, chemical structures, and application.
Table 1. Green nanomaterials from renewable natural resources of more common green materials.
Green Materials Origin Structure
/
Surface-Area Applications Reference
Cellulose nanofibers
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Bacteria
Nanoscale, fibrillar structure with
high surface area >300 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[40,41]
Lignin
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Grasses
Three-dimensional aromatic
structure with active functional
groups. Surface area 50–150 m
2
/g.
Adsorption of organic
pollutants, precursor in
carbon materials and re-
inforcement in polymers.
[44]
Chitosan
• Crustaceans
• Fungi
• Insects
• Some invertebrates
Linear structure, glucosamine
polymer with free amino groups.
Surface area 150–200 m
2
/g.
Heavy metal adsorption,
flocculant in water treat-
ment and encapsulation
of bioactive agents.
[45]
Alginate
Algae Linear structure, anionic poly-
saccharide formed by blocks of
guluronic and mannuronic
acid. Surface area 10–50 m
2
/g.
Controlled release sys-
tems, encapsulation and
gel formation in water
treatment. [46]
Formation of biodegrada-
ble films, thickeners in
food and natural adhe-
sives.
Starch
Vegetable plants:
• Tubers
• Seeds of all plants
Granular structure composed
of amylose and amylopectin <
10 m
2
/g.
Emulsion stabilization,
encapsulation of bioac-
tive compounds and
films for sustainable
packaging.
[47]
Pectin
Fruits and vegetables
Branched structure
with galacturonic acid units.
Surface area <10 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[48]
Biomass lignocelluloses:
•Trees and shrubs
•
Agricultural and forestry waste
•Vegetable plants
•Grasses
Three-dimensional
aromatic structure with
active functional groups.
Surface area
50–150 m2/g.
Adsorption of organic
pollutants, precursor in
carbon materials
and reinforcement
in polymers.
[44]
Chitosan
Processes 2025, 13, x FOR PEER REVIEW 5 of 30
3.1. Green Nanomaterials
Green nanomaterials are derived from renewable nat ural resources such as cellulose, chi-
tosan, lignin, alginate and pectin. Their nanoscale design endows them with unique proper-
ties, including a high surface-to-volume ratio, intrinsic biodegradability and versatile chemical
functionalization [38]. These properties make them highly effective in water treatment and
contaminant removal. Table 1 presents a comparison of various green materials from renew-
able natural resources, their origins, chemical structures, and application.
Table 1. Green nanomaterials from renewable natural resources of more common green materials.
Green Materials Origin Structure
/
Surface-Area Applications Reference
Cellulose nanofibers
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Bacteria
Nanoscale, fibrillar structure with
high surface area >300 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[40,41]
Lignin
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Grasses
Three-dimensional aromatic
structure with active functional
groups. Surface area 50–150 m
2
/g.
Adsorption of organic
pollutants, precursor in
carbon materials and re-
inforcement in polymers.
[44]
Chitosan
• Crustaceans
• Fungi
• Insects
• Some invertebrates
Linear structure, glucosamine
polymer with free amino groups.
Surface area 150–200 m
2
/g.
Heavy metal adsorption,
flocculant in water treat-
ment and encapsulation
of bioactive agents.
[45]
Alginate
Algae Linear structure, anionic poly-
saccharide formed by blocks of
guluronic and mannuronic
acid. Surface area 10–50 m
2
/g.
Controlled release sys-
tems, encapsulation and
gel formation in water
treatment. [46]
Formation of biodegrada-
ble films, thickeners in
food and natural adhe-
sives.
Starch
Vegetable plants:
• Tubers
• Seeds of all plants
Granular structure composed
of amylose and amylopectin <
10 m
2
/g.
Emulsion stabilization,
encapsulation of bioac-
tive compounds and
films for sustainable
packaging.
[47]
Pectin
Fruits and vegetables
Branched structure
with galacturonic acid units.
Surface area <10 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[48]
•Crustaceans
•Fungi
•Insects
•Some invertebrates
Linear structure,
glucosamine polymer
with free amino groups.
Surface area
150–200 m2/g.
Heavy metal adsorption,
flocculant in water
treatment and
encapsulation of
bioactive agents.
[45]
Alginate
Processes 2025, 13, x FOR PEER REVIEW 5 of 30
3.1. Green Nanomaterials
Green nanomaterials are derived from renewable nat ural resources such as cellulose, chi-
tosan, lignin, alginate and pectin. Their nanoscale design endows them with unique proper-
ties, including a high surface-to-volume ratio, intrinsic biodegradability and versatile chemical
functionalization [38]. These properties make them highly effective in water treatment and
contaminant removal. Table 1 presents a comparison of various green materials from renew-
able natural resources, their origins, chemical structures, and application.
Table 1. Green nanomaterials from renewable natural resources of more common green materials.
Green Materials Origin Structure
/
Surface-Area Applications Reference
Cellulose nanofibers
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Bacteria
Nanoscale, fibrillar structure with
high surface area >300 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[40,41]
Lignin
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Grasses
Three-dimensional aromatic
structure with active functional
groups. Surface area 50–150 m
2
/g.
Adsorption of organic
pollutants, precursor in
carbon materials and re-
inforcement in polymers.
[44]
Chitosan
• Crustaceans
• Fungi
• Insects
• Some invertebrates
Linear structure, glucosamine
polymer with free amino groups.
Surface area 150–200 m
2
/g.
Heavy metal adsorption,
flocculant in water treat-
ment and encapsulation
of bioactive agents.
[45]
Alginate
Algae Linear structure, anionic poly-
saccharide formed by blocks of
guluronic and mannuronic
acid. Surface area 10–50 m
2
/g.
Controlled release sys-
tems, encapsulation and
gel formation in water
treatment. [46]
Formation of biodegrada-
ble films, thickeners in
food and natural adhe-
sives.
Starch
Vegetable plants:
• Tubers
• Seeds of all plants
Granular structure composed
of amylose and amylopectin <
10 m
2
/g.
Emulsion stabilization,
encapsulation of bioac-
tive compounds and
films for sustainable
packaging.
[47]
Pectin
Fruits and vegetables
Branched structure
with galacturonic acid units.
Surface area <10 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[48]
Algae
Linear structure, anionic
polysaccharide formed
by blocks of guluronic
and mannuronic acid.
Surface area 10–50 m
2
/g.
Controlled release
systems, encapsulation
and gel formation in
water treatment.
[46]
Formation of
biodegradable films,
thickeners in food and
natural adhesives.
Starch
Processes 2025, 13, x FOR PEER REVIEW 5 of 30
3.1. Green Nanomaterials
Green nanomaterials are derived from renewable nat ural resources such as cellulose, chi-
tosan, lignin, alginate and pectin. Their nanoscale design endows them with unique proper-
ties, including a high surface-to-volume ratio, intrinsic biodegradability and versatile chemical
functionalization [38]. These properties make them highly effective in water treatment and
contaminant removal. Table 1 presents a comparison of various green materials from renew-
able natural resources, their origins, chemical structures, and application.
Table 1. Green nanomaterials from renewable natural resources of more common green materials.
Green Materials Origin Structure
/
Surface-Area Applications Reference
Cellulose nanofibers
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Bacteria
Nanoscale, fibrillar structure with
high surface area >300 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[40,41]
Lignin
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Grasses
Three-dimensional aromatic
structure with active functional
groups. Surface area 50–150 m
2
/g.
Adsorption of organic
pollutants, precursor in
carbon materials and re-
inforcement in polymers.
[44]
Chitosan
• Crustaceans
• Fungi
• Insects
• Some invertebrates
Linear structure, glucosamine
polymer with free amino groups.
Surface area 150–200 m
2
/g.
Heavy metal adsorption,
flocculant in water treat-
ment and encapsulation
of bioactive agents.
[45]
Alginate
Algae Linear structure, anionic poly-
saccharide formed by blocks of
guluronic and mannuronic
acid. Surface area 10–50 m
2
/g.
Controlled release sys-
tems, encapsulation and
gel formation in water
treatment. [46]
Formation of biodegrada-
ble films, thickeners in
food and natural adhe-
sives.
Starch
Vegetable plants:
• Tubers
• Seeds of all plants
Granular structure composed
of amylose and amylopectin <
10 m
2
/g.
Emulsion stabilization,
encapsulation of bioac-
tive compounds and
films for sustainable
packaging.
[47]
Pectin
Fruits and vegetables
Branched structure
with galacturonic acid units.
Surface area <10 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[48]
Vegetable plants:
•Tubers
•Seeds of all plants
Granular structure
composed of
amylose and
amylopectin < 10 m2/g.
Emulsion stabilization,
encapsulation of bioactive
compounds and films for
sustainable packaging.
[47]
Pectin
Processes 2025, 13, x FOR PEER REVIEW 5 of 30
3.1. Green Nanomaterials
Green nanomaterials are derived from renewable nat ural resources such as cellulose, chi-
tosan, lignin, alginate and pectin. Their nanoscale design endows them with unique proper-
ties, including a high surface-to-volume ratio, intrinsic biodegradability and versatile chemical
functionalization [38]. These properties make them highly effective in water treatment and
contaminant removal. Table 1 presents a comparison of various green materials from renew-
able natural resources, their origins, chemical structures, and application.
Table 1. Green nanomaterials from renewable natural resources of more common green materials.
Green Materials Origin Structure
/
Surface-Area Applications Reference
Cellulose nanofibers
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Bacteria
Nanoscale, fibrillar structure with
high surface area >300 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[40,41]
Lignin
Biomass lignocelluloses:
• Trees and shrubs
• Agricultural and
forestry waste
• Vegetable plants
• Grasses
Three-dimensional aromatic
structure with active functional
groups. Surface area 50–150 m
2
/g.
Adsorption of organic
pollutants, precursor in
carbon materials and re-
inforcement in polymers.
[44]
Chitosan
• Crustaceans
• Fungi
• Insects
• Some invertebrates
Linear structure, glucosamine
polymer with free amino groups.
Surface area 150–200 m
2
/g.
Heavy metal adsorption,
flocculant in water treat-
ment and encapsulation
of bioactive agents.
[45]
Alginate
Algae Linear structure, anionic poly-
saccharide formed by blocks of
guluronic and mannuronic
acid. Surface area 10–50 m
2
/g.
Controlled release sys-
tems, encapsulation and
gel formation in water
treatment. [46]
Formation of biodegrada-
ble films, thickeners in
food and natural adhe-
sives.
Starch
Vegetable plants:
• Tubers
• Seeds of all plants
Granular structure composed
of amylose and amylopectin <
10 m
2
/g.
Emulsion stabilization,
encapsulation of bioac-
tive compounds and
films for sustainable
packaging.
[47]
Pectin
Fruits and vegetables
Branched structure
with galacturonic acid units.
Surface area <10 m
2
/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[48]
Fruits and vegetables
Branched structure with
galacturonic acid units.
Surface area <10 m2/g.
Filtration membranes,
heavy metal adsorption
and reinforcement in
composite materials.
[48]
From Table 1, it can be observed that cellulose nanofibers are used as filtration mem-
branes, the adsorption of heavy metals and reinforcement in composite materials [
40
,
41
].
Lignin, with a three-dimensional aromatic structure and active functionality, has an area
of 50–150 m
2
/g, used for the adsorption of organic contaminants and as a precursor in
carbon materials [44]. Chitosan, a linear polymer with free amino groups, is prominent in
water treatment and encapsulation applications [
45
]. Alginate, derived from algae, with an
anionic polysaccharide structure and area of 10–50 m
2
/g, has applications in controlled
release and biodegradable adhesives [
46
]. On the other hand, starch (granular structure)
and pectin (branched structure) from plants and fruits, respectively, show a smaller surface
area (<10 m
2
/g), focusing on sustainable films, emulsion stabilization and food applica-
Processes 2025,13, 566 6 of 29
tions. These materials stand out for their versatility, sustainability and functionality, being
essential in sectors such as the environmental, food and advanced materials sectors.
3.2. Composite Materials
Composite materials combine the properties of various components to overcome the
limitations of individual green nanomaterials. This creates materials with enhanced proper-
ties, such as greater mechanical strength, thermal stability and optimized adsorption capaci-
ties. Combining biopolymers like chitosan with clays such as montmorillonite leverages the
high surface area of clays and the functional groups of biopolymers to achieve an efficient
adsorption of heavy metals and dyes, even under extreme conditions [
42
]. Hydrogels
composed of biopolymers and synthetic polymers, such as alginate with polyacrylamide,
combine the biodegradability of biopolymers with the mechanical strength of synthetic
polymers, making them ideal for large-scale industrial applications [
49
]. Incorporating
zinc oxide nanoparticles into biopolymer matrices significantly enhances the photocatalytic
degradation capacity for organic contaminants. Studies report reductions exceeding 80%
under UV irradiation [
46
]. These composites also offer antimicrobial properties, broadening
their applicability to potable water treatment systems [50].
Table 2provides a comparison between various green composite materials, their prop-
erties, and common uses. Biopolymers and clays, such as chitosan and montmorillonite,
have high adsorption and thermal stability, making them suitable for heavy metal and dye
remediation. Biopolymers and synthetic polymers, such as alginate and polyacrylamide,
offer mechanical strength and durability, making them ideal for large-scale water treat-
ment in industrial settings. Metal nanoparticles and biopolymers, such as zinc oxide and
biopolymers, have antimicrobial and photocatalytic properties, making them suitable for
the degradation of organic pollutants.
Table 2. Components, key properties and applications of the most common composite materials.
Composite Material Components Key Properties Main Applications References
Biopolymers and clays Chitosan, montmorillonite High adsorption,
thermal stability
Heavy metal
and dye remediation [42]
Biopolymers and synthetic polymers Alginate, polyacrylamide Mechanical strength, durability Industrial-scale water treatment [49]
Metal nanoparticles and biopolymers Zinc oxide, biopolymers Antimicrobial, photocatalytic Organic pollutant degradation [43,50]
In this regard, composite materials offer an interesting alternative in the design of
advanced solutions. These are developed by integrating biopolymers with other compo-
nents, such as clays, synthetic polymers and photocatalysts [
49
]. The synergy between
the components significantly improves adsorption, degradation and filtration properties,
optimizing their performance in specific applications. A clear example of this is the incor-
poration of zinc oxide nanoparticles into polymeric matrices, which has shown a notable
improvement in the degradation of organic contaminants under UV irradiation, evidencing
its potential in advanced water treatment technologies [
43
]. Likewise, the combination
of biopolymers with inorganic materials, such as montmorillonite, has been shown to
be effective in improving the thermal and mechanical stability of composite materials,
expanding their applicability in adverse environmental conditions [
51
]. On the other hand,
the functionalization of biopolymers with specific chemical groups has enabled the devel-
opment of composite materials with greater selectivity in the adsorption of heavy metals,
offering efficient solutions for the remediation of contaminated water [
52
]. These advance-
ments position composite materials as a key innovation in the development of advanced
technologies for water treatment, standing out for their high efficiency and adaptability to
current environmental challenges.
Processes 2025,13, 566 7 of 29
4. Applications of Advanced Green Materials in Water and
Wastewater Treatment
Advanced green materials, derived from renewable natural resources, prepared by
green synthesis or composite materials offer significant potential for sustainable water and
wastewater treatment. These materials possess unique properties that make them attractive
alternatives to conventional treatment methods. From a keyword search performed on the
ScienceDirect server using “green material” as well as the main key processes mentioned
above, 39,920 articles were found to date. Figure 1a shows the increase in research articles
over the last 20 years. Furthermore, Figure 1b shows the trend of the process used by green
material used for water and wastewater treatment systems; where most articles focus on
adsorption mechanisms and photocatalysis, other green material articles focus on the use
of renewable raw materials and biopolymer membranes.
Processes 2025, 13, x FOR PEER REVIEW 7 of 30
effective in improving the thermal and mechanical stability of composite materials, ex-
panding their applicability in adverse environmental conditions [51]. On the other hand,
the functionalization of biopolymers with specific chemical groups has enabled the devel-
opment of composite materials with greater selectivity in the adsorption of heavy metals,
offering efficient solutions for the remediation of contaminated water [52]. These advance-
ments position composite materials as a key innovation in the development of advanced
technologies for water treatment, standing out for their high efficiency and adaptability
to current environmental challenges.
4. Applications of Advanced Green Materials in Water and Wastewater
Treatment
Advanced green materials, derived from renewable natural resources, prepared by
green synthesis or composite materials offer significant potential for sustainable water
and wastewater treatment. These materials possess unique properties that make them at-
tractive alternatives to conventional treatment methods. From a keyword search per-
formed on the ScienceDirect server using “green material” as well as the main key pro-
cesses mentioned above, 39,920 articles were found to date. Figure 1a shows the increase
in research articles over the last 20 years. Furthermore, Figure 1b shows the trend of the
process used by green material used for water and wastewater treatment systems; where
most articles focus on adsorption mechanisms and photocatalysis, other green material
articles focus on the use of renewable raw materials and biopolymer membranes.
(a) (b)
Figure 1. Bibliographic review of articles of processes and principles utilized to treat water and
wastewater whit green material: (a) Exponential increase in publications that use green materials
for water treatment; (b) trend of the process used for green materials for water treatment.
Understanding the mechanisms that drive the remediation process using green ma-
terials is vital to identifying the key parameters that influence its effectiveness. This
knowledge allows for the selection of optimal green materials, improving their success in
pollutant degradation applications. Table 3 highlights advanced green materials for water
treatment, such as aerogels, nanoparticles, membranes and biofilms, using sustainable
feedstocks such as agricultural waste and expired oils. Key mechanisms, such as adsorp-
tion, photocatalysis and ultra-filtration, show outstanding efficiencies, for example, the re-
moval of Cr(VI) at 97%, Cd2+ at 98.46%, Pb2+ at 97.14%, acetaminophen at 75.4–84.6% and
Figure 1. Bibliographic review of articles of processes and principles utilized to treat water and
wastewater whit green material: (a) Exponential increase in publications that use green materials for
water treatment; (b) trend of the process used for green materials for water treatment.
Understanding the mechanisms that drive the remediation process using green materi-
als is vital to identifying the key parameters that influence its effectiveness. This knowledge
allows for the selection of optimal green materials, improving their success in pollutant
degradation applications. Table 3highlights advanced green materials for water treatment,
such as aerogels, nanoparticles, membranes and biofilms, using sustainable feedstocks such
as agricultural waste and expired oils. Key mechanisms, such as adsorption, photocatalysis
and ultra-filtration, show outstanding efficiencies, for example, the removal of Cr(VI) at
97%, Cd
2+
at 98.46%, Pb
2+
at 97.14%, acetaminophen at 75.4–84.6% and dyes at 90%. Hy-
brid materials, such as chitosan/polyaniline and functionalized membranes, stand out for
combining advanced properties and sustainability. However, challenges in this research
remain related to regeneration, economic viability and the potential environmental impact
of nanoparticles. To maximize their impact, a focus on industrial scale-up, stability and
hybrid applications, aligning with circular economy principles, is required.
Processes 2025,13, 566 8 of 29
Table 3. Advanced green materials in water and wastewater treatment.
Green Materials Pollutant%/Qmax mg/g Mechanism Raw Material/Form Reference
Biochar (BC)/reduced graphene oxide (rGO) Cr (VI) 15.6 mg/g: Adsorption Agricultural waste/aerogel [53]
Magnetite and zeolite (ZSM) /Fe3O4Acetaminophen
75.4–84.6% Photocatalysis Metal/nanoparticles [54]
Cuttlefish bone (CFB) Malachite green 92% Photocatalysis Particles [54]
BC
Tamarindus indica green magnetic Malachite green 5.577 mg/g methylene blue 3.055 mg/g Adsorption Seed/biochar [55]
(nM-BC) composite Malachite green 3.326 mg/g methylene blue 20.408 mg/g Adsorption Seed/biochar [56]
Soybean oil bio-based CHCL3—dyes Adsorption Expired oil [56]
NiFe2O4/Starch-g-poly(acrylic acid-co-acrylamide) (SANCH) Cr (VI) 99.7% Adsorption/photocatalysis Hydrogel [57]
TiO2/SANCH Cr (VI) 94.3% Adsorption/photocatalysis Hydrogel [58]
ZnCoFe2O4@Chitosan Tetracycline 92% Adsorption Nanoparticle [58]
CuO NPs on (Carica papaya L.) POME 66% Photocatalysis Peel biowaste/nanoparticle [59]
Cellulose/Graphene oxide (GO)/TiO2Methylene blue 93% Adsorption/photocatalysis Hydrogel [60]
Polysulfone Higher flux and rejection Ultra-filtration Membranes [61]
Green ceramic hollow with superhydrophobic and
superoleophilic surfaces Oil/water 99.9% and oil flux of 137.2 L/m Filtration Membrane [62]
BC-Fe/Zn Water permeance of 6.55 ±0.08 Filtration Membrane [63]
Nutraceutical Industrial Pepper Seed Spent (NIPSS) Brilliant green 144.6 mg/g Adsorption Nanoparticle [64]
Ca alginate/TiO2fibers Methyl orange 90% Ultra-filtration Membrane [65]
Chitosan and alginate composite (CSAL) Grey water turbidity < 5 NTU and TSS < 20 mg/L Filtration Membrane [66]
Carbon microspheres (CSn) Methylene blue 536.64 mg/g Adsorption Poplar waste/microspheres [67]
Corn leaf adsorbent Malachite green 91% Adsorption Corn leaves [68]
Zeolites with thermal activation Nickel 87%, copper and cadmium 99%, lead 100% Adsorption Particle [69]
Chitosan/carboxymethylcellulose polyelectrolytic complexes
(CHS/CMC macro-PECs) Cd2+ 98.46% and Pb2+ 97.14% Adsorption Particle [70]
CuO-NPs on (Portulaca oleracea) aqueous extract Tanned wastewater TSS 95.2%, TDS 86.7%, COD 64.4%,
BOD 91.4% Photocatalysis Nanoparticles [71]
Bacterial cellulose/γ-(2,3-epoxypropoxy) (BK) Oil/water separation dyes adsorption Adsorption Aerogel [72]
TiO2-cellulose nanocrystal Rhodamine B and methylene blue 97% Photocatalysis Aerogel [73]
Processes 2025,13, 566 9 of 29
Table 3. Cont.
Green Materials Pollutant%/Qmax mg/g Mechanism Raw Material/Form Reference
Copper sulfide (CuS) Methylene blue 95% and rhodamine B 92% Photocatalysis Hydrogel [74]
Grape residues (GR) with Azotobacter vinelandii NPs of 210–240 nm Photocatalysis Grape residues/coal [75]
Cellulose nanofiber (CNF) High selectivity and reusability Filtration Membranes [76]
Chitosan/polyaniline nanofibrous composite Blue 113,814.9 mg/g and orange dye 618.0 mg/g Filtration Membranes [77]
Thin-film nanofibrous composite with barium alginate
(TFNC with BaAlg NF)
Permeation flux 112.5 ±1.8 L·m/h. with a tensile strength as
8.17 Mpa Filtration Membrane [78]
CN PFs
Oil–water separation and photocatalytic degradation properties
Filtration Membrane [79]
Butanediol succinate (PBS) TOC and nitrate 95% Adsorption Biofilm [80]
Pistacia soft shell (PSS) COD 67% and turbidity 87% Adsorption Coal [81]
Processes 2025,13, 566 10 of 29
Regarding specific nanomaterials, cellulose nanofibers (CNFs) stand out due to their
natural origin, derived from materials such as wood, cotton and hemp obtained through
mechanical, chemical or enzymatic treatments [
41
]. These nanofibers, with a high aspect
ratio, possess a large surface area, high tensile strength and abundant hydroxyl groups,
making them particularly valuable for water treatment [
40
]. Their utility includes the
adsorption of heavy metal ions and organic contaminants, as well as serving as building
blocks for high-performance filtration membranes [
82
]. A relevant example is the function-
alization of CNFs with carboxyl groups, which significantly increases the adsorption of
metals such as lead and cadmium, making these nanofibers a useful tool for remediating
contaminated water [
39
]. Moreover, the integration of CNFs into polymeric matrices has
resulted in membranes with superior mechanical properties and higher filtration efficiency,
expanding their applicability in advanced water treatment systems [6].
As for chitosan, this linear polysaccharide derived from chitin present in crustacean
shells and insect exoskeletons is characterized by its excellent biocompatibility, biodegrad-
ability and adsorption capacity [
41
]. The presence of amino and hydroxyl groups in its
structure facilitates its effective binding to contaminants such as heavy metal ions, dyes
and other organic compounds [
83
]. This biopolymer is used as an adsorbent, or flocculant,
or in the manufacturing of composite materials to improve water treatment processes [
83
].
Additionally, recent research highlights that chitosan membranes modified with graphene
oxide nanoparticles exhibit an outstanding capacity for the adsorption of organic contami-
nants, reinforcing their potential in water purification [
58
,
84
]. Similarly, the combination
of chitosan with inorganic materials such as montmorillonite has enabled the creation of
compounds with improved mechanical and thermal properties, increasing their viability
under demanding conditions [85].
In parallel, bio-based nanomaterials such as pectin, lignin and chitin nanofibers also
represent sustainable alternatives in water treatment. Thanks to their large specific surface
area, biodegradability, and the presence of functional groups, these materials are adapted
to various applications, such as the selective adsorption of specific contaminants or their
incorporation into advanced filtration systems [
86
]. The integration of biopolymers like
chitosan with clays, such as bentonite or kaolinite, has proven to be an effective strategy
for improving the adsorption of heavy metals and dyes. This synergistic effect is due to
the large specific surface area of the clays and the functional groups, such as amino and
hydroxyl, present in the biopolymer. These properties significantly increase the adsorption
sites and strengthen the interactions with contaminants. Additionally, this combination
improves mechanical stability and allows for the reuse of the composite material, increas-
ing its efficiency in treating contaminated water [
42
]. In a complementary approach, the
combination of biopolymers such as chitosan or alginate with synthetic polymers, such as
polyacrylamide or polyvinyl alcohol, has allowed for the development of hydrogels with
superior mechanical and adsorption properties. The biodegradability and biocompatibility
of biopolymers, coupled with the stability and processability of synthetic polymers, gener-
ate a synergistic effect that improves the performance of these materials. This approach
results in an increase in adsorption capacity, controlled swelling behavior and greater
viability for reuse in practical applications [49].
Recent studies have explored the incorporation of metallic nanoparticles into biopoly-
mer matrices to enhance their adsorption properties and antimicrobial activity. A notable
example is the integration of silver nanoparticles into chitosan hydrogels, which has shown
high efficacy in the removal of bacteria and organic contaminants [
50
]. Similarly, the addi-
tion of zinc oxide nanoparticles to alginate hydrogels has increased the adsorption capacity
of heavy metals, as well as improving the material’s performance under adverse environ-
mental conditions, highlighting its potential in advanced water purification systems [
87
].
Processes 2025,13, 566 11 of 29
On the other hand, titanium dioxide nanoparticles incorporated into polymeric matrices
have proven to be highly efficient in the photocatalytic degradation of persistent organic
pollutants, reinforcing their usefulness in environmental remediation applications [41].
The functionalization of biopolymers with magnetic nanoparticles, such as iron ox-
ide, has enabled the development of composite materials with advanced separation and
recovery capabilities. These compounds stand out for their mechanical and chemical sta-
bility, which extends their lifespan and makes them ideal for wastewater treatment [
28
].
Likewise, the combination of metallic nanoparticles with biocompatible biopolymers has
optimized both the adsorption capacity and durability of these materials, consolidating
them as practical and sustainable alternatives in water treatment applications [
87
]. The
integration of biopolymers like cellulose or chitosan with photocatalysts, such as TiO
2
or ZnO, has been proven to be highly effective in improving the degradation of organic
contaminants through photocatalytic processes [
12
]. This synergistic effect is due to the
adsorption capacity of the biopolymer and the photocatalytic activity of the photocatalyst,
resulting in a greater adsorption and degradation of contaminants [
84
]. Additionally, an
improved treatment efficiency is observed due to a faster degradation kinetics, a reduction
in electron–hole pair recombination and a greater stability of the composite material [83].
Furthermore, recent research has explored the functionalization of biopolymers to im-
prove their interaction with photocatalysts. This includes the addition of specific functional
groups that increase affinity for contaminants and enhance electron transfer during photo-
catalytic processes [
88
]. This approach has generated composite materials that are highly
effective in remediating water contaminated with a wide range of organic compounds.
Chitosan-based nanomaterials have emerged as a promising avenue for the removal of
pathogens in drinking water treatment. Chitosan possesses inherent antimicrobial prop-
erties attributed to its cationic nature and its ability to disrupt bacterial cell walls. This
mechanism of action makes chitosan-based nanomaterials effective against a wide range of
waterborne pathogens, including bacteria, fungi and viruses [
89
–
91
]. Additionally, chitosan
is biocompatible and biodegradable, ensuring minimal environmental impact when used
in water treatment applications [22].
Silver nanoparticles have been extensively studied for their potent antimicrobial ac-
tivity. Silver has long been recognized for its disinfectant properties, and its effectiveness
is amplified when engineered into nanoparticles at the nanoscale. The high surface-area-
to-volume ratio of silver nanoparticles enhances their interaction with microorganisms,
disrupting cellular functions and effectively neutralizing a wide range of pathogens in
drinking water [
82
,
92
,
93
]. Additionally, some studies have explored the incorporation of
silver nanoparticles into chitosan matrices to enhance the adsorption properties and antimi-
crobial activity of composite materials. For instance, the integration of silver nanoparticles
into chitosan hydrogels has demonstrated remarkable efficacy in the removal of bacte-
ria and organic contaminants [
94
]. Moreover, the functionalization of biopolymers with
specific chemical groups has enabled the creation of composite materials with improved
selectivity for the adsorption of heavy metals, offering more efficient solutions for the
remediation of contaminated water [52].
5. Processes and Principles Utilized to Treat Water and Wastewater
The mechanisms that green materials follow involve several key processes (Table 3),
which can be categorized as follows: (i) adsorption process involving electrostatic in-
teractions or physical adsorption [
67
], chemical bonding or chemisorption [
68
] or ion
exchange [
70
]; (ii) as a photocatalytic agent with nanocomposites based on biopolymers
with metal oxides [
73
], reduction and oxidation reactions [
71
] or as a template reducing
agent for the synthesis of metal nanoparticles [
95
]. Green materials can also used as
Processes 2025,13, 566 12 of 29
(iii) biopolymeric membrane such as membranes based on cellulose [
76
], chitosan [
77
] and
alginate [
78
] or composite membranes combined with various nanomaterials for different
qualities of phase separation, such as micro-membranes [
73
], ultra-membranes [
79
] or
nanomembranes [
96
]; (iv) applications of biopolymers used as raw materials as natural
coagulants [
81
], as a template matrix for hydrogel [
74
] or aerogel [
72
] and as biopolymer
matrices for the growth of microorganisms [
75
] or fungi [
97
] for pollutant degradation in
bioreactors [
80
]. The theoretical principles of the mechanisms and processes that drive the
green remediation process are presented below, followed by a brief discussion of the most
recent advances in each key process and why this technique has been investigated.
5.1. Adsorption
Adsorption involves a mass transfer process in which substances accumulate at the
interface with a variety of gas–liquid, gas–solid, liquid–solid or liquid–liquid interfaces.
These properties of adsorbates (substance that is adsorbed) and adsorbents (adsorbent
material) indicate the mechanism of the adsorption process. If this interaction has a physical
nature such as molecules adsorbed on a solid surface, the attractive interactions are Van der
Waals forces and is called physisorption. If this occurs between the chemical bond of the ad-
sorbed molecules and the solid surface, the process is called chemisorption. Both processes
can occur alternatively or simultaneously, they can be affected by thermodynamics and the
kinetic model/equation obtained is used to describe the adsorption mechanism [98,99].
According to Figure 1a, adsorption is the most-studied mechanism in the publications
reported in recent years. This is corroborated in Table 3; therefore, the basic concepts of how
to interpret adsorption in green materials will be explained below. Figure 2illustrates the
adsorption mechanisms that occur in a porous material and its interaction with different
contaminants, such as dyes and heavy metals. Among the key processes is pore filling,
where cavities in the material allow the accommodation of contaminants, maximizing
the adsorption capacity. In addition, hydrogen bonding interactions strengthen the bond
between adsorbed molecules and the functional groups of the material, increasing the
chemical affinity. Meanwhile,
π
-
π
interactions play a crucial role in the capture of aromatic
compounds thanks to the interaction between the
π
systems of the material and those
of the adsorbed molecules. Van der Waals forces are also present, which involve weak
physical attractions, useful for retaining non-polar or slightly polar molecules. Finally,
electrostatic adsorption is based on the attraction between the opposite charges of the
functional groups of the material and the contaminants, a particularly effective mechanism
for adsorbing ions and charged molecules. These mechanisms, which combine chemical
and physical interactions, highlight the versatility of the adsorbent material, making it
ideal for applications in environmental remediation, water purification and the removal
of organic and inorganic contaminants from various matrices [
100
]. To discuss the data
obtained from the green adsorbents, the amount of the total uptake of contaminants in
equilibrium (Qe) was calculated using the mass balance Equation (1).
Qe=(C0−Ce)V
M(1)
where Q
e
(mg/g) represents the equilibrium of total uptake, C
0
(mg/L) and C
e
(mg/L)
indicate the initial and equilibrium concentration of the pollutant in liquid phase, V(L)
indicates volume and M(g) represents the mass of the adsorbent [
99
]. One of the most
representative models reported in the literature are the Langmuir adsorption model [101].
This isotherm states that the adsorption process occurs at binding sites on the surface of
Processes 2025,13, 566 13 of 29
adsorbent, and this then makes a monolayer on it, with no interaction between, as observed
in Langmuir Equation (2).
Qe=QmKLCe
1+KLCe(2)
Processes 2025, 13, x FOR PEER REVIEW 12 of 30
removal of organic and inorganic contaminants from various matrices [100]. To discuss
the data obtained from the green adsorbents, the amount of the total uptake of contami-
nants in equilibrium (Qe) was calculated using the mass balance Equation (1).
Figure 2. Schematic diagram of adsorption mechanism [100].
𝑄= (𝐶−𝐶
)𝑉
𝑀 (1)
where Qe (mg/g) represents the equilibrium of total uptake, C0 (mg/L) and Ce (mg/L) indi-
cate the initial and equilibrium concentration of the pollutant in liquid phase, V (L) indi-
cates volume and M (g) represents the mass of the adsorbent [99]. One of the most repre-
sentative models reported in the literature are the Langmuir adsorption model [101]. This
isotherm states that the adsorption process occurs at binding sites on the surface of adsor-
bent, and this then makes a monolayer on it, with no interaction between, as observed in
Langmuir Equation (2).
𝑄= 𝑄𝐾𝐶
1+𝐾
𝐶 (2)
The Freundlich isotherm model [99], which describes multilayer and heterogeneous
adsorption, indicating the presence of monolayer and interaction between the surface
characterized for chemisorption, is observed in Freundlich Equation (3).
𝑄= 𝐾𝐶
(3)
where Qe (mg/g) indicates adsorption capacity at equilibrium in the solid phase, Qm (mg/g)
represents the maximum quantity of adsorbed molecules on to the surface, Ce (mg/L) rep-
resents the concentration of the molecules at equilibrium, KL (L/mg) represents the Lang-
muir constant and KF (mg/g) and 1/n are the Freundlich constant, which is an indicator of
heterogeneity and intensity [102].
The Temkin isotherm model [99] commonly analyzes the affinity between adsorbent
and adsorbate. Therefore, this model usually explains or suggests the chemisorption for
fiing the data, as observed in Temkin Equation (4).
𝑄= 𝑅𝑇
𝑏ln (
𝐴
𝐶) (4)
Figure 2. Schematic diagram of adsorption mechanism [100].
The Freundlich isotherm model [
99
], which describes multilayer and heterogeneous
adsorption, indicating the presence of monolayer and interaction between the surface
characterized for chemisorption, is observed in Freundlich Equation (3).
Qe=KFC1/n
e(3)
where Q
e
(mg/g) indicates adsorption capacity at equilibrium in the solid phase, Q
m
(mg/g) represents the maximum quantity of adsorbed molecules on to the surface, C
e
(mg/L) represents the concentration of the molecules at equilibrium, K
L
(L/mg) represents
the Langmuir constant and K
F
(mg/g) and 1/nare the Freundlich constant, which is an
indicator of heterogeneity and intensity [102].
The Temkin isotherm model [
99
] commonly analyzes the affinity between adsorbent
and adsorbate. Therefore, this model usually explains or suggests the chemisorption for
fitting the data, as observed in Temkin Equation (4).
Qe=RT
bT
ln (ATCeq)(4)
where
Qe
(mg/g) indicates the maximum adsorption capacity, R represents the universal
gas constant, T is the absolute temperature and AT,bTrepresents constants.
Other models are also used to describe this phenomenon, such as Brunauer, Em-
mett, and Teller isotherm [
103
], Redlich–Peterson isotherm or Harkins–Jura and Halsey
isotherms [
101
]. A common analysis setup in terms of modeling the physicochemical
process of adsorption process is based on that in which the amount of adsorbate that has
been adsorbed on the surface of the adsorbent (mass) is expressed as Q
e
, which corresponds
with the thermodynamic equilibrium. Therefore, the data analysis consists of fitting the
experimental data measuring the evolution of adsorbate concentration. This adsorption
Processes 2025,13, 566 14 of 29
kinetics uses the Q
e
equilibrium value as the parameter of the experimental data, and then
k1 is found from the fitting.
(a) This model is the Lagergren Equation (5), commonly called the pseudo-first order
model. This expression is after integration.
Qt=Qe1−e−k1t(5)
(b) A second model, called the pseudo-second order model, as in Equation (6), uses
the same data analysis, and the fitting results are commonly better adjusted; this expression
is also after integration. The experimental data can use linear fitting.
Qt=K2Q2
et
1+K2Qe(6)
where Q
t
(mg/g) is the amount of absorption capacity at a time, and Q
e
(mg/g) is the
number of absorbed pollutants at equilibrium, t (min). The fitting parameters were used to
find coefficients K
1
or K
2
(1/min) who were dependent on the operational variables and
represent a constant rate for the first and second-order adsorption process.
(c) The McKay model, Equation (7), is derived from the analyzed effect of the stirring
on kinetics. It corresponds with analyzing the evolution of the bulk concentration and mass
transfer from the solution, with the adsorption process being the slowest onto the surface.
lnC
C0
−1
1+KM=lnKM
1+K M −1+KM
KMhSt (7)
where Srepresents the total adsorbent particles, Kis the linear isotherm constant and h
indicates the mass transfer coefficient [99].
(d) The Elovich model, Equation (8), assumes a time dependence of mass transfer to
be usually logarithmic, where the constants are related to adsorption and desorption rates.
This model is also commonly used.
Qt=ln (αβ)+ln (t)
β(8)
where αindicates desorption constant, and βis the initial adsorption rate [99]
Another important indicator of the nature of the adsorption process on green materials
is their thermodynamics. This indicates that it is spontaneous in most cases (
∆
G
◦
< 0)
with regard to the interaction of the heavy metal ions with the green adsorbents. Also, its
noted that with the increase in temperature, adsorption increased, indicating a removal
process with endothermic characteristics [
104
]. An additional important factor with green
adsorbents is their pH; green adsorbents are favorable for dye uptake, with pH values
above the pH of the point of zero charge (pHzpc) being most suitable. The chemical
constitution of surface functional groups promotes the adsorption process, although the
absorption of anionic dyes occurs at lower pH levels [105,106].
Hao et al. fabricated CSn carbon microspheres from the raw material of factory poplar
waste. The adsorption isotherm was described by Langmuir with a maximum adsorption
capacity of 536.64 mg/g; the kinetics fitted a pseudo second order for methylene blue [
67
].
Fadhel et al. decolorized malachite green with adsorbent material obtained from corn
leaves. Its adsorption isotherm was described by the Freundlich model, with a maximum
uptake of 91%, and the kinetics fitted a pseudo second order [
68
]. Kuldeyeb et al. reported
the improved adsorption capacity of zeolites by thermal activation, with a furnace treatment
at 550
◦
C, for 2 h. They reported a heavy metal uptake of 87% for nickel, 99% for cooper
and cadmium and 100% for lead [
69
]. Ferreira et al. fabricated granular macroscopic
Processes 2025,13, 566 15 of 29
chitosan/carboxymethylcellulose polyelectrolytic complexes (CHS/CMC macro-PECs).
These were tested with dyes, Cd
2+
and Pb
2+
. The adsorption isotherm was described by
Langmuir, revealing a maximum adsorption capacity of 98.46% and 97.14%, and the kinetics
also fitted a pseudo second order. The desorption assays showed that CHS/CMC macro-
PECs can be regenerated after the adsorption process [
70
]. These examples demonstrate the
variability in pollutant removal, as well as the important diversity of adsorbents, and their
use as raw materials, in the synthesis process and the generation of chemical complexes.
5.2. Photocatalysis
Photocatalysis is the second-most-studied mechanism in the publications reported
in recent years (Figure 1b) because it studies green materials functionalized with photo-
catalytic nanoparticles that are very efficient in removing contaminants from water, such
as TiO
2
, gold nanoparticles and other metals (Table 3). The photocatalysis degradation
involves photons and a catalyst; this occurs on the energy levels on some materials that are
very close, and they allow electrons of the highest energy band or conduction band (CB) to
be fulfilled with empty holes from a lower band, in this case, a valence band (VB). On liquid
water, it can form an OH radical through the oxidation of the adsorbed water molecule
by a VB hole (h
+
); this is where the material is photoexcited [
107
,
108
]. The degradation of
contaminants in wastewater, under sunlight, and some free radicals such as superoxides
(
•
O
2−
) and hydrogen peroxides (
•
OOH) occurred after interacting with this excited e
–
in
energy levels CB with O
2
, whereas hydroxyl free radicals (
•
OH) were formed due to their
interaction of h+ with H2O [109] (Figure 3).
Processes 2025, 13, x FOR PEER REVIEW 14 of 30
[67]. Fadhel et al. decolorized malachite green with adsorbent material obtained from corn
leaves. Its adsorption isotherm was described by the Freundlich model, with a maximum
uptake of 91%, and the kinetics fied a pseudo second order [68]. Kuldeyeb et al. reported
the improved adsorption capacity of zeolites by thermal activation, with a furnace treat-
ment at 550 °C, for 2 h. They reported a heavy metal uptake of 87% for nickel, 99% for
cooper and cadmium and 100% for lead [69]. Ferreira et al. fabricated granular macro-
scopic chitosan/carboxymethylcellulose polyelectrolytic complexes (CHS/CMC macro-
PECs). These were tested with dyes, Cd2+ and Pb2+. The adsorption isotherm was described
by Langmuir, revealing a maximum adsorption capacity of 98.46% and 97.14%, and the
kinetics also fied a pseudo second order. The desorption assays showed that CHS/CMC
macro-PECs can be regenerated after the adsorption process [70]. These examples demon-
strate the variability in pollutant removal, as well as the important diversity of adsorbents,
and their use as raw materials, in the synthesis process and the generation of chemical
complexes.
5.2. Photocatalysis
Photocatalysis is the second-most-studied mechanism in the publications reported in
recent years (Figure 1b) because it studies green materials functionalized with photocata-
lytic nanoparticles that are very efficient in removing contaminants from water, such as
TiO2, gold nanoparticles and other metals (Table 3). The photocatalysis degradation in-
volves photons and a catalyst; this occurs on the energy levels on some materials that are
very close, and they allow electrons of the highest energy band or conduction band (CB)
to be fulfilled with empty holes from a lower band, in this case, a valence band (VB). On
liquid water, it can form an OH radical through the oxidation of the adsorbed water mol-
ecule by a VB hole (h+); this is where the material is photoexcited [107,108]. The degrada-
tion of contaminants in wastewater, under sunlight, and some free radicals such as super-
oxides (•O2–) and hydrogen peroxides (•OOH) occurred after interacting with this excited
e– in energy levels CB with O2, whereas hydroxyl free radicals (•OH) were formed due to
their interaction of h+ with H2O [109] (Figure 3).
Figure 3. Schematic diagram of photocatalytic mechanism [109].
Figure 3. Schematic diagram of photocatalytic mechanism [109].
Eid et al. fabricated CuO-NPs on an aqueous extract of Portulaca oleracea, with high
catalytic activity. They decolorated tanned wastewater under sunlight with a dosage of
2.0 mg/mL and obtained a decrease in the values of total suspended solids (TSSs) 95.2%,
total dissolved solids (TDSs) 86.7%, chemical oxygen demand (COD) 64.4% and biological
oxygen demand (BOD) 91.4% [
71
]. Hu et al. described a green method to prepare a
versatile bacterial cellulose/
γ
-(2,3-epoxypropoxy) propytrimethoxysilane trimethoxysilane
composite aerogel called BK aerogel. This improved the elasticity, which could reach 87.8%,
and had over 50 times the compression; also, he proposed this be used for dye adsorption
and oil water separation [
72
]. Gallegos-Cerda et al. fabricated a cellulose aerogel with TiO
2
-
CNTs. With this composite, they evaluated the degradation of dyes (with rhodamine B and
Processes 2025,13, 566 16 of 29
methylene blue) on aqueous solution, with a photocatalytic removal (>97%), after 110 min
of UV irradiation. These results indicated that cellulose aerogels coupled with nanofillers
can be enabled to generate useful material for wastewater treatment [
73
]. Wang et al.
described a cellulose hydrogel integrated with copper sulfide (CuS) and epichlorohydrin
to increase mechanical strength. The hydrogels with a CuS loading of 30 wt% showed a
photocatalytic degradation of 95% for methylene blue and 92% for rhodamine B [
74
]. Andler
et al. used grape residues. These were used as a carbon source in Azotobacter vinelandii,
and these cultures were then used for PHB production and nanoparticle synthesis. The
formation showed high stability, with particle size on the interval of 210–240 nm [
75
]. These
examples were chosen to indicate how green synthesis has been studied for the production
of photocatalytic nanoparticles with plant-based extracts and also how these processes can
in turn be more friendly processes or methods than those conventionally used.
5.3. Polymeric Membranes and Filtration
Biopolymer membranes and filtration are the third-most-studied mechanism in the
publications reported in recent years (Figure 1b) due to the great interest in replacing
synthetic membranes with organic membranes. Membranes are a separation technology
that is cost-effective as a wastewater treatment. Equally harmless, they allow the simpler
classification of organic and inorganic membranes, where polymer membranes and natural
membranes can be categorized. On the classification of pore size, there are four types:
reverse osmosis RO (0.0001–0.001 m) capable of removing, for example, ions, dissolved
substances and particles; nano-filtration NF (0.0005–0.01 m) for organic matter and divalent
ions; ultra-filtration UF (0.005–0.5 m) effectively remove bacteria, viruses and small colloids;
and micro-filtration MF (0.05–1.0 m) remove macromolecules and larger colloids. Figure 4
shows an illustration of the filtration mechanism, which is a process in which solid particles
are removed from a fluid by using a filter medium (membranes) that allows the fluid to
pass through it but retains the solid particles (contaminants).
Processes 2025, 13, x FOR PEER REVIEW 16 of 30
Figure 4. Schematic diagram of filtration mechanism.
Some disadvantages of natural membranes are the capability to create linkage-col-
ored chemicals and to maintain mechanical strength and constant permeation flux; there-
fore, much of the investigation of natural membranes is regarding the outcome of these
maers [82]. However, these biopolymer-based membranes can offer an aractive versa-
tility, such as cellulose, chitosan, alginate, corn starch, etc., which exhibit excellent adsorp-
tion capacities, biocompatibility and biodegradability. So, recently incorporated nano-
fillers have enhanced their mechanical strength, or improved stability. Therefore, these
nanocomposites made with nanofillers have the maer to expand this application to tai-
lored functionalities [84,110]. Some examples of this search are provided below.
Pak et al. prepared cellulose nanofiber (CNF) membranes. Hydrochar was chemically
bonded to enhance the durability of CNF, and it also demonstrated high selectivity and
reusability [76]. Liu et al. fabricated chitosan/polyaniline nanofibrous composite mem-
branes, with an average diameter range from 300 to 200 nm; these exhibited adsorption
capacities of 814.9 mg/g and 618.0 mg/g for blue 113 and orange dye, respectively, and
thermodynamics indicated that it was a spontaneous process with the generation of a
monolayer on the membrane [77]. Chen et al. proposed an interlayer-regulated thin-film
nanofibrous composite (TFNC). This was obtained by coating barium alginate (BaAlg) on
the polyacrylonitrile substrate. This hydrogel interlayer, with barium ions, had higher sta-
bility, hydrophilicity and separation performance. This composite of NF membrane in-
creased mechanical properties, with a tensile strength of 8.17 MPa. It also could display
a permeation flux of 112.5 ± 1.8 L⋅m/h, being an NF membrane with development potential
[78]. Yin et al. fabricated a pulp/cellulose nanofiber (CNF) membrane with superhydro-
phobic and antibiotic adhesion, oil–water separation and photocatalytic degradation
properties. This CNF membrane was fabricated by the coating method. This process also
is environmentally benign and practicable, a facile multifunctional material for several
functions in wastewater treatment [79].
5.4. Raw Material
As we mentioned, due to its intrinsic characteristics, as well as the need to search for
simpler methods of generating materials, much research has been directed towards car-
rying out material synthesis processes to be used as templates, as a composite matrix or
even as raw material for the adsorption process, or flocculants, etc. So, the use of green
Figure 4. Schematic diagram of filtration mechanism.
Some disadvantages of natural membranes are the capability to create linkage-colored
chemicals and to maintain mechanical strength and constant permeation flux; therefore,
much of the investigation of natural membranes is regarding the outcome of these mat-
ters [
82
]. However, these biopolymer-based membranes can offer an attractive versatility,
such as cellulose, chitosan, alginate, corn starch, etc., which exhibit excellent adsorption
Processes 2025,13, 566 17 of 29
capacities, biocompatibility and biodegradability. So, recently incorporated nanofillers have
enhanced their mechanical strength, or improved stability. Therefore, these nanocomposites
made with nanofillers have the matter to expand this application to tailored functionali-
ties [84,110]. Some examples of this search are provided below.
Pak et al. prepared cellulose nanofiber (CNF) membranes. Hydrochar was chemically
bonded to enhance the durability of CNF, and it also demonstrated high selectivity and
reusability [
76
]. Liu et al. fabricated chitosan/polyaniline nanofibrous composite mem-
branes, with an average diameter range from 300 to 200 nm; these exhibited adsorption
capacities of 814.9 mg/g and 618.0 mg/g for blue 113 and orange dye, respectively, and
thermodynamics indicated that it was a spontaneous process with the generation of a
monolayer on the membrane [
77
]. Chen et al. proposed an interlayer-regulated thin-film
nanofibrous composite (TFNC). This was obtained by coating barium alginate (BaAlg) on
the polyacrylonitrile substrate. This hydrogel interlayer, with barium ions, had higher
stability, hydrophilicity and separation performance. This composite of NF membrane
increased mechanical properties, with a tensile strength of 8.17 MPa. It also could dis-
play a permeation flux of 112.5
±
1.8 L
·
m/h, being an NF membrane with development
potential [
78
]. Yin et al. fabricated a pulp/cellulose nanofiber (CNF) membrane with super-
hydrophobic and antibiotic adhesion, oil–water separation and photocatalytic degradation
properties. This CNF membrane was fabricated by the coating method. This process also
is environmentally benign and practicable, a facile multifunctional material for several
functions in wastewater treatment [79].
5.4. Raw Material
As we mentioned, due to its intrinsic characteristics, as well as the need to search for
simpler methods of generating materials, much research has been directed towards carrying
out material synthesis processes to be used as templates, as a composite matrix or even as
raw material for the adsorption process, or flocculants, etc. So, the use of green materials
covers an increasingly diverse range of approaches; some examples of this investigation are
provided below, which may limit the interests in technological innovation and the ability
to generate synergy in many processes.
Wu et al. investigated the used of butanediol succinate (PBS) as a carbon source biofilm
for nitrate removal from aqueous solution and total organic carbon (TOC): an average
removal efficiency of 95% of nitrate was achieved [
80
]. Nazari et al. proposed the potential
application of the Pistacia soft shell (PSS) as a natural flocculant for wastewater treatment,
with a removal of 67% of COD and 87% of turbidity demonstrating the feasibility; also,
the dosage was optimized at 2 g/L [
81
]. Al-Mafarjy et al. synthetized gold nanoparticles
(AuNPs) using the leaf extract of Coleus scutellarioides (L.). The study investigated the
potential cytotoxic effects, using the MTT assay [
95
]. Andler et al. used grape residues;
these were used as carbon source in Azotobacter vinelandii OP, and these cultures were then
used for PHB production and subsequent nanoparticle synthesis. A biomass concentration
of 2.9 g/L and a PHB accumulation of up to 37.7% w/wwere obtained [
75
]. Wikandari
et al. investigated the potential use of residual water in a tempeh factory for filamentous
fungal biomass production; the results showed that the first boiling yeast extract gave the
highest mycoprotein biomass, which contained 19.44% (w/w) protein with a high crude
fiber content. Furthermore, the interest in using green materials where we circulate the
use for them, as well as producing environmentally friendly materials, has grown. The
term biodegradation requires, to be considered biodegradable, the degradation of 90% of
the mass of the material be possible; this is converted for other low-mass products, such
as CO
2
or H
2
O, and biomass that naturally would be assimilated for microorganisms. In
environmental conditions, this would occur at approximately 6 months [
111
]. Therefore, to
Processes 2025,13, 566 18 of 29
assess the biodegradability of the materials produced, other factors like disposal systems
and the environment conditions nearby must be taken into count. One specific manner that
is important to consider is the intrinsic factors such as crystallinity, molecular weight or
chemical structure for every polymer tested. Standard norms exist, as do measurements
for plastic biodegradation; in summary, ASTM D5988-18 [112] measures the CO2released
by microorganisms, indicating the degree and rate of the aerobic biodegradability of the
plastic material [111].
6. Modeling Applied to Performance of Green Materials
One of the most recognized modeling and optimization techniques to address the
analysis of a new material and its future impact is the use of response surface methodology
(RSM) since it allows for efficient statistical analysis by obtaining and calculating ANOVA,
proposing empirical models that fit the description of the phenomenon; obtaining 2D or 3D
graphics to accurately delimit the areas where there is a greater impact on the reference
parameters of the system; and obtaining optimal solutions that propose the best relationship
of the process variables to increase the performance of the expected output. There were
recent cases of research that used these methods to model and optimize their systems based
on new green materials, which proposes the use of nanomaterials with green synthesis
from biohydrometallurgical leachates of electronic waste [
113
]. More cases were reported
in the literature such as iron oxide nanoparticles for the removal of methylene blue and
methyl orange from textile wastewater, achieving under-optimal-condition removals above
97% [
89
]. The synthesis of copper oxide nanoparticles, CuO NPs, from the leaf extract of
Eucalyptus globulus reported good results by optimizing the operating parameters of the
material in the absorption of methyl orange, but the operational costs to take these results
beyond the laboratory were not reported [
114
]. Green syntheses of various nanoparticle
matrices have been recently studied by developing systems based on chitosan [
115
], zero-
valent steel [
12
], zero-valent copper nanomolecules [
116
] and carbon encapsulations of
cocoa cobs functionalized with tetrasodium salt (EDTA) [
117
], reporting good removals of
added contaminants but leaving occasional reports that validate the economic scope for
these studies, which represents a very relevant unknown for the future. Likewise, one of
the main disadvantages of MSR is its inoperability due to uncontrollable decisive factors
and that fits well between the proposed model and the experimental results that are not
always achieved [117].
Artificial neural networks (ANNs) are another computational technique that is in-
spired by the processes of the human brain to process a database, which by adjusting the
weights of the network, the desired output response is obtained. Among the various models
that exist for ANN, the system based on forward propagation seems to be established as
the most appropriate to study various chemical processes [
118
]. The advantages of this
technique is that it does not require in-depth knowledge of the parameters that govern
the process or phenomenon to be studied; significant models can also be obtained with
robust adjustments and very small estimation errors, along with a relatively low compu-
tational cost [
118
,
119
]. The development of artificial intelligence to model and optimize
systems based on green synthesis has gained greater momentum in recent years with
works reported in the literature, such as iron nanoparticles from black tea for the treatment
of municipal wastewater [
119
] and green cobalt synthesis [
120
] for the prediction of the
size of silver nanoparticles [
121
], obtaining silver nanoparticles from Terminalia bellerica
seed extract [
122
] as well as copper oxide (CuO) nanoparticles from biohydrometallurgical
leachates of electronic waste [
113
]. In these presented works, the ability of the ANN to
obtain models with statistical fits close to R
2
and close to R
1
are highlighted and thus help
Processes 2025,13, 566 19 of 29
to discard or further support the experimental matrix proposed for the representation of
the phenomenon [117].
Artificial intelligence (AI) is revolutionizing the design and optimization of green
materials in diverse areas such as construction [
123
], cosmetics [
124
], biomaterials [
125
]
and water treatment [
89
,
113
]. These tools allow chemical configurations and physical
properties to be explored efficiently, overcoming the limitations of traditional trial-and-
error methods. The advantages of artificial intelligence in green material design include its
ability to significantly reduce time and costs by automating processes and exploring broad
design spaces, achieving remarkable efficiency [
126
]. The main disadvantages of artificial
intelligence in green material design include the reliance on large and well-structured data
sets, which can limit the applicability of the models; the high computational complexity that
demands significant resources for their implementation; and the difficulties in predicting
complex interactions in multi-component systems, such as in cosmetic formulations or
water treatment materials [
89
,
124
,
126
]. In addition, the models are often interpretively
opaque, making it difficult to understand the underlying scientific principles, and, in
some cases, they generate theoretically optimal solutions that are not feasible in practical
applications [
117
,
119
,
125
]. Although the application of AI in the synthesis of green materials
is in its early stages, its potential to transform key sectors is evident. In water treatment,
these technologies allow the design of more efficient and sustainable adsorbents, promoting
advanced solutions for environmental remediation.
The adaptive neuro-fuzzy inference system (ANFIS) is a methodology that associates
the main characteristics of the fuzzy inference system (FIS) and the adaptive neural net-
work; this incorporates the properties of fuzzy systems to explain the uncertainty and
computational strength of neural networks. In the recent literature, reports exist including
this methodology. For removing Congo Red dye by adsorption, employing green poly
(amino amide) nanoparticles based on cellulose nanoparticles (Cell-PAMNs) [
127
]. The
ANFIS model was used to predict the removal percent of dye, achieving excellent precision
model data against experimental results using a mean square error (MSE) with a result of
4.49895
×
10
−5
. Another example is the modeling of the mechanical properties of silica
fume-based green concrete, achieving an R2value of 0.913 for the correlation of predicted
values with the target values [
128
]. Three-dimensionally printed green composites were
optimized, obtaining an average percentage error of less than 4.4
×
10
−2
% for experimental
and predicted data [
129
]. Recent work shows their performance in cellulosic fibers for
better green composites using an ANFIS structure of five layers, achieving an R
2
value
of 0.992 for two Young’s modulus and ultimate tensile strength prediction models [
130
].
Green concrete with partial replacement ANFIS modeling demonstrates a high accuracy R
2
value of 0.974 and discovered that the mixture of volcanic pumice (VP) with micro-silica has
the highest effect on the resistance of concrete [
131
]. Two major disadvantages of ANFIS
modeling are inoperancy in adjusting membership function parameters [
132
] and poor
decoding for black box representations [
133
]. For this reason, this specific technique is not
used extensively.
It is important to show that these techniques, the MSR, RNA, IA and ANFIS models,
have their advantages and disadvantages, which generates the use of techniques to model
and optimize systems based on green synthesis, thus achieving statistical analysis, such
as ANOVA and graphical representations, and obtaining mathematical equations and the
optimization of operating parameters. The use and combination of computational tools
with experimental validations and efforts to overcome technical challenges, such as data
quality and computational complexity, promise to accelerate the transition towards a more
sustainable and efficient material design [118].
Processes 2025,13, 566 20 of 29
7. Economic Aspects and Sustainability
Currently, a wide variety of traditional treatment methods are used to remove contam-
inants in different types of water [
134
]. These methods can be primary such as coagulation,
flocculation, sieving, separation and centrifugation. Secondary methods cover aerobic and
anaerobic processes. Also, tertiary methods have been used, among which evaporation,
oxidation, ion exchange, distillation, reverse osmosis and adsorption stand out. Likewise,
nanometric methods such as photocatalysis, nano-filtration, nanocomposites and nano
adsorbents have been used [
135
,
136
]. Most of these methods used conventional materials
derived from synthetic polymers with the objective of eliminating or reducing contaminants
present in water. However, these materials do not always prove to be effective, reinforcing
the need to explore more promising options.
Generally, most conventional methods used in wastewater treatments present signif-
icant challenges, particularly in terms of cost and sustainability [
137
]. These procedures
often involve considerable investments in operation and maintenance. In addition, there
is the fact that there is an intensive use of chemicals, which raises concerns about sustain-
ability and environmental risks. In this sense, compared to advanced green methods, there
are several notable disadvantages such as high energy consumption, high temperatures
and pressures, the inadequate removal of contaminants, high operating expenses and the
formation of toxic byproducts. These are critical aspects that require attention and that
limit the long-term economic viability of conventional methods, especially in a global
context that prioritizes a reduction in energy consumption and the mitigation of climate
change [37,135].
In general, products based on advanced green materials are derived from renew-
able and sustainable sources; they are called advanced materials because their physical,
chemical, optical, electrical and biological properties improve their performance on a large
scale [
138
] and are classified due to the source of raw materials used in their preparation,
their development process and their interaction with the environment [
139
]. In this sense,
advanced green materials emerge as a promising alternative and are becoming increasingly
relevant in the field of water treatment [
140
]. Agricultural byproducts have been used as
advanced green materials for efficient water treatment and remediation and the removal of
heavy metals in wastewater [
141
]. Among which are natural polymers [
37
,
45
,
142
], which
have recently been modified to develop biomaterials and nanomaterials [
140
]. Numerous
studies have been carried out to develop efficient methods of water treatment and remedia-
tion through the synthesis of various materials from green biomass. For example, wheat
straw [
143
] and aloe vera [
144
], as well as wheat and rice straw [
145
], have been used.
In addition, non-membranous materials, such as algae and activated carbon, have been
used [
146
]. In addition, natural polymers have been explored, including cellulose, starch,
lignin, chitosan and alginates [
37
,
45
–
47
]. All of these ecological and sustainable materials
contribute to the sixth Sustainable Development Goal (SDG) established in the 2030 Agenda
by the United Nations, which seeks to guarantee access to clean water and sanitation. In
addition, they favor other SDGs related to health, the economy and the environment.
Regarding the cost and effectiveness, some research suggests that the use of green
materials at nanometer scales can make wastewater treatment more energy efficient; this
is due to the structural qualities of nanomaterials, such as porosity and active sites [
85
].
They also have high specificity and adsorption capacity for toxic substances or other
contaminants due to their high surface area [
140
,
147
,
148
]. However, the use of advanced
green materials requires a higher dosage to achieve the desired effectiveness. In addition,
its implementation involves a more rigorous preparation process and adequate storage. It
is also important to consider that the availability of these materials may be seasonal, which
limits their use throughout the year [142].
Processes 2025,13, 566 21 of 29
The use of green materials for wastewater treatment presents various challenges,
especially related to existing infrastructure and technologies [
21
]. Although many of
these materials and biomaterials show promising performance in controlled laboratory
environments, the ability to maintain their stability and efficiency at pilot scales and
under field conditions remains a significant challenge. This situation represents a crucial
research gap that must be addressed through continued studies with high-performance,
low-cost technologies. Additionally, it is essential to consider the life cycle and long-term
performance of ecological materials as these factors significantly influence their commercial
viability at an industrial level. Therefore, it is crucial to conduct additional research that
delves into these aspects, with the aim of optimizing the acceptance and use of these
materials in the market.
In the current context, where concern about climate change and environmental degra-
dation intensifies, it is crucial that the research and development of materials for water
treatment focus on innovative technologies that competitively address these challenges.
This involves effectively integrating advanced green materials and biopolymers, thus pro-
moting a transition towards sustainability in the modern economy. Such a transition is
essential to mitigate the environmental impacts associated with the use of conventional
materials, allowing a sustainable balance to be achieved between economic growth and
the conservation of natural resources. Although there are currently no studies that offer
a clear cost–benefit analysis of the use of advanced green materials in water treatment,
the literature does highlight the advantages and properties of these compounds. Among
these properties are its biodegradability, high polarity, barrier characteristics and excellent
mechanical properties. These positive effects reinforce the attractiveness of green materials
in the context of a holistic approach to resource management, positioning them as an
economically viable option. Undoubtedly, the development and implementation of ad-
vanced green materials require considerable investment; however, the long-term economic
benefits outweigh the costs. This is especially relevant when considering the importance of
sustainable water management for human development, as well as for mitigating health
problems and environmental impacts.
8. Challenges and Future Perspectives of Green Materials
Conventional technologies currently used in water and wastewater treatment have
several limitations, highlighting the need to investigate more advanced approaches. In
this sense, nanotechnology emerges as an innovative and highly efficient method for the
synthesis of materials that are more environmentally friendly [
135
,
137
]. This technology
allows obtaining materials with exceptional mechanical properties and thermal stability
in addition to reducing dependence on large infrastructures [
134
,
147
,
149
]. According to
Thangavelu and Veeraragavan (2022), nanotechnology is establishing itself as a growing
industry, integrating with the conventional methods most used in wastewater treatment. At
the nanometer scale, materials have a wide variety of applications thanks to their reactivity
and specific surface area characteristics. However, research conducted by Paul et al. (2024)
and Magalhães-Ghiotto et al. (2021) indicated that the synthesis of green nanomaterials can
be affected by various factors, including biological sources, pH, temperature and surface
charge. In this context, Rathod et al. (2024) highlighted that the use of green materials faces
important challenges, such as technical and financial obstacles, as well as the need to carry
out studies on the life cycle of the products. Likewise, Dokania et al. (2025) emphasized
that the synthesis of nanomaterials is a process that requires considerable time and, due
to the slower methods used, can be expensive, which represents a significant limitation
especially when addressing large-scale wastewater treatment [
45
,
135
,
140
,
149
,
150
]. Finally,
Kumari et al. (2023) mentioned that green nanotechnology-based materials can be produced
Processes 2025,13, 566 22 of 29
efficiently, but the pre-processing of those products is where the biggest safety concerns lie.
Although only a few have reached the market, advanced green materials play a vital role
when competing with conventional technologies, and, in the coming years, the practical
usefulness of nanobiotechnology for expansion and commercial viability in wastewater
treatment industries will be very important [140].
To overcome the above disadvantages, further research should be carried out that
includes the synthesis of green materials in a safer way, designed with an improved
structure and surface properties. In addition, these methods are required to be highly
selective, more efficient, easy to operate and, therefore, profitable. This area still lacks
studies that compare its potential with respect to conventional materials [
140
,
151
]. Another
important point is the use of AI in the design and optimization of green materials applied
to water treatment. This represents a paradigm shift in the synthesis of green materials,
offering significant advantages in efficiency and exploration capacity. However, it faces
technical limitations that must be overcome, such as data quality and the experimental
validation of predictions. As these tools mature and are integrated with other methods,
their potential to solve environmental and energy problems will be even greater.
Despite continued efforts to develop efficient, low-cost materials for water treatment,
the need remains to create smart, adaptable porous surfaces that enable effective wastewa-
ter treatment. Current trends are oriented towards the use of materials whose production
minimizes energy consumption. Without a doubt, the future is oriented towards technolo-
gies that integrate nanometric materials based on biomass, bioadsorption, biodegradation
and nanoparticles synthesized in an ecological way. However, the global economy will
depend largely on our ability to innovate and adapt to a more sustainable model. Research
in advanced ecological materials and biopolymers is super important, not only in the
scientific environment, but it is also a commitment to future generations. By prioritizing
sustainability in our economic and technological decisions, we can contribute to a more
balanced and healthier world where human development and environmental preservation
go hand in hand. This could lead to new ways of producing ecological materials for better
performance in separating contaminated water.
9. Conclusions
The development of advanced green materials has proven to be a fundamental tool
to address global challenges in water and wastewater treatment, especially in the face of
problems such as emerging pollution and the scarcity of water resources. These materials,
characterized by their biodegradability, renewable origin and low toxicity, offer a sustain-
able alternative to conventional materials, reducing environmental impacts and promoting
a circular economy. The integration of naturally occurring nanomaterials, biopolymers and
hybrid composites has optimized the adsorption capacity, contaminant removal efficiency
and durability of the proposed solutions. Likewise, modeling and optimization using
different computational techniques are emerging innovative tools that accelerate the design
and optimization of these green materials, allowing one to predict properties, simulate
interactions and customize solutions according to the specific characteristics of the treated
water. However, progress towards a massive implementation of these materials faces
technical, economic and scalability challenges, including the dependence on high-quality
data, the costs associated with synthesis and limitations in experimental validation.
Author Contributions: Conceptualization, B.S.-R.; formal analysis, H.P.H. and J.P.M.R.; investigation,
H.P.H., J.P.M.R., C.L.R.-C. and J.F.-G.; writing—original draft preparation, C.L.R.-C. and J.F.-G.;
writing—review and editing, B.S.-R.; supervision, B.S.-R. All authors have read and agreed to the
published version of the manuscript.
Processes 2025,13, 566 23 of 29
Funding: This research received no external funding.
Data Availability Statement: No new data were created or analyzed in this study.
Conflicts of Interest: The authors declare no conflicts of interest.
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