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Development of chitosan/ Spirulina bio-blend films and its biosorption potential for dyes
Journal of Applied Polymer Science
Abstract and Figures
Chitosan/Spirulina bio-blends (CSBB) in films form were developed to be an alternative/renewable biosorbent, able to remove anionic and cationic dyes from aqueous solutions. CSBB potential as biosorbent was investigated for cationic dye Methylene Blue (MB), and anionic dyes Tartrazine Yellow (TY) and Reactive Black 5 (RB5). Chitosan and Spirulina samples were obtained and characterized, and CSBB films were prepared with different chitosan/Spirulina ratios. The CSBB films characteristics, as, mechanical properties, thermal profile, crystallinity, functional groups, morphology, and biosorption potential were strongly dependent of chitosan/
Spirulina ratio. CSBB films preserved its mechanical structures at pH from 4.0 to 8.0. The biosorption capacities were 120, 110, and 100 mg g-1 for RB5, TY, and MB, respectively. The increase of chitosan amount favored the TY and RB5 biosorption; however, the increase of Spirulina amount favored the MB biosorption. Thus, the CSBB in film form is a renewable biosorbent suitable to remove anionic and cationic dyes from aqueous solutions.
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... The peaks observed at 1534 cm −1 , and 1448 cm −1 can belong to the bendings of NH 2 , CH 2 respectively and at 1396 cm −1 to the stretching of C-H, -CH 2 , and -CH 3 groups (Sargin et al., 2016). The band at 1019 cm −1 was attributed to -P-O symmetric and asymmetric stretching vibrations relative to the phospholipids present in the Spirulina and the presence of -C-O groups of cellulosic structures (Khan et al., 2012;Rahmi et al., 2017;Sargin et al., 2016;Silva et al., 2017). Figure 1b indicates the FTIR peaks of Perna canaliculus. ...
... The peak at 1396 cm −1 was attributed to CH 3 CO stretching. The bands in the range of 1150 and 1023 cm −1 showed the C-O-C and C-O stretching in the biopolymer chain (Silva et al., 2017). FTIR spectrum of SPC (Fig. 1c) involved the combination of peaks that occurred in the spectras of Spirulina and Perna canaliculus. ...
... FTIR spectrum of SPC (Fig. 1c) involved the combination of peaks that occurred in the spectras of Spirulina and Perna canaliculus. The shift of wave number of 1638 cm −1 on the Spirulina into 1638 cm −1 on the SPC proved the hydrogen bonds formed between the constituents of the composite and it was seen that the intensity of the peaks at 1637 cm −1 related to the C = O groups and 1519 cm −1 belonged to NH 2 bendings of protein that is highly available in Spirulina increased when Spirulina used as organic filler in Perna canaliculus (Khan et al., 2012;Silva et al., 2017). Figure 1d shows the spectrum of RB5 dye-loaded biocomposite (SPC). ...
In this study, Reactive Black 5 (RB5) removal potential was investigated by Spirulina and Perna canaliculus biocomposite (SPC) in batch and continuous systems. FTIR, Point of Zero Charge, and SEM analyzes were performed to elucidate the structure of the biocomposite. In the batch system, the effects of pH, biosorbent dose, contact time, temperature, and initial RB5 concentration on the biosorption process were investigated. The flow rate and bed height studies were carried out in the continuous system. Langmuir, Freundlich, and Scatchard isotherm models were used to describe the biosorption process. The experimental data fitted best to the Langmuir isotherm model, and the maximum monolayer biosorption capacity was determined as 277.6 mg/g. In kinetic studies, pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were applied, and it was determined that the process followed the pseudo-second-order kinetic model. Equilibrium was established in 30 min for RB5 removal with SPC biocomposite. As a result of the studies carried out in the continuous system, the biosorption efficiency was higher at the low flow rate and increased with the rising bed height. In biosorption-desorption cycle studies, RB5 removal by SPC was successful for up to 10 cycles. Also, the biosorption process was applied to simulated wastewater and the results indicated that the biosorption capacity was not affected significantly by the existence of many other metallic and organic pollutants. As a result of the findings, it was concluded that SPC could be an effective and alternative biosorbent in RB5 removal.
... Besides all these findings, the macromolecules variety that makes Spirulina sp. can be combined with other biomaterials to form cohesive and firm matrices, such as bioblends of chitosan and Spirulina sp. (Silva et al. 2017). Chitosan is a natural polymer that has high commercial value and interesting properties in the industrial and research fields, being that an expressive number of publications were related the chitosan modification and application as adsorbent in wastewater treatment (Brion-Roby et al. 2018;Hossini et al. 2017;Ignat et al. 2016). ...
... Moreover, bioblends are systems that originated from the physical mixture of two or more components, whose main objective is to incorporate the properties of the different compounds into the same material. Silva et al. 2017 developed bioblends films of chitosan/Spirulina sp., for application in the dyes removal from aqueous solutions; the authors observed that the films of the bioblends preserved its mechanical structures at pH ranges from 4.0 to 8.0, and they found that the bioblends films of chitosan /Spirulina sp. were suitable for removing anionic and cationic dyes from aqueous solutions. ...
... Thus, for the application Spirulina sp. and chitosan as adsorbent in fixed bed column is required its structural modification to improve particle characteristics necessary by system hydrodynamics (Auta and Hameed 2014;Gokhale et al. 2009). Among the techniques applied for the structural modification there is the casting technique, which is used for chitosan films production (Moura et al. 2015) and bioblends of Spirulina sp./chitosan (Silva et al. 2017). ...
The glass particles were coated with Spirulina sp. LEB-18 and bioblends of Spirulina sp. LEB-18/chitosan by casting technique and, afterward, it was verified its potential as adsorbents for basic and acid dyes. Nine Spirulina sp. suspensions with different components were used to coat the glass particles, and in the best condition of coating were prepared the bioblends with chitosan. The coated glass particles with Spirulina sp. and its bioblends with chitosan were applied in adsorption of the allura red (acid) and methylene blue (basic) dyes in a batch operation evaluate the pH effect, and a fixed bed column operation, being evaluated to the removal percentage and adsorption capacity of the column. The glass particles coated with Spirulina sp. applied in batch adsorption showed the highest removal percentages for allura red dye (35 to 45%) at pH 4.0, and for methylene blue dye (35 to 80%) at pH 6.0 and 8.0. In fixed bed column using glass particles coated with bioblends were reached the amount dye of 54.2 mg of adsorbed allura red dye and 60.2 mg of the of adsorbed methylene blue dye, respectively. Moreover, it was found good dye adsorption capacities, around 89 mg g−1, for both dyes, in acidic and basic pH values. Based on these results, these bioblends coated glass particles can be applied as an adsorbent for different types of dyes in adsorption column.
... At the end of cultivation, the biomass was recovered by filtration, washed with distilled water and pressed to recover the biomass with a moisture content of 76.0% (wet basis). The wet biomass was dried at 60°C by a perforated tray drier with perpendicular air flow according to previous works [18,19] and sieved until the particle size of 68 ± 6 μm. ...
... After complete dissolution of chitosan, Spirulina sp. (30% wt) was added and it was stirred at 25,000 rpm on a mechanical stirrer (Bosch GS 927 Professional, Brazil) at ambient temperature (25°C) for 10 min [18]. Then, glutaraldehyde (1.5% (v/v)) was added to form a hydrogel. ...
A new adsorbent composed with Spirulina and chitosan was developed to phenol removal from aqueous solution. The material was synthesized to obtain a hybrid foam, and then it was characterized by scanning electron microscopy (SEM), infrared spectrum (FT-IR), thermogravimetric analysis (TGA) and Bennett, Emmet and Teller (BET) method. Isotherms were performed in different temperatures and thermodynamic parameters were estimated. Kinetics behavior was evaluated using different stirring rates (50, 100 and 150 rpm) and was adjusted to different kinetic models. The results show the adsorbent presented a rough and irregular surface, which indicates good accessibility to phenol onto an adsorbent surface, a specific surface area of 1112 m² g⁻¹ and pore sizes from 45 to 140 μm. Dubinin-Radushkevich isotherm was the most appropriated to represent the equilibrium data and the maximum adsorption capacity was 447.6 mg g⁻¹. Thermodynamics parameters indicated that the adsorption was exothermic. Pseudo-first-order kinetic model was the most adequate to represent the adsorption phenomenon at all rotations.
... Based on the above viewpoints, biosorption is the most eco-friendly technique to remediate dye contaminants in an efficient manner (Sharma et al. 2018). Many types of research have recognized bacteria and algae as well as fungi Responsible editor: Guilherme L. Dotto (yeast) and their biomass as excellent biosorbents (Cid et al. 2015;Deng et al. 2006;Dotto et al. 2015;Silva et al. 2017a). Among these, bacteria are extensively studied for biosorption because of their abundant availability, ubiquitous nature, and low cost. ...
... Therefore, the maximum adsorption capacity was expected to be greater than 91 mg g −1 . Similar results were obtained for the adsorption of MB on activated carbon surfaces, cane bark powder, and Chitosan/ Spirulina bio-blend films used as adsorbent (Enenebeaku et al. 2017;Santhi and Manonmani 2009;Silva et al. 2017a). ...
A nano-biosorbent for the removal of methylene blue (MB) was prepared by encapsulating iron oxide nanoparticles (NPs) and Agrobacterium fabrum strain SLAJ731, in calcium alginate. The prepared biosorbent was optimized for the maximum adsorption capacity at pH 11, 160 rpm, and 25 °C. Adsorption kinetics was examined using pseudo-first-order, pseudo-second-order, and intra-particle diffusion (IPD) models. The kinetic data agreed to pseudo-second-order model indicating chemisorption of MB, which was also explained by FTIR analysis. The adsorption rate constant (k2) decreased and initial adsorption rate (h, mg g⁻¹ min⁻¹) increased, with an increase in initial dye concentration. The dye adsorption process included both IPD and surface adsorption, where IPD was found to be a rate-limiting step after 60 min of adsorption. The adsorption capacity was found to be 91 mg g⁻¹ at 200 mg L⁻¹ dye concentration. Adsorption data fitted well to Freundlich isotherm; however, it did not fit to Langmuir isotherm, indicating adsorbent surfaces were not completely saturated (monolayer formed) up to the concentration of 200 mg L⁻¹ of MB. Thermodynamic studies proposed that the adsorption process was spontaneous and exothermic in nature. Biosorbent showed no significant decrease in adsorption capacity even after four consecutive cycles. The present study demonstrated dead biomass along with NPs as a potential biosorbent for the treatment of toxic industrial effluents.
... This may be due to the adhesion of dyes as a single layer on the outer surface of the adsorbent [61,62]. Subsequently, due to the scarcity of active sites present on the outer surface of ZDHs, the dyes cause slow diffusion and slow adsorption towards the inner surface of the hydrogel beads [63,64]. However, in terms of time feasibility, it is suggested that 60 min will be sufficient to reach the maximum Similarly, in a study in which the Congo red dye was removed by adsorption using PVA/GA (Polyvinyl alcohol/Glutaraldehyde) hydrogels, it was found that dye uptake by the hydrogel beads was rapid for the first 100 min and then proceeded at a slower rate before reaching equilibrium [20]. ...
This study aims to determine the synthesis of zeolite-based hydrogel composites and their decolorization potential by adsorption method from real textile wastewater containing dye mixture. Initial bridging was used to create the cross-linked hydrogel with polyvinyl alcohol (PVA) and sodium alginate (SA), and then natural zeolite (clinoptilolite) particles were uniformly distributed throughout the polymer matrix. Investigations were also conducted into the impacts of adsorption correlation parameters such as pH, adsorbent concentration, reaction time, temperature, zeolite (%) content and drying time (particle size) by using the Response Surface Methodology. SEM and FTIR techniques were used to analyze changes in the parental hydrogel polymer's property profile following the addition of zeolite. It was found that the adsorption process applied for color removal with Zeolite/PVA/SA hydrogel composite was a chemical process that could achieve 86% optimum color removal and 166 Pt–Co/g adsorption capacity, respectively. Adsorption kinetics was most effectively explained using a pseudo-second-order model, and the adsorption isotherm followed the Langmuir model with a 559.47 mg/g adsorption capacity. Intraparticle and liquid film diffusion mechanisms worked together to control the diffusion of dye molecules into the ZDH's internal structure. In addition, when the change in the performance of ZDHs after it was activated and applied five times was examined, it was determined that the activation did not have a significant effect on the reusability of the ZDH particles. When the same particles were subjected to color adsorption in wastewater five times in a row, the adsorption efficiency of ZDHs decreased significantly after the third application. It was also demonstrated that the ZDH particles did not desorb color in three consecutive cycles without the need for any activation. This study also revealed that zeolite doped hydrogel particles could be used as an alternative, environmentally friendly, low-cost adsorbents for color removal from industrial wastewater containing dyestuffs like those in the textile industry.
... In addition, these phenomena could also be attributed to the acidic solvent (acetic acid) used in the preparation of spinning solutions, which prevented the partial renaturation of gelatin from random coil to triple helix, that typically occurs during gelling from aqueous solutions (Panzavolta et al., 2011). Silva et al. (2017) prepared chitosan/Spirulina bio-blend films and found that the crystallinity of films decreased with increasing Spirulina content due to utterly amorphous structure of Spirulina biomass. The lower crystallinity of nanofibers is a beneficial characteristic when considering fast-dissolving applications as reported for menthol release from Balangu-gelatin nanofibers . ...
Spirulina is a microalga that is well-known for its high protein content and biological activities directly related to its antioxidant capacity. The objective of this study was to produce fast-dissolving antioxidant nanofibers based on Spirulina protein concentrate (SPC) and gelatin using needleless electrospinning technique. The effect of mixing ratios of SPC (10% w/w) and gelatin (20% w/w) on the viscosity, electrical conductivity and surface tension of electrospinning solutions as well as diameter and morphology of resulting nanofibers was investigated. Increasing the SPC level in the solution blends resulted in a decrease in apparent viscosity and electrical conductivity and an almost stable trend in surface tension (29.25–32.19 mN/m) that led to diminish of diameter of the nanofibers. Scanning electron microscopy images showed that SPC/gelatin ratio of 40:60 led to the production of uniform and bead-free nanofibers with a relatively smaller average diameter (208.7 ± 46.5 nm). Atomic force microscopy images indicated mesh-like, fibrillary, and bead-free structures. Fourier transform infrared spectroscopy verified the formation of composite nanofibers and intermolecular interactions between both proteins. X-ray diffraction and thermal analysis showed higher amorphous structure and stability of produced SPC/gelatin nanofibers in comparison to pure materials which was favorable for formation of stable fast-dissolving fibers. Results of DPPH and ABTS radical scavenging activities showed that the antioxidant activity of composite nanofibers significantly improved with increasing SPC mixing ratio (p < 0.05). The dissolution test demonstrated that SPC/gelatin nanofibers can be rapidly dissolved in aqueous medium within 2 s. Finally, the results indicated that the electrospun SPC/gelatin nanofibers could be potentially used for nutraceutical delivery in food and packaging applications under high humidity.
... It has been noticed that, there was a rapid removal rate in the beginning of MB adsorption process which was declined towards the end of the experiments. The previous behavior may be the resultant of the potential MB monolayer formation on the external adsorbent surface [79,80], causing slow adsorption due to the scarcity of the available active sites on the zeolite surfaces and slower diffusion range of the dye through its inner layers after the surface saturation has been achieved [82,83]. ...
Synthetic Zeolite mixture (ZM) containing Analcime (ANA), Wairakite (W), and Phillipsite (PHI) was produced by alkali activation of andesite rock (AR) under hydrothermal conditions of 1.0&3.0 M NaOH, 100 °C, and duration of 1–5 days. The main affecting parameters for ZM phase crystallization were alkalinity, solution chemistry, parent rock dissolution rate, and reaction duration. The low alkali concentration was advantageous for ANA formation, and the hetero cationic slurry environment containing sodium and calcium resulted in co-crystallization of ANA-W zeolite series in the same pot. High alkalinity unfavored ANA persistence but was more suitable for PHI domination. The FT-IR results confirmed the conversion of the precursor rock into zeolites, whereas the measured surface area indicated the enlargement of the BET of the rock from 2.62 into 91.4 m²/g after zeolitization. The rock and synthetic product were identified using the X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), specific surface area (BET), and the structural groups for AR and ZM were tested using the FT-IR technique. The phase internal structures and microanalysis are monitored by the Scanning Electron Microscopy- Energy Dispersive X-ray Spectroscopy (SEM-EDS). Zeta potential of samples was measured using a particle size analyzer. For economic aspect, ZM formed at low alkali content of 1.0 M NaOH, 100 °C, and 5 days was evaluated for methylene blue dye removal as a model of textile wastewater. The effect of pH, contact time, initial concentration and zeolite dose on adsorption has been investigated. Zeta potential measurements revealed that, the pH pzc was 1.9. The maximum sorption performance was found to be 95.7% at 10 pH within 240 min and 1.5 g/L zeolite dosage. Furthermore, the application of the zeolitic product on a synthetic simulated effluent composed of different dyes and salts implied a removal efficiency of 92.63%. The isothermal investigation of Langmuir and Freundlich models at different temperatures revealed that, MB adsorption using the formed zeolite was adapted to the Freundlich isotherm. The dye removal was matched with the pseudo-first kinetic model. Also, the high efficiencies in the removal of dye molecules through 5 consecutive cycles were demonstrated in the regeneration experiments.
... The studded methods for water purification including, filtration, chemical precipitation, ion exchange, oxidation, ozonation, electrolysis, reverse osmosis, coagulation/flocculation, adsorption, and biological treatment. Among these, some operations can be performed using new hybrid material been an attractive way to remove contaminants, in low concentration, from aqueous effluents due to its simplicity of design, high removal efficiency, ease of operation and availability (Barbosa et al. 2016;Zhang et al. 2017;Silva et al 2017;Guo et al. 2019). ...
The increase in the population and, consequently, in the industrial and agricultural production has led the planet to the depletion of natural resources and, in particular, water resources. Seeking to minimize this problem, some operations can be performed using new hybrid materials, being an attractive way to remove contaminants, in low concentration, from aqueous effluents. The development of nanomaterials has advanced and the use of nanostructures has been receiving the attention of researchers for its application in wastewater treatment. This chapter presents information regarding the applicability of magnetic nanofibers to remove contaminants from the water medium. Three-dimensional networks formed by nanofibers are nanoarchitectures with controlled characteristics and tunable physicochemical features, with particular interest for the development of novel and functional materials. Polymeric membranes containing high porosity, with nanochannels, have been presented as suitable templates for obtaining 3D magnetic nanofiber networks that present magnetic and magneto-transport characteristics. Firstly, some concepts about the electrospinning process to obtain general nanofibers, the aspects involved in the synthesis, the polymers used to produce nanofibers, and some applications are presented. The magnetic nanofiber aspects and different methodologies to produce this hybrid material are also presented. The main necessary analysis to characterize a magnetic nanofiber with regard to textural, morphological, thermal stability, and magnetic aspects are elucidated. In order to illustrate the characterization essays, some examples of the literature are shown. Finally, some applications of the magnetic nanofibers in the removal of contaminants from the water medium and the characteristics of the different processes, their operating conditions, and the results of the treatment are identified.
... where K F is the Freundlich isotherm constant (mg mg −1 ) (L mg −1 ) −1/n ) and 1/n is their heterogeneity factor. Adsorption kinetic models describe the rate of adsorbate adsorbed onto the adsorbent and controls the equilibrium time (Silva et al. 2017;Alves et al. 2019). Estimated Langmuir and Freundlich isotherm parameters are presented in Table 1. ...
Considering the serious health effects of fluoride contamination, an environment friendly bioadsorbent was derived from wattle humus for fluoride removal by conventional thermal activation process. Analytical characterizations revealed that heterogeneous morphological textured wattle humus enabled remarkable adsorption capacity. XPS analysis substantiated that fluoride had been successfully adsorbed on to the carbonized wattle humus surface through chemisorption. Fluoride adsorption efficiency was systematically rationalized via batch adsorption studies. Experiments were performed at different initial fluoride concentration and scrutinized the impact of contact time (10–120 min), adsorbent dosage (0.5–2.5 g), pH (2.0–9.0), and interfering co-existing ions (SO4²⁻, NO3⁻, Cl⁻, and HCO3⁻) on fluoride removal. Even at different adsorbate dosage (2–10 mg/L), 98% fluoride removal efficiency was achieved under pH > 6. The competitive anions do not interfere the wattle humus fluoride adsorption capacity. Moreover, the adsorption isotherms and kinetics studies inferred that monolayer and multilayer adsorption behavior by wattle humus leads to noticeable fluoride adsorption. Adsorbent regeneration test affirms that regenerated adsorbent found higher (>95%) fluoride removal efficiency even at five recycle runs.
Graphical abstract
... The quantity of SCCs adsorbed (q t ) was calculated by using Eq. (1): Silva et al. 2017;Wang et al. 2013). ...
Irradiated waste high-density polyethylene@Zn/ionic liquid novel composite well-fabricated via coacervation method was irradiated by gamma-irradiation and studied the effect of that radiation on the desulfurization process. The prepared composites were characterized by various analytical techniques as follows: X-ray diffraction (XRD), Fourier-Transform infrared (FT-IR), X-ray photoelectron spectrometer (XPS), scanning electron microscope (SEM), High Resolution Transmission Electron Microscopy (HRTEM), N2-adsorption-desorption isotherm, and thermal gravimetric analysis (TG/DTA). The adsorptive desulfurization process of benzothiophene (BT) and dibenzothiophene (DBT) which are harmful compounds in diesel model fuel was investigating using the irradiated and unirradiated composite. The results illustrated that the unirradiated and irradiated composites exhibit an adequate adsorption capacity reached (50–75 mg S/g) and (60–85 mg S/g) for BT and DBT, respectively. The adsorption process over the prepared adsorbents follows the pseudo-second-order kinetic models. The irradiated composite exhibited more adsorption capacity than the unirradiated one due to the radiation generated more surface area and created proton-bond donor sites in the composite surface, which increases the interaction between the surface and sulfur species. The adsorption capacity and adsorption percentage for irradiated and unirradiated composites towards (SCCs) were studied using response surface methodology based on the central composite design (CCD). The thermodynamic factors (∆H°, ∆G°, and ∆S°) reveal that these processes are endothermic adsorption processes. The irradiated PEt @Zn/IL was re-used without significant loss of adsorption activity. This novel irradiated PEt @Zn/IL is the first time used as an adsorbent with an advantage that includes its excellent adsorption capacity, which ensures the product will be efficient in a real process such as the petrochemical industry.
... The decrease in the oxygen transmission rate was due to the intermolecular interactions between the chitosan, MMT K10 and spirulina and it was already proved in the tensile strength calculation. The addition of MMT K10 and spirulina possibly tightened the chitosan chain interactions and as a result of the decrease in oxygen transmission [21]. From the obtained results, it was proved that the chitosan with spirulina improved the oxygen transmission rate. ...
It is enviable to develop an environment-friendly packaging material against petroleum-based polymers with enhanced functionality to satisfy sustainable development and to secure and extend the shelf life of food. In this work, biopolymer chitosan was mixed with montmorillonite (MMT K10) nanoclay and spirulina algae to produce a bio nanocomposite film with high strength and barrier properties. Spirulina and MMT K10 was initially incorporated into chitosan to fabricate the chitosan/MMT K10/spirulina bio nanocomposite and the intermolecular interactions between the chitosan, MMT K10 and spirulina was improved by the synergistic effect of covalent and hydrogen bonds. The surface colour and opacity of chitosan bio nanocomposite films were found to be increased by the inclusion of MMT K10 and spirulina. The bio nanocomposite films exhibited good solubility and swelling property. The chitosan bio nanocomposite film with 0.5 g of spirulina revealed the promising features such as high tensile strength of 46.3 MPa, low oxygen and watervapour transmission rate of 996.79 cc/(m2. day.atm) and 7.12 g/m2/day which was better than other various concentration of spirulina based films. Furthermore, the antimicrobial properties of bio nanocomposite films were determined by colony count method and the results suggested the films had excellent antimicrobial properties against both gram-positive and gram-negative microorganisms and the composite films showed the good biodegradable property. The fabricated chitosan-based MMT K10 and spirulina incorporated bio nanocomposite films could make valuable contributions in active food packaging applications due to its excellent properties.
... From the results observed, it could be inferred that maximum removal of the As 5+ , Cr 6+ , and Cd 2+ ions by the biosorbent took place at nearly neutral pH, whereas with an increase in pH, the removal percentage of the metal contaminants gets decreased. This may be due to an increase in pH the surface of the biosorbent get deprotonated; this H + ions increase prevents the formation of bonds between the adsorbate surface and trace metal ions (Silva et al. 2017;Nakkeeran et al. 2016;. Thus, it could be considered that this biosorbent has maximum biosorption capacity for various metal contaminants at nearly neutral pH level. ...
Biosorption is an ingenious technique that uses biological materials to acquire trace metal ions from wastewater. In the present study, the ability of Colocasia esculenta stem biomass was explored for the biosorption of toxic trace metals. The maximum removal was observed for arsenate (As⁵⁺) with 58.63%, followed by chromium (Cr⁶⁺) with 56.56%, and cadmium (Cd²⁺) with 41.2%. However, for copper (Cu²⁺), nickel (Ni²⁺), and zinc (Zn²⁺), low adsorption was observed. Batch sorption tests revealed that adsorbent dosage of 0.5g, 0.5g, and 0.3g; time of 10 h, 4 h, and 10 h; room temperature range of 25–30°C; pH range of 7.0–4.5; and initial concentration of 30 μg/L, 20 mg/L, and 30 mg/L were the optimum conditions for the removal of As⁵⁺, Cr⁶⁺, and Cd²⁺, respectively. Scanning electron microscope and energy-dispersive X-ray spectroscopy (SEM-EDX) analysis of Colocasia esculenta stem biomass before and after adsorption revealed that the trace metals successfully get adsorbed on the surface of the biosorbent. The equilibrium data fitted well with the adsorption isotherm model of Langmuir (for As⁵⁺, Cr⁶⁺, and Cd²⁺), Dubinin-Radushkevich (for As⁵⁺ and Cr⁶⁺), and Flory-Huggins (for Cd²⁺), and the kinetic data of As⁵⁺, Cr⁶⁺, and Cd²⁺ biosorption were best described by pseudo-second-order kinetic model. Thermodynamic studies revealed that the adsorption process for all concerned trace metals acts in a spontaneous manner and is endothermic in nature. Thus, the use of Colocasia esculenta stem biomass proved to be an efficient and economical alternative for the treatment of effluents contaminated with these trace metals.
... The results showed that the adsorption process was controlled by chemisorption, and chemical bonds were formed by electron transfer or electron sharing between the adsorbent and the adsorbate. Therefore, the interaction between these heavy metal ions and functional groups was the key adsorption power (Cao et al. 2019;Huang et al. 2018;Sharma et al. 2018;Silva et al. 2017). ...
In this paper, three-dimensional magnetic nitrogen-doped porous carbon modified by EDTA (N-MPC-EDTA) was successfully prepared by two-step method with lignin as the precursor, and was used for the removal of Cd (II). The 3D adsorbents were characterized by SEM, TEM, BET, XRD, XPS, Zeta potential, and element mapping analysis techniques, and the performance of the materials was tested by the batch adsorption method. The influence of experimental parameters such as contact time and pH value on the adsorption capacity of N-MPC-EDTA on Cd (II) was studied. Under the optimal conditions, the equilibrium adsorption capacity of Cd (II) was 43.68 mg∙ L⁻¹ and the adsorption equilibrium was quickly reached within 45 min. A possible adsorption mechanism was proposed, in which the chelation of EDTA as well as the electrostatic attraction of hydroxyl, carboxyl, and nitrogen-containing functional groups dominated the adsorption of Cd (II). The adsorption kinetics and isotherm data fitted well with the pseudo-second-order kinetic model and Freundlich model, respectively. In addition, the good regeneration performance suggested that N-MPC-EDTA will have a broad application prospect in water treatment.
Graphical abstract
... In these processes, copper exists as compounds or in the metallic form which can solubilize and is released in water as sludge waste containing copper (II) ions which inevitably accumulates in drinking water where it is toxic even at low concentrations [8]. Classical wastewater treatment techniques such as evaporation, solvent extraction, chemical precipitation etc. [9] are being abandoned in favour of more advanced technologies such as phytoremediation, bioremediation, microbial remediation, and adsorption [10,11]. Adsorption technology is based on the deposition of pollutant mass on the surface of a solid [12]. ...
In the present work, raw waste material obtained from polluting dried tree fibres (raw TF) as a source of natural carbon was used for the removal of contaminating copper ions in water. Through two sequential steps of oxidation, carbonaceous adsorbent materials were obtained. Namely, tree fibre activated carbon treated with sulphuric acid (TFSA) and oxidised activated carbon modified using Hummer's method (TFHM). These materials were then characterized using techniques such as SEM, TEM, XRD, FTIR, XPS, TGA, Raman, and BET. The surface areas were found to have an increase from 0, 0.3109 and 55.0107m²/g for raw TF, TFSA, and TFHM, respectively. The carbonaceous adsorbents were then used in batch adsorption studies for the removal of copper ions in a test water solution. The maximum adsorption capacities determined by non-linear estimation models at the optimum pH 6, were 11.04 and 80.19 mg/g for TFSA and TFHM, respectively. Furthermore, copper is known to facilitate many organic transformations such as reduction and cyclisation, thus, the spent carbonaceous adsorbents were re-used in cyclocondensation and catalytic reduction reactions to avoid discarding these into the environment and creating secondary pollutants. The initial catalytic studies of cyclocondensation of benzamine lead to 96 and 98% yield of desired product via recrystallisation while catalytic reduction of 4-nitrophenol was obtained 92% within 22 min.
... It has a preferable binding tendency towards anionic water pollutants due to the availability of protonated amino (-NH 3 + ) functional groups which are responsible for adsorbing an anionic organic molecule especially in acidic environments by electrostatic attraction (Adnan et al., 2020). Many studies have reported the application of CS and CS derivatives for the removal of pollutants from water/wastewater such as congo red and methyl orange (Li et al., 2018), tetracycline (Zhao et al., 2020), Tartrazine Yellow and Reactive Black 5 Silva et al. (2017),(and phenol (Alves et al., 2019). ...
In this work, Schiff's base magnetic crosslinked chitosan-glyoxal/Fe3O4 composite (CS-G/Fe3O4) was synthesized and further developed by loading zinc oxide (ZnO) nanoparticles into its polymeric matrix. The final composite material of magnetic crosslinked chitosan-glyoxal/ZnO/Fe3O4 nanoparticles (CS-G/ZnO/Fe3O4 NPs) was tested for the removal of organic dye pollutant (reactive blue 19, RB19). The synthesized magnetic nanomaterials were characterized by several techniques such as CHN elemental analysis, Brunauer-Emmett-Teller analysis, vibrating-sample magnetometer, X–ray powder diffractometry, Fourier Transforms infrared, scanning electron microscope, energy dispersive X-Ray analysis, pHpzc, and pH-potentiometric titrations. A statistical approach namely Box–Behnken design (BBD) was applied to optimize the synthesis conditions as well as adsorption key parameters (A: ZnO nanoparticles loading (0–50%), B: adsorbent dosage (0.02–0.1 g), C: pH (4–10), D: temperature (30–60 °C), and time E: (10–60 min)). The adsorption kinetic and equilibrium results were well described with pseudo-second order model and Freundlich isotherm model, respectively. The maximum adsorption capacity of CS-G/ZnO/Fe3O4 NPs for RB19 was 363.3 mg/g at 60 °C. The adsorption mechanism of RB19 onto CS-G/ZnO/Fe3O4 NPs can be ascribed to several types of interactions (e.g. electrostatic attractions, hydrogen bonding, and n-π interactions). This study provides a new and effective adsorbent for water remediation due to its recoverability and high efficiency in removing the organic dye pollutants.
... The mobile phase was a mixed solution of methanol-water-acid (57: 43:0.001, v:v:v) with the flow rate of 1.0 mL min −1 at 30°C, and the adsorption capacity Q e of TYL on MIP and NIP was calculated based on equation Q e = 1000(C i − C e )V/m (Silva et al. 2016;Zhu et al. 2019). The adsorption kinetics of polymers was carried out according to the equilibrium adsorption experiment at the concentration of 25 mg L −1 at 25°C, 35°C, 45°C, and 55°C, respectively, and binding amount was calculated at different time intervals in 5-480 min by the equation Qt = 1000(Ci − Ct)V/m (Alves et al. 2019). ...
A novel eco-friendly molecularly imprinted polymer (MIP) was proposed as solid-phase extraction (SPE) adsorbent to selective adsorption tylosin (TYL) in animal muscle samples. The MIP was synthesized in aqueous by using 1,4-butanediyl-3,3-bis-1-vinyl imidazolium chloride and 2-acrylamide-2-methylpropanesulfonic acid as bifunctional monomer. The obtained MIP had excellent selectivity towards TYL in water, and the maximum binding capacity can reach 123.45 mg g⁻¹. Combined with high-performance liquid chromatography, the presented MIP can be used as SPE sorbent to recognize and detect TYL in the range of 0.008 to 0.6 mg L⁻¹ (R² = 0.9995). The limit of detection and limit of quantification were 0.003 mg L⁻¹ and 0.008 mg L⁻¹, and the intraday and interday precision were 1.05% and 3.36%, respectively. Under the optimal condition, the established MIP-SPE-HPLC method was successfully applied to separate and determine trace TYL in chicken, pork, and beef samples with satisfactory recoveries ranged from 94.0 to 106.3%, and the MIP-SPE cartridge can be cycled at least 20 times. This study implies a promising green MIP-SPE-HPLC method for highly selective adsorption and analysis trace TYL in complex matrices.
... It is possible to observe that the QPP sample presents a wide variety of functional groups compared to QPPAC. The strong band around 3414 cm − 1 present in both materials corresponds to the N-H or O-H stretching vibration [33] The 2922 cm − 1 and 2958 cm − 1 bands present only in the QPP sample are related to the C-H stretching vibrations in the methyl group [34]. The band in the 1749 cm − 1 region present in the QPP sample may be attributed to the C˭O bond present in ketones [35]. ...
In this work, an activated carbon sample with a high adsorptive performance for the herbicide 2,4-dichlorophe-noxyacetic acid (2,4-D) was prepared from queen palm endocarp (Syagrus romanzoffiana) by pyrolysis process. The activated carbon presented an XRD pattern related to carbon graphite and functional groups such as C-H, C˭O, O-H. The material particles presented a highly-porous structure, being beneficial to the adsorption process. The activated carbon showed a remarkable specific surface area of 782 m 2 g − 1 and pore volume of 0.441 cm 3 g − 1. The solution pH presented a strong influence on the adsorption process, with ideal pH = 2, being the best adsorbent dosage, 0.5 g L − 1. The correspondent removal percentage was 95.4%. The pseudo-second-order model represented kinetic data, presenting R 2 > 0.992 and MSR< 19.62 (mg g − 1) 2. The Langmuir model was the most suitable for describing the equilibrium data with the highest R 2 (> 0.997) and lowest values of MSR (< 92.04 (mg g − 1) 2), indicating a maximum capacity of 367.77 mg g − 1. The thermodynamic study indicated a spontaneous operation, with ΔG 0 ranging from-23.2 to − 32.6 kJ mol − 1 and endothermic process (ΔH 0 = 67.30 kJ mol − 1), involving physical interactions in the adsorbent/adsorbate system. The adsorbent could be regenerated by NaOH and used 7 times with the same adsorption capacity. Hence, overall, the activated carbon prepared from the Jerivá endocarp corresponds to a promising adsorbent in removing 2,4-D herbicide in wastewater.
... At present, there are various techniques which are applied for removal of these azo dyes such as ultrafiltration (Bouazizi et al. 2017), coagulation (Shi et al. 2007), photodegradation (Hachem et al. 2001) and reverse osmosis (Al-Bastaki 2004). Adsorption is one of the most effective techniques which is employed by various industries for the treatment of wastewater in order to reduce the pollutants present in it (Jain and Sikarwar 2006, Lütke et al. 2019, Silva et al. 2016. Adsorption can be performed using membrane filtration, electrochemical method, modified clays and organic sorbents etc. (Kausar et al. 2018;Brillas and Martínez-Huitle 2015;Zare et al. 2018). ...
The leaf extract of Ficus retusa plant was used for fabrication of α-MnO2 nanoparticles (NPs). The extract was utilized as a reducing agent for green synthesis of nanomaterial. The synthesis of nanocrystals was confirmed using different analytical techniques such as field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) spectroscopy and thermogravimetric analysis (TGA). The synthesis of NPs was studied over a wide range of temperatures from 80 to 800 °C. It was found that perfectly crystalline α-MnO2 NPs were successfully synthesized at 800 °C. The synthesized NPs were applied as an adsorbent for adsorption of azo dyes such as methyl red (MR) and methyl orange (MO) which are released as wastes from industries into water bodies and pollute the water. The removal efficiency was analysed and optimized depending on various parameters like pH, concentration of NPs, and contact time. The experimental data was explained by three isotherm models, viz. Langmuir, Freundlich and Temkin isotherms. Kinetic and thermodynamic studies of adsorption were also carried out, which depicted that the adsorption process of both dyes was exothermic in nature and followed pseudo-second-order kinetics. The results confirmed that NPs are easily fabricated through a green route and prove to be an excellent adsorbent for the removal of MO and MR dyes from their aqueous solutions. The maximum adsorption capacity of NPs synthesized was found to be 116.1 mg g⁻¹ and 74.02 mg g⁻¹ for MO and MR dyes, respectively.
Graphical abstract
... All adsorption experiments were conducted using triplicates, and the averages are reported. The removal efficiency and adsorption capacity of adsorbed fluoride were determined as following equations (Sohrabi et al. 2018a;Silva et al. 2017): ...
A novel adsorbent with excellent adsorptive properties for fluoride was prepared
through a green and cheap synthesis route. Populous caspica pruning wastes, a cheap
Agri waste material, reduced to multi-layer green graphene (MLG), and then postmodified to aluminum/iron modified multi-layer green graphene (AMLG and IMLG).
Batch experiments revealed the effect of pH (3-11), contact time (0.5-12 h), and initial
fluoride concentration (5-40 mg/L). The conversion of raw material to MLG increased
the specific surface area about 120 times (from 4 to 475 m 2 /g). Furthermore, a
significant improvement in zero points of charge (pHzpc) was attained for IMLG (7.1)
and AMLG (8) compared to pristine MLG (4.3). Fluoride showed superior affinity to
AMLG and IMLG compared to MLG. Fluoride removal increased gradually by pH from
3 to 8 and then decreased sharply up to pH 11. The study of process dynamics
demonstrated the monolayer fluoride adsorption onto AMLG and IMLG controlled by
the chemisorptions. The highest predicted adsorption capacities based on the
Langmuir model were 31.52, 47.01, and 53.76 mg/g for MLG, IMLG, and AMLG,
respectively. Considering economic and technical feasibility presents AMLG and IMLG
as a promising candidate against waters contamination by elevated fluoride.
... Different reports in the literature have reported on the utilization of the agro-residuals such as moong husk [5], raspberry biomass [6], wheat husk and rice husk [20], black bark waste [21], waste palm shells [22], Spirulina bio-blends [23] for producing bio-char, that can be utilized as adsorbents, soil conditioners and fertilizers. Not much work has been directed towards exploring RH derivatives as adsorbents for removing pollutants, in particular, pharmaceutical based products. ...
Employing sustainable techniques that utilize waste resources for the generation of valuable products are pivotal towards establishing economically-sound technologies. Moreover, directing these techniques towards creating entities that aid in alleviating environmental pollution concerns are highly desirable. Rice husks (RH) are abundantly available biomasses that are usually destroyed via inefficient means. Their utilization via thermochemical processes such as pyrolysis, yields fruitful, high-utility products like bio-char and bio-oil. Bio-char presents ideal platforms for developing highly-porous organic adsorbents. This work utilizes slow pyrolysis method for converting RH to bio-char under various temperatures in presence of a CO2 environment. Utilization of CO2 influences the textural and chemical nature of the developed bio-char and its deployment also lends an environmentally-conscious facet to this work, as it helps lower the overall carbon-footprint. As-prepared bio-char was activated in presence of an alkali that enhanced its overall surface area to 440 m2/g. Activated bio-char was utilized as an adsorbent for removal of commonly-found pharmaceutical pollutant, Ranitidine. Different parametric studies such as variation in pH, adsorbent dosage and pyrolysis temperature, were performed to understand their effect on adsorption capacity of prepared adsorbents. Adsorption of 50 ppm ranitidine on the activated bio-char at pH 9, resulted in the removal of 88.3% reactant, when 100 mg adsorbent dosage was provided. Activated bio-char displayed a maximum adsorption capacity of 65.8 mg/g under those conditions. Adsorption kinetics followed a pseudo-second order pathway while the adsorption isotherm could be described by the Langmuir model.
... Among adsorbents utilized for metal adsorption, chitosan is a biopolymer obtained from chitin deacetylation [26], which is regarded as a promising material due to its versatility, high efficiency, high selectivity, fast kinetic, availability, and cost-effectiveness [27]. It has metal chelating capacity since there exit a high content of amino and hydroxyl functional groups [28] in chitosan chain. ...
Textile with deodorizing properties not only keeps the clothing smell fresh, but also is beneficial toward improving the level of indoor air quality, especially when the fibrous materials are used for buildings and furniture. This review summarizes and discusses the recent progress in developing smart textile with deodorizing property. In particular, the key deodorizing methods including enhanced adsorption, catalytic decomposition, source control and masking are brought to light. The theoretical concepts, mechanisms and the latest fabrication methods along with the deodorizing efficiency are discussed. Moreover, the current limitations of these methods are underlined and some recommendations for future research strategies in terms of deodorizing performance, textile engineering, fiber types and treatment impact on fiber mechanical properties are proposed. This review provides the latest state-of-the-art achievements in the field of deodorizing methods of textile, which will be a valuable platform for researchers and decision makers to design and develop novel functional textile products.
... Linear regression has been one of the most viable tools defining the best-fitting relationship quantifying the distribution of adsorbates, mathematically analyzing the adsorption systems, and verifying the consistency and theoretical assumptions of a specific model (Foo and Hameed 2010). But, nonlinear optimization is a mathematically rigorous method to determine the parameters of the adsorption model using the original form of the equation (Lütke et al. 2019;Silva et al. 2017). Since in the nonlinear least square regression method, the selection of a ...
In the present paper, micro-mesoporous Fe-MIL-101/OAC composite using in situ incorporation of Fe-MIL-101 into oxidized activated carbon was synthesized and characterized by XRD, FT-IR, SEM, EDS, and BET techniques. The adsorption performances of toluene onto adsorbents in the gas phase were studied using a laboratory-scale dynamic adsorption system under moist ambience. The toluene adsorption capacity of Fe-MIL-101/OAC composite and Fe-MIL-101 were 127 and 97.6 mg g−1, severally. Results revealed that the larger pores in micro-mesoporous Fe-MIL-101/OAC enhanced the molecular diffusion rate. The findings indicated that micro-mesoporous structures played key roles in the capture of toluene molecules. The initial toluene concentration positively affected on toluene adsorption capacity while temperature and humidity negatively affected on toluene adsorption capacity. The Langmuir model and the pseudo-second-order kinetics model described better adsorption process of Fe-MIL-101/OAC composite. Thermodynamic findings determined that toluene adsorption over Fe-MIL-101/OAC was spontaneous, exothermic physisorption. The regeneration of the composite was still up to 72.6% after six cycles. The micro-mesoporous Fe-MIL-101/OAC composite proposes a promising support for the high toluene removal for future.
Graphical abstract
... The removal of dyes present in industrial effluents is a major environmental challenge, and because of this, there is a constant search for effective and economically viable processes (Kunz et al. 2002). There are several conventional methods of wastewater treatment employing chemical, Responsible editor: Tito Roberto Cadaval Jr physical, and biological processes, for example, coagulation techniques (Obiora-Okafo and Onukwuli 2018), filtration (Liu et al. 2017), adsorption (Silva et al. 2017;Carvalho et al. 2019), advanced oxidative processes (Doumic et al. 2019), exchange (Gomes et al. 2016;Hassan and Carr 2018), biological treatment (Hussein and Scholz 2018), and magnetic separation (Qiu et al. 2017). However, such routes generally have restrictions on their use due to various technical aspects, operating costs, and materials used (Souza et al. 2012). ...
Liquid effluents from various dyeing industries often have a high concentration of dyes that diffuse into river systems and can be toxic and non-degradable in the environment. In this study, the potential of the use of timbaúva seed husks in the preparation of four adsorbents tested in the removal of methylene blue was analyzed: in natura, chemically activated material (qmax = 1.24 ± 0.04 mg g−1), carbonized (qmax = 1.96 ± 0.03 mg g−1), and activated carbon (qmax = 1.983 ± 0.04 mg g−1). The adsorbents were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and CHN elemental analysis to assist in the proposed dye adsorption mechanism in the adsorbents tested. In the adjustment of the kinetic parameters, the pseudo-second order model was predominant by the statistical analysis of the ARE and R2. The carbonized samples were better adjusted to Langmuir isotherms. The removal efficiency of the methylene blue dye in aqueous solutions at the concentrations and conditions studied was 86.78%. The coal from the seed husks of timbaúva has shown excellent performance in adsorption of the methylene blue dye and, therefore, can have technological application.
... However, from pH 7, there is no significant variation on values of CV removal percentage. Under low pH values, there is a competition between the H + ions with the CV cationic dye (Brião et al. 2017;Silva et al. 2017), leading to lower adsorption values. When the pH is increased, this competition decreases and in parallel, the ChNW organic functional groups tend to be deprotonated. ...
Chitin (Ch) and chitin nanowhiskers (ChNW) were prepared, characterized, and applied as adsorbent to remove crystal violet (CV) dye from aqueous solutions. Ch was obtained from shrimp wastes and submitted to acid hydrolysis in order to find ChNW. The increase in average pore size and the rod-like shape of ChNW were probably the main characteristics which contributed to the increase in adsorption potential, when compared with raw Ch. The adsorbent dosage considered more adequate was 5 g L⁻¹, and the most suitable pH was 8.0. A pseudo-second-order model was adequate to represent the kinetic profile. Sips and Hill models were suitable to fit the equilibrium curves. The maximum adsorption capacity of CV on ChNW was 59.52 mg g⁻¹, and the process was endothermic, favorable, and spontaneous. These findings indicated that ChNW have potential to be used as adsorbent in the treatment of colored wastewaters.
... Fig. 2 show the DSC scans of the chitosan films before the adsorption (Fig. 3a), after the adsorptions using the binary system (Fig. 3b) and the effluent real (Fig. 3c). In all samples, endothermic bands centered around 63°C can be assigned to the evaporation of adsorbed water and residual solvent [40,41]. However, the thermal profiles performed after adsorption showed more extended bands. ...
Adsorption of Al (III) and Fe (III) onto chitosan films from individual and binary systems were investigated. The matrix effect was evaluated using an industrial effluent of the scrubber of gases from the production process of Al2(SO4)3. The adsorption study was carried out by response surface methodology to optimize the adsorption operation as a function of pH (3, 4.5 and 6) and film dosage (FD) (100, 200 and 300 mg L-1).The possible interactions film-ions were investigated by thermal analysis, X-ray diffraction, scanning electron microscopy and dispersive energy X-ray spectroscopy. The more suitable conditions for all experimental designs were the FD values in 100 mg L-1and pH 4.5.The adsorption capacity of Fe (III) in the individual and binary systems were 140.2 mg g-1 and 132.3 mg g-1 respectively; however, in the experiment conducted on the real effluent, the adsorption capacity was reduced to 66.30 mg g-1.Already to Al (III), the adsorption capacities in the individual and binary systems were 665.5 mg g-1 to 621.2 mg g-1 respectively, and when the operation was performed using real effluent the adsorption capacity was reduced to 275.7 mg g-1.
... In general, dyes represent a serious problem to human health and environmental safety; they can be toxic and carcinogenic and are recalcitrant molecules, making their removal difficult. Their presence in water, even at low concentrations, is toxic to living species and can cause inhibition of photosynthesis of aquatic species, reduction of dissolved oxygen and, therefore, poor overall oxygenation (Crini, 2006;Bello et al., 2011;Khan et al., 2011;Moussavi and Khosravi, 2011;Ali et al. 2012bAli et al. , 2014Ali et al. , 2016aAli et al. , 2017aAli et al. , 2017bSilva et al., 2017). ...
In this work, agro-wastes coming from soursop (peel, seeds and pulp fiber) and sugarcane (bagasse) are used as low-cost biosorbents to remove methylene blue (MB) from aqueous media. Batch experiments are performed under different experimental conditions investigating the effects of biosorbent amount, dye concentration and stirring rate. The best results were found using soursop wastes for a MB concentration of 100 mg L-1, using 0.75 g of residue and a stirring rate of 110 rpm, removing a percentage above 90%. Theoretically, adsorption kinetic can be successfully described by the pseudo-second order model. Redlich-Peterson and Sips models are adopted to interpret the equilibrium adsorption of MB on sugarcane bagasse and soursop residue, respectively. Interestingly, the monolayer model with single energy derived by statistical physics theory is also applied for a deeper explanation of the adsorption mechanism of MB on both the adsorbents. The application of this model allows defining the adsorption geometry of the investigated adsorbate and provides important information about the interactions between the adsorbate and sorbents. In particular, the modelling analysis by statistical physics allows defining that the dye molecules are adsorbed in vertical position and the adsorption process is multi-molecular (i.e. n>1). Finally, the estimation of adsorption energy suggested that MB adsorption on biosorbent is a physisorption process.
Bio-based materials are promising adsorbents due to their sustainability, environmentally friendly nature, low cost, and high removal efficiency. In this study, it was aimed to investigate the Capsella bursa-pastoris-filled chitosan biocomposite microbeads for the adsorptive removal of methylene blue dye from an aqueous solution. Firstly, the biocomposite beads were prepared by the addition of different weight ratios of Capsella bursa-pastoris in chitosan gel, followed by a cross-linking process. Then, optimum adsorption conditions were determined by performing studies under different conditions, namely, temperature (25–45 °C), pH (2–12), contact time (0–210 min.), adsorbent amount (0.010–0.300 g), and dye concentration (10–50 ppm). The experimental data were applied to non-linear and linear Langmuir and Freundlich isotherm models, and the most suitable isotherm model for the adsorption process was determined as well as to pseudo-first-order and pseudo-second-order kinetic models, and the mechanism of the adsorption process was determined. As a result of the studies, it was obtained that the adsorption capacity of the composites increased with the increasing amount of Capsella bursa-pastoris, and the maximum adsorption capacity was found as 222.22 mg/g at 25 °C. From the reusability studies, it was obtained that the composite beads remain efficient after the 5th cycle. This study suggests that Capsella bursa-pastoris-filled chitosan biocomposite microbeads are efficient and reusable adsorbents for the removal of methylene blue dye.
Graphical Abstract
Significant amounts of radioactive wastewater including uranium are discharged into the environment as a result of the expansion of large-scale nuclear power. Due to uranium's toxicity and bioaccumulation, it is crucial to develop efficient and long-lasting adsorbents with functional groups for improving the selective removal of U(VI). By successfully introducing amidoxime and phosphate groups into quaternary ammonium chitosan (QCS-AO/P, i.e., QAP), an antimicrobial composite nanofiber adsorbent (PQAP) composed of polyvinyl alcohol (PVA) and the as-prepared QAP was synthesized via the solution blow spinning technology (SBS) technique for the highly efficient recovery of uranium from wastewater. The influence of initial pH, contact time, and sorbent composition on the uranyl ion absorption and the antibacterial assay was studied. The PQAP composite fiber mat had the highest adsorption capacity of uranyl ions at pH 8 (559.26 mg/g), and showed excellent antibacterial activities. After six adsorption–desorption cycles, PQAP still retained a high uranium adsorption capacity of 420 mg/g and elimination efficiency (84%). The novel integrated sorption and antibacterial strategy provides new insights for highly efficient treatment of radioactive wastewater.
A novel modified chitosan (CS) material, CS-g-AOPAM, was prepared by the amidoximation of the crosslinking compound of CS and a terpolymer of acrylamide, acrylonitrile and 3-dimethylaminoallyl phosphonic acid, which was applied to adsorb Cu(II) and Ni(II). The material CS-g-AOPAM was characterized by SEM, FTIR, XPS and TG, indicating porous structure and excellent thermal stability. In order to investigate the effects of coexisting ions, pH, initial concentration, adsorption time, and temperature on adsorption capacity of CS-g-AOPAM, batch adsorption experiments were carried out to obtain the corresponding adsorption behavior. According to the linear fitting of Langmuir model, the results proved that CS-g-AOPAM had excellent adsorption performance, exhibiting the maximum adsorption capacities of 215.5 mg·g⁻¹ and 213.4 mg·g⁻¹ for Cu(II) and Ni(II), respectively, which was higher than that of most similar CS adsorbents. The adsorption isotherms were in good agreement with Langmuir model, indicating a monolayer adsorption. Moreover, various adsorption kinetic and thermodynamic models were employed for analyzing adsorption behavior of CS-g-AOPAM, suggesting that the adsorption was a chemisorption as well as spontaneous endothermic process. Further, based on the analysis of FTIR and XPS, the adsorption sites and potential bonding modes of Cu(II) and Ni(II) were proposed. Overall, CS-g-AOPAM is a pretty promising novel adsorption material for the removal of heavy metal ions from wastewater.
The pollution of wastewater by heavy metal ions is hazardous to the environment and human health. Cd(II) has been recognized as one of the heavy metals that causes severe toxic effects. The present study is aimed at removing Cd(II) from wastewater using fungal biomass either immobilized on loofa sponges or in Ca-alginate beads. Two fungal species were isolated from pools of Cd(II)-polluted wastewater obtained from some Egyptian industrial plants, and using internal transcribed spacer (ITS) primers, they were molecularly identified as Penicillium chrysogenum and Cephalotheca foveolata with accession numbers MT664773 and MT664745, respectively. The sorbents used in this study were heat-inactivated mycelia of P. chrysogenum (PEN), heat-inactivated mycelia of C. foveolata (CEP), P. chrysogenum immobilized on loofa sponge (PEN-ILS), C. foveolata immobilized on loofa sponge (CEP-ILS), P. chrysogenum immobilized in Ca-alginate beads (PEN-IA), and C. foveolata immobilized in Ca-alginate beads (CEP-IA). The effects of pH, contact time, initial Cd(II) concentration, and interfering ions on Cd(II) removal from aqueous solution were tested. Maximum Cd(II) sorption capacity was obtained at pH 7.0, with thirty minutes contact time and 0.5 mol l⁻¹ initial Cd(II) concentration for all sorbents used. However, Ca²⁺ displayed synergistic interference with Cd(II) that was greater than that from Na⁺ and K⁺, with decreasing sorption capacity for all sorbents. Optimum conditions were applied to real wastewater samples collected from two Egyptian industrial plants. All sorbents had the ability to remove Cd(II) from wastewater samples, and enhanced removal occurred when fungal cells were immobilized as compared to free cells.
Xanthate-modified cross-linked chitosan（chitosan-SH）was synthesized by hydrothermal method. The adsorption mechanism and capacity of removing ruthenium [Ru(Ⅲ)] from aqueous solutions with chitosan-SH as an adsorbent was investigated. The characterization results indicated that carbon disulfide (CS2) was successfully loaded into cross-linked chitosan. Structural characterization of the samples was performed by Fourier transform infrared (FTIR), X-ray photoelectron spectrometer (XPS), scanning electron microscope (SEM), specific surface area and porosity analysis (BET) analysis methods. The results of kinetics data suggested that the ruthenium ion adsorption process by chitosan-SH could be fast to reach equilibrium within 30 min. Additionally, the removal percentage of uranium was obtained 94.7% at pH 7.0. Several parameters affecting adsorption capacity, including pH, contact time, initial Ru(Ⅲ) concentration and solution volume, and adsorbent concentration, were also investigated. Overall, chitosan-SH could be applied as a superior adsorbent for Ru(Ⅲ) in wastewater.
In this study, ternary phase Fe2O3-Mn2O3-Mn3O4 (FMM) nanocomposites (NCs) were synthesized via a facile co-precipitation method. The surface of synthesized NCs was modified by cationic CTAB surfactant to increase surface functionality and surface area without any phase change. The existence of the ternary phase in NCs was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. Additionally, characterization techniques such as Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET) surface area analysis, point of zero charge, Field Emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) were examined for FMM NCs and CTAB modified FMM NCs. The FT-IR and BET surface area analysis confirmed that CTAB modified FMM NCs showed excellent functionality and 19.11% higher surface area than unmodified FMM NCs. Thus, the prepared both NCs were used for congo red (CR) dye adsorption from aqueous solution by varying batch experimental parameters, such as initial pH, contact time and temperature with varying the initial concentration of dye. For kinetic rate analysis, the equilibrium time data were fitted with non-linear form of kinetic models such as pseudo-first-order, second-order, and Elovich model. The equilibrium concentration data were fitted with non-linear equation of Langmuir, Freundlich, and Temkin isotherm models. The maximum adsorption capacity of both NCs increased with increasing temperature; increased from 465.39 to 544.5 mg/g and 627.36–705.84 mg/g for FMM NCs and CTAB modified FMM NCs, respectively, with increasing temperatures from 20 to 40 °C. The thermodynamic parameter studies confirmed that spontaneous adsorption of CR onto both NCs. The adsorption capacity of both NCs was also checked by other anionic and cationic dyes. The effect of co-existing anions on the adsorption capacity of both NCs for CR dye adsorption was also investigated in the present work. The regeneration study of both FMM and CTAB modified FMM NCs were accomplished by NaOH, KOH, ethanol, and double-distilled water; reusability experiments of regenerated NCs were also performed.
Chitosan and montmorillonite nanoparticles (MMT NPs) films are prepared using casting method with various weight percentage (10, 20, 30, 40, 50, 60, 70 wt%) of MMT NPs. XRD and FTIR-ATR studies have been conducted to investigate the structural changes for the prepared films. XRD and FTIR-ATR confirmed the existence of interaction between Chitosan and MMTNPs and changing in structure of prepared composite depending upon the percentage of the load MMTNPs in Chitosan. Moreover, the films of high MMT NPs doping are used for the iron adsorption process from ground water. The effect of PH, temperature, adsorbent dose and the initial concentration of adsorbant have been studied. Langumiur and Frendulich are applied to investigate the adsorption process. The adsorption process is aligned with Langumiur isotherm. Fe adsorption process matched with the pseudo first order kinetic Thermodynamics parameters of the adsorption process are calculated indicating that the adsorption process is spontaneous and endothermic. The percent weight ratio (40/60 wt%) chitosan/MMT NPs is found to be the best proper ratio for adsorption of iron which attained 89.2 % at the optimum conditions (1.5 g/L dose, pH 5.5 and 10 mg/L Fe after 210 min). HRSEM, EDX and FTIR-ATR before and after adsorption process was high evidence tools for confirming the adsorption.
There are large amounts of waste shrimp shells in the coastal cities or countries. In this study, the waste shrimp shells were used to produce the chitosan (CS), on which MnFe2O4 was coated, forming novel adsorbents - MnFe2O4/CS microspheres (MCMS). The adsorption performance of Cu(II) and Cd(II) onto MCMS was investigated by batch experiments, which focused on the adsorption influence parameters, adsorption isotherm, thermodynamic parameters, adsorption kinetics and adsorption regeneration. The characterization of CS and MCMS was determined by XRD, FTIR, SEM/EDS, XPS, and BET, and determined deacetylation degree and molecular weight of CS. The results showed that the adsorption is a spontaneous exothermic process, which could be described well by pseudo-first-order model and Langmuir model. The maximum adsorption capacities of Cu(II) and Cd(II) were 62.3 and 60.6 mg g⁻¹, respectively. The regeneration experiments indicated that MCMS could maintain adsorption capacities after 3 cycles of adsorption - regeneration. BCR sequential extraction procedure for MCMS adsorbing heavy metals from sediments showed that the MCMS could absorb the Cu and Cd metals selectively in the following fractions: weak acid extracted, reducible and oxidizable.
Adsorption of fluoride from fertilizer industry effluent using carbon nanotubes stabilized in chitosan sponge as adsorbent was evaluated. The effluent was produced in the washing of acid gases during the reaction in fertilizer production and all assays were performed using this hazardous material. Adsorbent characterization and ions interactions were elucidated from differential scanning calorimetry, thermal gravimetric analyses, X–ray diffraction, scanning electron microscopy dispersive energy X–ray spectroscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The effluent presented pH 3 and its value not changed in the adsorption assays, maintaining the conditions of the process. The kinetics assays of fluoride from industry effluent were performed in different stirring rates from 100 to 300 rpm. It was observed that adsorption was initially fast reaching the equilibrium at 300 rpm in 20 min. The adsorption capacity was around 975.4 mg g-1, showing the potential of the hybrid material to remove fluoride from a real matrix. The high adsorption capacity was attributed to the chitosan functional groups and the high interaction area promoted by sponge form and the carbon nanotube. Reuse and regeneration of the CNT-CS were investigated and 5 cycles were obtained. The adsorption capacity kept similar values in all cycles.
Introduction of functional moiety to covalent organic framework (COFs) is of great significance for promoting their wide applications. Here we show one-pot synthesis of carboxyl-functionalized COF-TzDBd via direct condensation of 1,3,5-tris(4-formyl-phenyl) triazine (Tz) and 4,4'-diamino-[1,1'-biphenyl]-2,2'-dicarboxylic acid (DBd). The prepared TzDBd showed good crystallinity, mesoporous pores and high chemical stability. It was applied for ultrafast adsorption and efficient elimination of triphenylmethane dyes. The adsorption isotherms, adsorption thermodynamics, kinetics, and reusability of the prepared carboxyl-COF were investigated in detail. The adsorption of crystal violet (CV) and brilliant green (BG) on TzDBd followed the pseudo-second-order adsorption kinetic model and reached equilibrium within 2 min at the initial concentration of 100 mg L-1. The adsorption of triphenylmethane dyes on TzDBd fitted well with Langmuir adsorption model and gave the maximum adsorption capacities of 307 and 276 mg g-1 for CV and BG, respectively. The predesigned mesoporous pores, conjugated phenyl structure and the negatively charged carboxyl groups on TzDBd significantly facilitate the adsorption kinetics for large cationic triphenylmethane dyes. The ultrafast kinetics, high adsorption capacity and good reusability endow the carboxyl-functionalized COF with great potential for removing triphenylmethane dyes from aqueous environment.
Electrospun chitosan/poly(ethylene oxide) nanofibers were synthetized, characterized and applied as alternative biosorbents to remove pigments from pretreated crude glycerol. The pigments removal efficiency of electrospun nanofibers was examined by comparing the adsorption capacity of nanofibers with other chitosan–based biosorbents. Pseudo–first order, pseudo–second order and Elovich models were used to estimate kinetic parameters. The nanofibers exhibited continuous fibers, with the average fibers diameter of 526 ± 101 nm. The results also indicated interactions between chitosan and poly(ethylene oxide) molecules, without changing the main adsorptive sites of chitosan. Furthermore, chitosan/poly(ethylene oxide) nanofibers exhibited higher relative adsorption capacity (120 g⁻¹) than chitosan powder (35 g⁻¹) and chitosan biopolymeric film (58 g⁻¹). The pseudo–first order and Elovich models were the most suitable models to represent the kinetic behavior of the composite nanofiber.
In this research, different chitosan samples were obtained and were applied to produce biopolymeric films, aiming to obtain environmentally friendly materials for packaging applications. Chitosans were obtained by different conditions from the alkaline deacetylation of chitin. The chitosan films were prepared from all chitosan samples by casting technique. The results showed that the molecular weight of chitosan samples increased as a function of the increase in the chitin diameter and of the decreases in the NaOH:chitin ratio, NaOH concentration and reaction time, and its values were in the range from 101 to 201 kDa. For the deacetylation degree of chitosan an inverse behavior was observed, and its values ranged from 64.0 to 95.9 %. The best values were obtained for the films when chitosan with highest molecular weights and lowest deacetylation degrees were used. In this condition, the film was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and thermal analysis (TGA and DSC). The films produced had physical–mechanical properties acceptable for use in active food packaging.
In this work, spouted bed and tray-drying techniques were employed at different drying air temperatures to produce dried chitosan, and the chitosan powder was used to produce biofilms. The products obtained from each drying technique were compared in relation to quality aspects (molecular weight, lightness, and hue angle). The results found for chitosan in spouted bed drying (90°C) showed lower alteration and best quality aspects in relation to the chitosan powder. However, in tray drying under the best condition (60°C) the chitosan molecular weight increased about 50% in relation to the initial value and browning was observed. The biofilms produced from chitosan dried in the spouted bed showed the best mechanical properties (tensile strength of 42 MPa and elongation of 29%) and lower water vapor permeability (3.95 g mm m kPa day).
The adsorption of copper ions on Spirulina platensis was studied as a function of contact time, initial metal ion concentration, and initial pH regimes. Characterization of this adsorbent was confirmed by FTIR spectrum. Modified Gompertz and Logistic models have not been previously applied for the adsorption of copper. Logistic was the best model to describe experimental kinetic data. This adsorption could be explained by the intra-particle diffusion, which was composed of more than one sorption processes. Langmuir, Freundlich, and Redlich–Peterson were fitted to equilibrium data models. According to values of error functions and correlation coefficient, the Langmuir and Redlich–Peterson models were more appropriate to describe the adsorption of copper ions on S. platensis. The monolayer maximum adsorption capacity of copper ions was determined as 67.93 mg g−1. Results indicated that this adsorbent had a great potential for removing of copper as an eco-friendly process.
A filamentous microorganism, morphologically similar to the cyanobacterium Arthrospira, was isolated from Mangueira Lagoon in Brazil, from which Arthrospira has not previously been isolated. Random amplified polymorphic DNA (RAPD) comparison with the standard Arthrospira platensis strains LEB 52 and Paracas indicated that the organism isolated was an Arthrospira isolate, which we denominated strain LEB 18. The RAPD analysis showed conserved sequences which indicated that the three strains belonged to the same genus, and were all Arthrospira species, but there were sufficient differences between them suggesting that they were separate strains. The strain LEB 18 was cultivated in undiluted Zarrouk medium and in 60% and 20% (v/v) Zarrouk medium diluted with sterilized Mangueira Lagoon water (MLW) using illuminance rates of 32.5, 45.5 and 58.5 micromol m(-2) s(-1) according to a complete 32 factorial design with a triplicate central point. The strains LEB 52 and Paracas were cultived in the conditions central point. Our new isolate produced the highest specific growth rate (Umax = 0.22 d(-1)) in 60% Zarrouk medium diluted with MLW and illuminated with 58.5 micromol m(-2) s(-1) and the highest protein content (86.0% w/w).
In this work, the kinetics of thermal degradation of chitin and chitosan polymers were investigated by means of Fourier Transform Infrared Spectroscopy and thermogravimetric analyses in air atmosphere, under dynamic conditions in the range of 298–873 K. The kinetic parameters, such as the apparent activation energy (Ea) and pre-exponential factor (A) were determined using Ozawa–Flynn–Wall (OFW) and Kissinger–Akahira–Sunose (KAS) isoconversional methods. The experimental data were found, in the range of conversion fraction 0.1 < (<0.8, to be well described by the modified catalytic Sestak–Berggren (SB) model adapting the conversion function, f(α) = cαm(1−α)n with the adjusted values of m, n and c. It was found that the simulated curves issued from the model best fit those issued from the experimental data, indicating the same scission mechanism for the degradation of chitin and chitosan. It was found that the average value of Ea = 125 kJ/mol used in the simulated curves of chitin, Y (α) and Z (α), is comparable to those calculated by KAS and OFW, while for chitosan, it represents the mean value (Ea = 169 kJ/mol) between the values of Ea calculated by KAS (Ea = 191.61 kJ/mol) and OFW (Ea = 146.50 kJ/mol) methods.
In this work, a new kind of magnetic amine/Fe3O4 functionalized biopolymer resin (amine/Fe3O4-resin) was prepared and applied to remove various anionic dyes from water. Methyl Orange (MO), Reactive Brilliant Red K-2BP (RBR) and Acid Red 18 (AR) were selected as the typical anionic dye for this research. Meanwhile, amine/Fe3O4-resin was characterized by VSM, XRD, FT-IR, SEM, TEM and XPS. Three anionic dyes removed by amine/Fe3O4-resin were investigated using batch adsorption technique, and the parameters including adsorbent dosage, pH, contact time and temperature were considered. Due to a large number of amine groups and high surface areas, amine/Fe3O4-resin exhibited a remarkably high adsorption capacity for all three dyes, reaching 101.0 mg/g, 222.2 mg/g and 99.4 mg/g for RBR, MO and AR at 25°C, respectively. The pseudo-second order model and Langmuir model agreed well with the experimental data, and regeneration experiments indicated its merit of separability and reusability.
This volume is designed to serve as an introductory text in the field of SEM and X-ray microanalysis. It deals with the user-controlled functions of the electron optics, the characteristics of electron-beam-sample interactions, image formation and interpretation, X-ray spectrometry, and quantitative X-ray microanalysis. Specimen preparation and coating techniques for SEM and microanalysis are also described together with procedures for both energy-dispersive and wavelength-dispersive X-ray spectrometry. Appendices give X-ray energies of principal lines, mass absorption coefficients, backscattering factors, etc.R.A.H.
Basic dye, methylene blue (MB), has been known as the most common parameter used to measure the extent of mesoporosity (20-500 Å) of activated carbon (AC). The adsorption performance in terms of uptake along with its dependence on heating techniques has been reviewed for MB on activated carbons prepared by chemical activation of agricultural wastes. Recently, microwave heating has been adopted as an alternative technique for conventional heating, where the latter suffered from thermal gradient, long activation time, high cost, and fast firing. Equilibrium, kinetic, and thermodynamic of adsorption process for MB-AC system were analyzed. The effects of most significant preparation variables on pore structure of AC and adsorption performance were also presented. Conclusively, important observations have been reported for dependence of adsorption performance and mechanism on preparation and adsorption variables for studied system.
Azo dyes are aromatic compounds with one or more –NN– groups. These dyes are the most important and largest class of synthetic dyes used in commercial applications. Several methods have already been used to treat textile effluents including physico-chemical methods such as filtration, carbon activated, coagulation and chemical flocculation. Although these methods are effective, but they are expensive and involve formation of concentrated sludge that creates a secondary disposal problem. In recent years, use of bioremediation based technologies for treating textile wastewater containing dyes has attracted much interest. The ability of microorganisms and their dye degrading enzymes to decolorize and metabolize the dyes has long been known and has proved to be the best option for bioremediation. As far as decolorization and degradation of textile dyes are concerned, azoreductases, laccases, peroxidases and many other important enzymes seem to have shown great potential to decolorize the textile dyes and these enzymes are considered as effective molecular weapon for bioremediation of azo dyes.
The interaction between cells and biomaterials plays a key role in cell proliferation and differentiation in tissue engineering. However, a quantitative analysis of those interactions has been less well studied. The objective of this study was to quantitative recapitulate the difference of MC3T3-E1 cell adhesion, morphological and biomechanical properties on chitosan-collagen films in terms of chemical composition. Here, the unbinding force between MC3T3-E1 cell and a series of chitosan-collagen films was probed by a real-time and in situ atomic force microscopy-single cell force spectroscopy (AFM-SCFS). Meanwhile, changes in cell morphology and Young's modulus on different chitosan-collagen films were detected by AFM. The cell area and CCK-8 results showed that cell spreading and proliferation increased with increasing collagen content. AFM observations clearly showed cell height decreased and pseudopod fusion with the collagen content increased. Cell adhesive force increased from 0.76±0.17nN to 1.70±0.19nN. On the contrary, cells Young's modulus, which reflected biophysical changes of cells decreased from 11.94±3.19kPa to 1.81±0.52kPa, respectively. It suggested that stronger cell-substrate interactions benefit cell adhesion, and better cell flexibility improve cell spreading. The findings indicate that cell morphology, adhesive force and Young's modulus are significant affected by various chitosan-collagen substrates. Those methods and quantitative results have guiding significance for investigating the mechanism of chitosan and/or collagen based cell-targeting drug carrier and the preparation of chitosan-collagen composite biomaterials.
Copyright © 2015 Elsevier B.V. All rights reserved.
Biosorption is an emerging green technology to remove organic dyes from effluents. However, many efforts are still necessary to make biosorption an attractive option in relation to the conventional treatment processes. This chapter presents some important aspects regarding biosorption technology. Firstly, the general aspects of biosorption are presented. Secondly, the classification, advantages and properties of the biosorbents are discussed. Factors affecting biosorption are explained, after which studies on equilibrium, thermodynamics, kinetics and mechanisms are addressed. Finally, future perspectives and challenges are presented. It is expected that this information will assist future research in the biosorption field.
In our era of rapidly expanding technology, the scientist must observe, analyze, and correctly explain phenomena occurring on a micrometer (µm) or submicrometer scale. The scanning electron microscope and electron microprobe are powerful instruments which permit the observation and characterization of heterogeneous organic and inorganic materials and surfaces on such a local scale. In both instruments, the area to be examined or the microvolume to be analyzed is irradiated with a finely focused electron beam, which may be static or swept in a raster across the surface of the specimen. The types of signals produced when the electron beam impinges on a specimen surface include secondary electrons, backscattered electrons, Auger electrons, characteristic x rays, and photons of various energies. These signals are obtained from specific emission volumes within the sample and can be used to examine many characteristics of the sample (composition, surface topography, crystallography, etc.).
Sulfur dyes are inexpensive and are used mainly for dyeing textile cellulosic materials or blends of cellulosic fibers. Sodium sulfide is fairly cheap and a traditional reducing agent used for sulfur dyeing, but it is toxic and hazardous to handle. Its use may leave harmful residues in finished fabrics and generate effluents that are difficult to treat and damaging to the environment. Textile companies face the high costs of water and wastewater, as well as strict environmental legislation. In this review, a variety of methods, including physicochemical and biological methods, are surveyed for their application to the treatment of water and wastewater containing sulfur dyes. This survey is followed by suggestions for further actions that can be taken for the improvement of the treatment processes from both economic and technical viewpoints.
Chitosan films were applied to remove acid red 18 and FD&C blue no. 2 dyes from aqueous solutions. The films were prepared by casting technique and characterized. Batch adsorption equilibrium experiments were carried out at different temperatures (298–328 K). Freundlich, Langmuir and Redlich–Peterson models were fitted to the experimental data. The thermodynamic parameters (ΔG0, ΔH0 and ΔS0) were also estimated. Kinetic study was realized using pseudo-first order, pseudo-second order and Elovich models. The possible films–dyes interactions were investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry and color parameters. The maximum experimental adsorption capacities were 194.6 mg g−1 and 154.8 mg g−1 for the acid red 18 and FD&C blue no. 2, respectively, obtained at 298 K. It was found that the Redlich–Peterson isotherm model presented satisfactory fit with the experimental data (R2 > 0.98 and ARE < 9.00%). The adsorption process was spontaneous, favorable, exothermic, and occurred by electrostatic interactions. The Elovich model was the more appropriate to represent the adsorption kinetic data (R2 > 0.95 and ARE < 5.00%). The chitosan films maintained its structure and were easily separated from the liquid phase after the adsorption process.
The thermal degradation of chitosan, degree of acetylation 12%, was studied by using TG in nitrogen atmosphere in isothermal and dynamic conditions. Temperatures ranging from 240 °C to 280 °C were studied in isothermal conditions while heating rates in the interval 2.5–15.0 °C/min were employed when using dynamic conditions. The data issued from the dynamic experiments were treated by the methods proposed by Ozawa–Flynn–Wall and Kissinger, resulting in apparent activation energy of 149.6 kJ/mol and 138.5 kJ/mol, respectively. The approach proposed by MacCallum was used to treat the data issued from the isothermal experiments, resulting in Ea = 153 kJ/mol in good agreement with the results issued from the dynamic experiments. The use of the isoconvertional method due to Vyazovkin also showed a good agreement with the value of the activation energy issued by applying the method of Ozawa–Flynn–Wall. It was also observed that regardless of using isothermal or dynamic experimental conditions, the kinetic model best suited to describe the thermal degradation of chitosan is the catalytic Šesták–Berggren model.
Crystallized silver nanoparticles (SNPs) have been biosynthesized by Spirulina platensis in an
aqueous system. An aqueous solution of silver ions was treated with a live biomass of Spirulina platensis
for the formation of SNPs. These nanoparticles showed an absorption peak at 430 nm in the UV-visible
spectrum, corresponding to the plasmon resonance of SNPs. The transmission electron micrographs of
nanoparticles in an aqueous solution showed the production of SNPs (average size of most particles:
∼12 nm) by Spirulina platensis. The X-Ray Diffraction (XRD) spectrum of the nanoparticles confirmed the
formation of metallic silver, and the average size of the crystallite was estimated from the peak profile by
the Scherrer method. The synthesized SNPs had an average size of 11.6 nm.
The aims of this work were to develop gelatin films using glycerol as plasticizer (0–100% based on protein mass) and to establish relationships between glycerol content and structural, barrier, thermal and mechanical film properties. These correlations were established since WVP exhibited a minimum for films containing 20 g glycerol/100 g gelatin, while flexibility increased from 2.2% to 180.9% and Tg shifted from 137.5 to 21.3 °C, for films without glycerol and plasticized films with 80 g glycerol/100 g gelatin, respectively. Furthermore, a satisfactory fit between Tg experimental data and predicted values by Couchman and Karasz's equation was found, with glycerol ranging from 0 to 60 g/100 g gelatin. Tg values correlated inversely with film moisture content, and both mechanical and thermal properties showed a strong dependence since elastic modulus and Tg followed a similar trend. Films exhibited similar X-ray patterns regardless of the glycerol concentration, showing a displacement in the position of the peak located at around 2θ=8°, which shifted towards lower 2θ values with glycerol content.The abovementioned correlations between film physical properties and glycerol content, would allow to select the optimum conditions to develop, process and manage gelatin films according to specific requirements.
The capability to produce blend chitosan–whey protein films at acidic pH, carrying a high amount of protein, is demonstrated, even though under these conditions a pure whey protein film could not be obtained. The films are biphasic and characterized by a compositional gradient, with the downward film surface containing a lower amount of protein than the upward surface. The surface richer in protein was more hydrophobic than that richer in chitosan. The difference in composition and hydrophilicity between both surfaces increases with the amount of protein incorporated in the film. Increasing the protein amount decreased elongation at break and tensile strength but, in general, had little effect on water vapor permeability. Although some of the film functionality might be compromised due to the incompatibility between the polysaccharide and protein components within the film matrix, the blended films, especially those with intermediated protein amount, may have useful applications on those food systems where the edible films should break up during the cooking or mastication process.
Various infrared spectroscopic techniques for the analysis of degree of N-deacetylation of chitosan were evaluated for accuracy.
A new method was proposed which involved development of a calibration curve using the absorbance intensities of the chitosan
infrared spectrum at 1655 and 3450 cm−1. The degree of N-deacetylation of various chitosan samples was then determined by using the absorption ratios [A1655/A3450] in the equation of the calibration curve. This method yielded results which were superior to those of any of the previously
reported infrared spectroscopic methods tested herein.
The adsorption of azobenzene FD&C Red No. 40 (C.I. 16035) from aqueous solutions by chitosan was studied through adsorption isotherms. The effects of pH (5.7, 6.6 and 7.5), particle size ranges (0.10 ± 0.02, 0.18 ± 0.02 and 0.26 ± 0.02 mm), deacetylation degree (42 ± 5%, 64 ± 3% and 84 ± 3%) and temperature (25, 35 and 45 °C) were investigated. Langmuir, Freundlich and Redlich–Peterson (R–P) adsorption models were applied in order to describe the experimental isotherms and isotherm constants. Coefficients of determination (R2 > 0.95) and mean relative error (MRE < 0.10) values showed that Langmuir and R–P models presented better fit with the experimental data. The maximum monolayer adsorption value has been found to be 529 mg g−1, at pH 6.6, temperature 35 °C, particle size range 0.10 ± 0.02 mm, and deacetylation degree 84 ± 3%.
Chitosan was cross-linked using glutaraldehyde in the presence of magnetite. The resin obtained was chemically modified through the reaction with tetraethylenepentamine followed by glycidyl trimethylammonium chloride, to produce chitosan/amino resin (R1) and chitosan bearing both amine and quaternary ammonium chloride moieties (R2), respectively. The uptake of Reactive Black 5 (RB5) from aqueous solutions using R1 and R2 resins was studied using batch and column methods. The resins showed high affinity for the adsorption of RB5 where an uptake value of 0.63 and 0.78 mmol/g was reported for resins R1 and R2, respectively at 25 °C. Both kinetics and thermodynamic parameters of the process were estimated. These data indicated an endothermic spontaneous adsorption process and kinetically followed the pseudo-second order model. Breakthrough and regeneration curves for the removal of RB5 were studied. The adsorbed dye was eluted from the investigated resins effectively.
The biosorption of food dyes FD&C red no. 40 and acid blue 9 onto Spirulina platensis nanoparticles was studied at different conditions of pH and temperature. Four isotherm models were used to evaluate the biosorption equilibrium and the thermodynamic parameters were estimated. Infra red analysis (FT-IR) and energy dispersive X-ray spectroscopy (EDS) were used to verify the biosorption behavior. The maximum biosorption capacities of FD&C red no. 40 and acid blue 9 were found at pH 4 and 298 K, and the values were 468.7 mg g(-1) and 1619.4 mg g(-1), respectively. The Sips model was more adequate to fit the equilibrium experimental data (R2>0.99 and ARE<5%). Thermodynamic study showed that the biosorption was exothermic, spontaneous and favorable. FT-IR and EDS analysis suggested that at pH 4 and 298 K, the biosorption of both dyes onto nanoparticles occurred by chemisorption.
Spirulina is the most extensively used microalgae for animal and human nutrition mostly because of its high protein content, 60-65% on a dry weight basis. The drying is the most expensive operation. The aim of the study was to characterize drying of Spirulina platensis in thin layer. A Statistical model was applied to analyze the effects of independent variables (air temperature and loads of solids in the tray) on the response of solubility in acid medium. The analysis of phycocyanin content was determined at the best drying condition. The Spirulina isotherm data were adjusted through Guggenheim, Anderson and de Boer (GAB) and Brunauer, Emmett and Teller (BET) correlations. The nonlinear regression analysis of isotherms data showed that the GAB equation more effective adjusted the experimental data (R(2)>99% and E%<10%). Drying curves of Spirulina showed only a decreasing rate-drying period. The material load and the interaction between the air temperature and material load were significant effects (P0.05), and the best results of solubility in acid medium ( approximately 79%) occurred at 60 degrees C and 4 kg/m(2). In under these conditions the phycocyanin content was determined to be 12.6% of dried Spirulina.
A commercially available almond emulsin beta-glucosidase preparation has been reported to have chitobiose activity, and can hydrolyze chitin substrates due to a chitinase present in the enzyme preparation. This beta-glucosidase preparation was used to investigate hydrolytic activity on five chitosan samples with different molecular weight and degree of deacetylation. The degree of deacetylation and molecular weight of the chitosan samples were determined using a circular dichroism and a viscometric method, respectively. The hydrolytic activity of this beta-glucosidase preparation on chitosan was monitored viscometrically as the most convenient means of screening. Solutions of chitosan in pH 5.0 acetate buffer were prepared using the different viscosity grades of chitosan. The specific viscosity, measured after addition of beta-glucosidase to the above solutions, decreased dramatically over time in comparison to that of the respective control mixture without enzyme. Eadie-Hofstee plots established that hydrolysis of chitosan by this enzyme preparation obeyed Michaelis-Menten kinetics. Apparent Michaelis-Menten parameters and initial degradation rates were calculated and compared to determine the influences of the degree of deacetylation and molecular weight on the hydrolysis. The results show that higher molecular weight and higher degree of deacetylation chitosans possessed a lower affinity for the enzyme and a slower degradation rate. Faster degradation rates, then, are expected with lower molecular weight and low degree of deacetylation chitosans. Hydrolysis of these chitosan samples confirms the existence of a chitinase in the almond emulsin beta-glucosidase preparation, and further studies are warranted.
A series of chitosan-gelatin composite films was prepared by varying the ratio of constituents. FT-IR and X-ray analysis showed good compatibility between these two biopolymers. Differential scanning calorimetry (DSC) analysis indicated that the water take-up of chitosan film increased when blended with gelatin. Composite film exhibited a lower Young's modulus and a higher percentage of elongation-at-break compared with chitosan film, especially in wet state. All composite films were hydrophilic materials with water contact angles ranging from 55 degrees to 65 degrees. The results obtained from ELISA indicated the adsorption amount of fibronectin on composite films was much higher than on chitosan film. PC12 cells culture was used to evaluate the nerve cell affinity of materials. The cells cultured on the composite film with 60wt% gelatin differentiated more rapidly and extended longer neurites than on chitosan film. The results suggest that the soft and elastic complex of chitosan and gelatin, which has better nerve cell affinity compared to chitosan, is a promising candidate biomaterial for nerve regeneration.
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