Juan A. Melero

King Juan Carlos University | URJC

Bioplastics are a promising and sustainable alternative to traditional plastics derived from petroleum. Particularly, polyhydroxyalkanoates (PHA) produced from purple phototrophic bacteria (PPB) and low-value substrates have gained attention as a viable option. However, concerns remain about the scalability and environmental feasibility of this pro...

Mesoporous silica-supported Zr-MOF-808 catalysts have been synthesised and tested in the aldol condensation of (biomass-derived) furfural and methyl isobutyl ketone to bio-jet fuel precursors. Growth of Zr-MOF-808 nanocrystals over silica scaffolds results in well-dispersed Zr species which confer strong Lewis acidity as determined by FTIR of chemi...

Refinery wastewater (RWW) treatment is outdated since new wastewater management and reuse challenges require more environmental-friendly and cheap alternatives. Conventional biological treatments focused on activated sludge are highly energy-intensive and resource-dissipating processes. However, anaerobic treatments are an excellent alternative to...

Polyhydroxyalkanoate (PHA) production at a large scale by purple phototrophic bacteria (PPB) is hindered due to high production costs and limited recovery due to its consumption during starvation periods. The present study identified cost-effective inorganic acids as inactivation methods for PPB to obtain higher PHA recovery. The study was performe...

In this study, a photoanaerobic PPB-based biological system for the treatment of refinery wastewater and oily sludge pretreated by thermal hydrolysis has been studied within the framework of sustainability.

g‐Valerolactone (GVL) is a renewable and versatile platform chemical derived from sustainable carbon feedstocks. The cascade conversion of levulinic acid into GVL requires Brønsted and Lewis acid catalysed reactions. Here, we demonstrate a dual‐catalyst bed configuration that promotes synergy between Brønsted acid sites in sulfated zirconia (SZ) an...

Purple phototrophic bacteria (PPB) are a novel driver to recover organics and nutrients from wastewater by assimilative growth. Depending on the source, assimilated resources from the PPB biomass can still be recovered after a releasing step. Anaerobic digestion (AD) releases carbon and nutrients, but the release is incomplete. Thermal hydrolysis (...

The production of polyhydroxyalkanoates (PHA) with purple phototrophic bacteria (PPB) has been limited due to low yields and limited knowledge regarding the diverse routes used for carbon biosynthesis. The present study increases PHA accumulation yields using urban organic waste pretreated by steam explosion and acidogenic fermentation as substrate...

The solvent-free production of diphenolic acid (DPA) from levulinic acid (LA) and phenol is studied using readily accessible commercial acid zeolites like Beta, ZSM-5 and USY. Acid zeolites are cost-effective catalysts, and they are herein benchmarked against the sulfonic acid resins Amberlyst-15 and Nafion®, and sulfonic acid-functionalized SBA-15...

Gamma-valerolactone (GVL) is a promising precursor for the preparation of biofuels and fuel-range hydrocarbons. This work shows the conceptual design of a process for the production of GVL from levulinic acid by means of catalytic transfer hydrogenation (CTH) over a bifunctional Zr−Al−Beta catalyst using an excess of isopropyl alcohol (IPA) acting...

The production of jet-fuel precursors from the aldol-dimerization of levulinic acid (LA) over acid zeolites is presented. Under solventless conditions, high LA conversion with selectivities to LA dimers >90% are achieved. Chemisorption and spectroscopic analyses of the materials have revealed a cooperative effect between strong Brønsted (BS) and st...

The feasibility of a Fenton-type process for the pretreatment of an oily refinery sludge has been explored taking advantage of the iron contained in the own sludge. This process reduces the content of total petroleum hydrocarbons (TPHs) accompanied by an increase in the total organic carbon concentration in the liquid phase. The effect of the tempe...

The EU's bioeconomy strategy has a strong commitment to the development of biotechnological approaches to convert municipal solid biowastes into value-added products. In this context, the current study investigated the thermophilic co-fermentation of pruning lignocellulosic and food wastes to co-produce hydrogen and carboxylic acids. Steam explosio...

An integrated method coupling of heterogeneous and biological catalysis has proven effective for producing biopolymers using lignocellulosic urban solid waste as feedstock. Catalysts based on cheap and earth-abundant metals, such as Fe, Mg, Ca, or Zr with basic or acid properties, were used in the pre-treatment step, and phototrophic mixed cultures...

Hospitals are one of the key contributors of pharmaceutical contaminants of emerging concern to the sewer systems. Hospitals wastewaters contain concentrations of pharmaceutical compounds between 3 and 150, which are higher than urban wastewater streams. However, dedicated treatments of the hospital effluents before discharge to the sewer system ar...

Purple phototrophic bacteria (PPB) showed an enormous potential for polyhydroxyalkanoates (PHA) production using the hydrolysate from lignocellulosic waste as feedstock. Thermal hydrolysis pretreatment was carried out at three different temperatures (120, 150 and 180 °C) aiming to improve the biodegradability of the lignocellulosic waste. After thi...

BACKGROUND Anaerobic treatments based on purple phototrophic bacteria (PPB) can be a more efficient and less energetic demanding alternative than current aerobic biological processes of refinery and petrochemistry wastewater (RPWW) treatment plants. Toxic compounds on the RPWW might compromise the PPB metabolism, limiting its feasibility. In this w...

Bioelectrochemical systems are a promising technology capable of reducing CO2 emissions , a renewable carbon source, using electroactive microorganisms for this purpose. Purple Pho-totrophic Bacteria (PPB) use their versatile metabolism to uptake external electrons from an electrode to fix CO2. In this work, the effect of the voltage (from −0.2 to...

Refinery treatment plants produce large quantities of oily sludge during the petroleum refining processes. The hazardousness associated with the disposal of these wastes, make necessary the development of innovative technologies to handle it adequately, linked to the concepts of circular economy and environmental sustainability. This work provides...

The increasing volume of waste streams require new biological technologies that can address pollution concerns while offering sustainable products. Purple phototrophic bacteria (PPB) are very versatile organisms that present a unique metabolism that allows them to adapt to a variety of environments, including the most complex waste streams. Their s...

The conventional Fenton process has been evaluated to treat highly furfural-containing wastewater of 76 g/L at an initial pH of 3. Streams of these features can be accidentally generated after solvent extraction operations in petrol refineries, which leads to significant concern for downstream wastewater treatment facilities. The influence of tempe...

Increased demand for effective waste management strategies, along with the need for a transition from a fossil fuel-based economy to a bio-based economy sharpens the need for synergies and scientific innovations. Food waste (FW) is an essential component of municipal solid waste, and its accumulation has become a global concern. This work discusses...

This study evaluates the influence of the presence of oxygenated groups created onto the surface of activated carbon (AC) on its ability to disperse platinum (Pt) or palladium (Pd) particles and on its catalytic performance to drive the transformation of glycerol into lactic acid. AC pretreatment consisted of oxidation in the presence of HNO3 aqueo...

Domestic wastewater treatment by purple phototrophic bacteria (PPB) is based on the assimilative uptake of organics and nutrients into the bacterial biomass. Thereby, it strongly depends on the carbon/nutrients ratio of the wastewater. The physiological COD/N/P ratio for PPB growth in domestic wastewater makes the addition of an external organic ca...

One of the current challenges in the treatment of wastewater is the recovery and/or transformation of their resources into high value-added products, such as biohydrogen. The aim of the present study was to optimize the production of hydrogen by mixed cultures of purple phototrophic bacteria (PPB), targeting in low CO 2 emission. Batch assays were...

The one-pot conversion of biomass-derived platform molecules such as levulinic acid (LA) and furfural (FAL) into γ-valerolactone (GVL) is challenging because of the need for adequate multi-functional catalysts and high-pressure gaseous hydrogen. As a more sustainable alternative, here we describe the transfer hydrogenation of LA to GVL using isopro...

The development of novel wastewater platforms should include the analysis of the most critical functional factors including the effects of toxic or inhibitory substances. Due to the novelty of purple phototrophic bacteria (PPB)-based wastewater treatment systems, this analysis has not been done yet in mixed cultures. In this work, various relevant...

Biomass, in its many forms—oils and fats, lignocellulose, algae, etc [...]

The sustainability of glucose production from two different feedstocks, maize starch (MS) and woody biomass residues (WBR), was evaluated by means of life cycle assessment (LCA) methodology. The aim of this work was to compare the environmental performance of conventional technology (glucose from MS by enzymatic hydrolysis) with a novel alternative...

In this study, two different organic fractions of municipal solid waste (OFMSW) served as raw material in a novel treatment process that combines thermal hydrolysis (TH) pretreatment at different times, followed by anaerobic digestion of the solid fraction and photo-fermentation of the liquid fraction. The results indicate that both wastes performe...

The direct one-pot transformation of glucose into γ-valerolactone (GVL) can be accomplished by means of a cascade of reactions in which Brønsted acid-catalyzed transformations are combined with catalytic transfer hydrogenation (CTH) by using 2-propanol as sacrificial alcohol, avoiding the use of high-pressure hydrogen. Catalysts containing Zr Lewis...

Sorbitol production from glucose was studied through catalytic transfer hydrogenation (CTH) over Raney nickel catalysts in alcohol media, used as solvents and hydrogen donors. It was found that alcohol sugars, sorbitol and mannitol, can be derived from two hydrogen transfer pathways, one produced involving the sacrificing alcohol as a hydrogen dono...

The hydrogenation of aqueous solutions of glucose into sorbitol has been tackled in the presence of ruthenium-functionalized catalysts using mesostructured pure-silica SBA-15 and ZrO2-coated SBA-15 materials as supports. The influence of the metal loading and the presence of ZrO2 in the supports on the catalytic activity of these materials have bee...

Improving the environmental performance of the industrial processes for the production of biomass-derived platform molecules is nowadays mandatory to achieve real sustainable bio-refineries. In this work, the sorbitol production starting from corn starch has been evaluated using a cradle-to-gate life cycle assessment (LCA) approach. The objective i...

The consumption and production of biodiesel has grown dramatically in recent decades, motivated by a strong interest in renewable energy. This has generated a surplus of its main by‐product, glycerol. Several catalytic processes have been proposed to generate alternatives for using this excess glycerol, mainly focusing on its transformation into hi...

Propagation of emerging pollutants (EPs) in wastewater treatment plants has become a warning sign, especially for novel resource-recovery concepts. The fate of EPs on purple phototrophic bacteria (PPB)-based systems has not yet been determined. This work analyzes the performance of a photo-anaerobic membrane bioreactor treating a low-N wastewater c...

Lactic acid and ester derivatives, important precursors of a wide variety of products, can be prepared via retro-aldol sugar condensation in the presence of Sn-containing zeolites. However, the preparation of such materials, often complex and requiring zeolitic structures difficult to obtain on a commercial scale, hinders the access of this technol...

The integration of GVL production in a lignocellulosic biorefinery where furfural and levulinic acid are co-produced is investigated in a one-pot process over Zr-Al-Beta bi-functional catalyst. Under the synthesis and reaction conditions previously optimized for the transformation of furfural, the yield to GVL for the different mixtures of levulini...

Raney nickel catalysts have been tested in the transformation of glucose into sorbitol through a hydrogen transfer pathway in the presence of short chain alcohols. Comparison between different sacrificing alcohols evidenced that catalytic hydrogen transfer (CHT) was only possible from ethanol under the tested neutral conditions. Catalytic tests sho...

Domestic and industrial wastewaters contain organic substrates and nutrients that can be recovered instead of being dissipated by emerging efficient technologies. The aim of this study was to promote bio-hydrogen production and carbon fixation using a mixed culture of purple phototrophic bacteria (PPB) that use infrared radiation in presence or abs...

Τhe coupling of biological with advanced oxidation processes for the removal of 13 pharmaceuticals is reported in this study. The efficiency of this system was examined by using two ligninolytic fungi, Trametes versicolor and Ganoderma lucidum. Pharmaceuticals’ removal was examined by using four different quinone substances (1,4-benzoquinone, 2,6-d...

Lignocellulosic residues from energy crops offer a high potential to recover bioproducts and biofuels that can be used as raw matter for agriculture activities within a circular economy framework. Anaerobic digestion (AD) is a well-stablished driver to convert these residues into energy and bioproducts. However, AD of lignocellulosic matter is slow...

Controlling the thickness of zirconia monolayers coated over SBA-15 offers an effective way to tune catalytic performance for the acid-mediated and hydrogen transfer (Meerwein Ponndorf Verley, MPV) cascade transformation of furfural to γ-valerolactone. Complementary mechanistic and kinetic modelling establishes the existence of the two distinct zir...

The optimization of the production of γ-valerolactone (GVL) from furfural (FAL) through a cascade of transformations involving hydrogen transfer and different acid-driven reactions has been tackled by using a bifunctional Zr-Al-beta zeolite as catalyst. The study involved the simultaneous evaluation of the influence of the main reaction parameters...

Micropollutants of emerging concern such as pharmaceuticals can significantly affect the performance of secondary biological processes in wastewater treatment plants. The present study is aimed to evaluate the toxicity and inhibition of three pharmaceutical compounds (caffeine, sulfamethoxazole and carbamazepine) on two cultures of microbial consor...

A wastewater coming from a pharmaceutical plant of chemical organic synthesis with a TOC of ca 1.4 g/L and low biodegradability has been treated by coupling of advanced Fenton oxidation process and subsequent biological treatment. The influence of the reaction temperature, the hydrogen peroxide concentration and the iron/copper loadings as catalyst...

The influence of Zero Valent Iron (ZVI) addition on the potential resource recovery during the anaerobic digestion (AD) of domestic waste sludge is assessed. Potentially recoverable resources analyzed were nutrients such as struvite to recover P, and energy as biogas to recover C. Short term (biochemical methane potential tests, BMP) and long term...

This article reviews the recent advances in the development of zeolite catalysts for biomass valorization processes to produce both biofuels and/or bio-based chemicals, which is an emerging and fast expanding field. The work deals with different types of feedstocks, including vegetable oils, lignocellulose and sugars, as well as with a number of re...

This chapter reviews briefly the principles of anaerobic digestion with special interest in innovative technologies to enhance the methane production. Biogas production from anaerobic digestion has been widely described in literature but this chapter wants to give a step forward focusing on two topics recently reported in literature and with specia...

The one-pot conversion of xylose into γ-gammavalerolactone in 2-propanol over bifunctional Zr-Al-Beta zeolites, prepared via a post-synthetic route, was optimized in terms of both catalyst synthesis and reaction conditions. In the catalyst preparation, the use of Zr(NO3)4 as zirconium source as well as the tuning of the amount of water used during...

The catalytic performance of two types of heterogeneous acid catalysts—sulfonic acid-functionalized materials and aluminum containing zeolites,—in the dehydration of sorbitol to isosorbide, in solventless and autogenous pressure conditions, has been studied. Catalysts screening evidenced strong differences between sulfonic acid-based materials and...

A series of bifunctional USY zeolite catalysts with different Al/Zr ratios were synthesised. The incorporation of Zr into the structure was accomplished after partial dealumination of H-USY. Structural and spectroscopic characterization confirmed the preservation of the zeolite network as well as the isolated incorporation of Zr atoms in Al vacanci...

SBA-15 materials were functionalized through a post-synthetic methodology with molybdenum-Schiff bases to provide catalytic activity in epoxidation reactions. Thus, glycidoxypropyl functionalities were first attached to the surface of the mesostructured silica, followed by the reaction of the immobilized oxirane groups with 2-amino propyl pyridine....

The objective of this study is to show the preliminary results of a (dynamic) mathematical model describing the effects of zero valent iron (ZVI) addition during the anaerobic digestion of waste activated sludge from wastewater treatment systems. A modified version of the Anaerobic Digestion Model No. 1 (ADM1) upgraded with an improved physico-chem...

This work investigates the biological treatment of synthetic wastewater contaminated with emerging pollutants (EPs) by anaerobic purple phototrophic bacteria (PPB) in a continuous photo-anaerobic membrane bioreactor. The effect of the hydraulic retention time (HRT) on the reactor performance has been analysed. Results indicate that the reactor perf...

The conversion of furfuryl alcohol, a highly versatile biomass-derived platform molecule, into a large variety of bio-products, including ethers, lactones and levulinates, has been evaluated in alcohol media using different solid acid catalysts, such as commercial zeolites, sulfonic acid-functionalized materials, and sulfated zirconia. Reaction pat...

In this chapter, we will highlight different chemical routes to convert highly functionalized sugars (glucose and xylose) coming from the hydrolysis of nonedible lignocellulosic biomass into high-energy-density biofuels with reduced oxygen content and improved H/C ratio. Firstly, this chapter will be focused on the chemical catalytic upgrading of l...

The effect of different oxidation processes at mild conditions including the coupled-Fenton (sono-Fenton, photo-Fenton and sono-photo-Fenton) and their blank systems (ultrasound, ultraviolet, zero valent iron and Fenton) on anaerobic digestion of the sludge for biogas production was investigated. Ultrasounds led to the highest organic matter solubi...

Propyl sulfonic acid functionalized mesostructured SBA-15 silicas have been used to promote the dehydration of sorbitol to isosorbide, in melted phase, under atmospheric pressure. These materials were prepared with different acid capacities and modified with different types of methylsilane functionalities, looking for an enhancement of the catalyti...

The one-pot conversion of xylose into GVL in 2-propanol has been achieved over bifunctional Zr- and Al-containing beta zeolite catalysts, prepared via a post-synthetic route, possessing both Brønsted and Lewis functionalities. A GVL yield of 35 mol% was obtained at 190 °C after 48 h.

Different solid acid catalysts, which include several zeolites, zirconium oxide based catalysts, and materials that contain sulfonic acids, have been evaluated in the dehydration of xylose to furfural in alcohol media. Alcohol media were selected to reduce side reactions, many of which occur in aqueous media. Among the tested alcohols, 2-propanol p...

Fe2O3/SiO2 materials were prepared using a simple sol-gel method and subsequent agglomeration to yield macroscopic particles of catalyst. The influence of silica source as well as the iron content in their physicochemical properties were studied and related with the catalytic performance and stability in a continuous intensified Fenton process. Lik...

The efficiency of two white-rot fungi (WRF), Trametes versicolor and Ganoderma lucidum, to eliminate thirteen pharmaceutical pollutants with concomitant biodiesel production from the accumulating lipid content after treatment, was examined. The removal efficiency was studied using both individual and combined strains. The results of individual and...

An integrated system based on a heterogeneous catalytic wet hydrogen peroxide oxidation (CWHPO) and subsequent rotating biological contactors (RBCs) has been modeled for the treatment of agrochemical wastewater. One dimensional pseudo-homogeneous model was proposed for the CWHPO step. The reaction rate for TOC removal (k1) was 0.087 1/min. In the c...

The use of sulfonic acid-functionalized heterogeneous catalysts in conjunction with the use of dimethyl sulfoxide (DMSO) as co-solvent in the catalytic transformation of fructose in ethanol to produce 5-ethoxymethyl furfural (EMF) is shown as an interesting alternative route for the production of this advanced biofuel. Arenesulfonic acid-modified S...

The zero-valent iron (ZVI)/H2O2 Fenton system can be considered as an effective solution for the removal of many of the organic pollutants present in the waste waters generated by the drug manufacturing industry. The hydrogen peroxide concentration and dosage rate were studied in order to improve the efficiency of the oxidant in the TOC reduction a...

The applicability of any wastewater technology should be related not only to its degradation, mineralization or detoxification efficiency, but also to its environmental impacts. This could be particularly relevant in case of Advanced Oxidation Processes (AOPs), which are usually highly demanding on chemicals, energy, and generating residual fluxes...

Zr-SBA-15 Lewis acid catalyst has demonstrated an outstanding catalytic activity in the reduction of several carbonyl compounds by means of Meerwein Ponndorf Verley (MPV) reaction, using several secondary alcohols, and showing a very high selectivity towards the desired products. Special focus was addressed in the catalytic activity of Zr-SBA-15 ma...