Combination of deep eutectic solvent and functionalized metal-organic frameworks as a green process for the production of 5-hydroxymethylfurfural and furfural from sugars.

Biomass is an abundant and sustainable resource that can be converted into energy and chemicals. Therefore, the development of efficient methods for the conversion of biomass into platform intermediates is crucial. In this study, the one-pot conversion of sugars into 5-hydroxymethylfurfural (HMF) and furfural was achieved using the metal-organic framework combined with metal ions [MIL-101(Cr)] as a high-activity catalyst, and a deep eutectic solvent (choline chloride and lactic acid) as a green solvent. The optimal temperature, time, amount of catalyst used, and amount of deep eutectic solvent used were all determined. The highest HMF yield of 49.74% and furfural yield of 55.90% were obtained. The recyclability of the catalysts and deep eutectic solvent was also investigated. After three reaction runs, the HMF yield was still nearly 30.00%. Finally, the MIL-101(Cr) catalytic system was selected to study the kinetic mechanism underlying the conversion of glucose into HMF.

Highly effective synthesis of 5-hydroxymethylfurfural from lignocellulosic biomass over a green and one-pot reaction in biphasic system.

In this study, different types of lignocellulosic biomas were used as substrates for the conversion to 5-HMF via biphasic reaction system that is composed of a reaction phase (aqueous phase) and an extraction phase (organic phase) under the catalysis of various metal salts. Deep eutectic solvents (DESs), ionic liquid [BMIM]Cl, aqueous choline chloride, aqueous betaine hydrochloride, and ethylamine hydrochloride were used as the reaction phase in the combination of dimethyl sulfoxide (DMSO) as organic solvents. The highest yields of 5-HMF obtained from pineapple stems in reactions with DES were 40.98%, 37.26%, and 23.44% for ChCl:Lac, ChCl:OA, and EaCl:Lac, respectively. Moreover, the combination of dimethyl sulfoxide, betaine hydrochloride aqueous solution, and AlCl3·6H2O with the pineapple stem conversion system resulted in a maximum yield of 61.04% ± 0.55% of 5-HMF. This study also demonstrated that AlCl3·6H2O and betaine hydrochloride could be effectively reused four times, which indicates a green and effective process.

Valorization of Glucose-Derived Humin as a Low-Cost, Green, Reusable Adsorbent for Dye Removal, and Modeling the Process.

Glucose can be isomerized into fructose and dehydrated into key platform biochemicals, following the "bio-refinery concept". However, this process generates black and intractable substances called humin, which possess a polymeric furanic-type structure. In this study, glucose-derived humin (GDH) was obtained by reacting D-glucose with an allylamine catalyst in a deep eutectic solvent medium, followed by a carbonization step. GDH was used as a low-cost, green, and reusable adsorbent for removing cationic methylene blue (MB) dye from water. The morphology of carbonized GDH differs from pristine GDH. The removal efficiencies of MB dye using pristine GDH and carbonized GDH were 52% and 97%, respectively. Temperature measurements indicated an exothermic process following pseudo-first-order kinetics, with adsorption behavior described by the Langmuir isotherm. The optimum parameters were predicted using the response surface methodology and found to be a reaction time of 600 min, an initial dye concentration of 50 ppm, and a GDH weight of 0.11 g with 98.7% desirability. The MB dye removal rate optimized through this model was 96.85%, which was in good agreement with the experimentally obtained value (92.49%). After 10 cycles, the MB removal rate remained above 80%, showcasing the potential for GDH reuse and cost-effective wastewater treatment.

Potential Application Performance of Hydrochar from Kitchen Waste: Effects of Salt, Oil, Moisture, and pH.

The surge in kitchen waste production is causing food-borne disease epidemics and is a public health threat worldwide. Additionally, the effectiveness of conventional treatment approaches may be hampered by KW's high moisture, salt, and oil content. Hydrothermal carbonization (HTC) is a promising new technology to convert waste biomass into environmentally beneficial derivatives. This study used simulated KW to determine the efficacy of hydrothermal derivatives (hydrochar) with different salt and oil content, pH value, and solid-liquid ratio for the removal of cadmium (Cd) from water and identify their high heating value (HHV). The findings revealed that the kitchen waste hydrochar (KWHC) yield decreased with increasing oil content. When the water content in the hydrothermal system increased by 90%, the yield of KWHC decreased by 65.85%. The adsorption capacity of KWHC remained stable at different salinities. The KWHC produced in the acidic environment increases the removal efficiency of KWHC for Cd. The raw material was effectively transformed into a maximum HHV (30.01 MJ/kg). HTC is an effective and secure method for the resource utilization of KW based on the adsorption capacity and combustion characteristic indices of KWHC.

Assessing the suitability of municipal sewage sludge and coconut bran as breeding medium for Oryza sativa L. seedlings and developing a standardized substrate.

The utilization of organic solid waste (OSW) for preparing standardized seedling substrates is a main challenge due to its temporal and spatial variability. This study aims to form models based on data from the literature and validate them through experiments to explore a standardized seedling substrate. The typical OSW in Hainan Province, including municipal sewage sludge (MSS), coconut bran (CB), seaweed mud (SM), and municipal sewage sludge biochar (MSSB), was used as raw material. A series of six mixing ratios was tested, namely: T1 (0% MSS: 90% CB), T2 (10% MSS: 80% CB), T3 (30% MSS: 60% CB), T4 (50% MSS: 40% CB), T5 (70% MSS: 20% CB), and T6 (90% MSS: 0% CB). SM and MSSB were added as amendment materials at 5% (w/w) for each treatment. The physicochemical properties of substrates, agronomic traits of rice seedlings and microbial diversity were analyzed. The results showed that the four kinds of OSW played an active role in providing rich sources of nutrients. The dry weight of the above-ground part was 2.98 times greater in T3 than that of the commercial substrate. Furthermore, the microbial analysis showed a higher abundance of Actinobacteria in T3, representing the stability of the composted products. Finally, the successful fitting of the results with the linear regression models could establish relationship equations between the physicochemical properties of the substrate and the growth characteristics of seedlings. The relevant parameters suitable for the growth of rice seedlings were as follows: pH (6.46-7.01), EC (less than 2.12 mS cm-1), DD (0.13-0.16 g cm-3), and TPS (65.68-82.73%). This study proposed relevant parameters and models for standardization of seedling substrate, which would contribute to ensuring the quality of seedlings and OSW resource utilization.

Influence of polyvinyl chloride microplastic on chromium uptake and toxicity in sweet potato.

The extensive use of plastic products and rapid industrialization have created a universal concern about microplastics (MPs). MPs can pose serious environmental risks when combined with heavy metals. However, current research on the combined effects of MPs and hexavalent chromium [Cr(VI)] on plants is insufficient. Herein, a 14-day hydroponic experiment was conducted to investigate the impact of PVC MPs (100 and 200 mg/L) and Cr(VI) (5, 10, and 20 µM) alone and in combination on sweet potato. Results showed that combined Cr(VI) and PVC MPs affected plant growth parameters significantly, but PVC MPs alone did not. The combined application of PVC MPs and Cr(VI) resulted in a decrease in plant height (24-65%), fresh biomass per plant (36-71%), and chlorophyll content (16-34%). Cr(VI) bioaccumulation increased with the increase in its doses, with the highest concentration of Cr(VI) in the leaves (16.45 mg/kg), stems (13.81 mg/kg), and roots (236.65 mg/kg). Cr(VI) and PVC MPs-induced inhibition varied with Cr(VI) and PVC MPs doses. Osmolytes and antioxidants, lipid peroxidation, and H2O2 contents were significantly increased, while antioxidant enzymes except CAT were decreased with increasing Cr(VI) concentration alone and mixed treatments. The presence of PVC MPs promoted Cr(VI) accumulation in sweet potato plants, which clearly showed severe toxic effects on their physio-biochemical characteristics, as indicated by a negative correlation between Cr(VI) concentration and these parameters. PVC MPs alone did not significantly inhibit these parameters. The findings of this study provide valuable implications for the proper management of PVC MPs and Cr(VI) in sweet potato plants.

Microwave-assisted deep eutectic solvents/dimethyl sulfoxide system for efficient valorization of sugar bagasse waste into platform chemicals: A biorefinery approach for circular bioeconomy.

The exploitation of lignocellulosic biomass (LB) such as sugar bagasse waste in biorefineries is the most cost-effective and favourable sustainable approach to producing essential platform chemicals, materials, and energy environmentally benignly. Herein, a microwave-mediated deep eutectic solvents (DESs)/dimethyl sulfoxide (DMSO) system for efficiently processing LB waste into platform chemicals was proposed thereof. Under optimized appropriate diverse parameters such as solvent varieties, catalyst dosage, DMSO addition, reaction time and temperature, the proposed catalytic system (i.e., microwave mediated DESs/DMSO system) has demonstrated significant yields of 5-hydroxymethylfurfural (5-HMF), furfural (FF) and levulinic acid (LevA) of 31.29 %, 28.38 % and 35.65 %, respectively. These favourable results were obtained at the reaction temperature of 140 °C for 40 min. The anticipated catalytic system's activation energy (Ea) was found to be 29.11 kJ/mol. Hence, a practical, inexpensive and sustainable process with the potential of high-value platform chemicals, explicitly for a sustainable strategy in a circular bioeconomy was proposed.

Synthesis of 5-hydroxymethylfurfural from glucose, fructose, cellulose and agricultural wastes over sulfur-doped peanut shell catalysts in ionic liquid.

In this study, waste peanut shells were sulfur-impregnated and used as acid catalysts in the presence of an ionic liquid for the conversion of fructose, glucose, and cellulose into 5-hydroxymethylfurfural, a useful chemical intermediate for biofuel production. Effects of sulfur-doping duration (1 h and 5 h), solvent type and proportion, reaction temperature (130 °C, 140 °C, and 150 °C), time (30-240 min), catalyst-to-substrate ratio (1-2.5 m/m), and agricultural residue (peanut shell, Canada wheat straw, water hyacinth, stalk, and reed) on HMF yields were investigated. Monophasic and biphasic ionic liquids such as [amim]Cl, [bmim]HSO4, and [emim]Cl were employed in combination with choline chloride and dimethyl sulfoxide to improve HMF yields. Results show that peanut shells subjected to prolonged sulfur impregnation produced higher HMF yields. At 130 °C and 2 h, HMF yields from fructose and glucose reached 94.6% and 55.1%, respectively. Higher reaction temperatures improved HMF yields and accelerated conversion rates for the sugar substrates. Moreover, HMF production from waste biomass namely, peanut shells, peanut stalk, Canadian wheat straw, reed, and water hyacinth were examined in separate one-pot catalytic reactions. Overall, the study showed the effectiveness of sulfur-doped peanut shells as solid acid catalysts for the synthesis of HMF from various sources and the results may be used in designing large-scale production of furanic biofuel precursors from agricultural wastes.

Removal of Isopropanol by synergistic non-thermal plasma and photocatalyst.

The dielectric barrier discharge (DBD) of non-thermal plasmas was combined with a self-made photocatalyst to remove isopropanol (IPA). Synthesis conditions for the novel photocatalyst, including calcination temperature and copper loading, were varied before photocatalysis to obtain at the optimal reaction efficiency. The effects of initial IPA concentration, oxygen content, and catalyst dosage were also observed. Finally, catalyst reusability was analyzed. X-ray photoelectron spectroscopy fitting revealed Ti, Cu, C, and O peaks in the synthesized catalyst. After a 60-min reaction with 100% oxygen as the carrying gas, nearly 100% of the IPA was converted. Overall, the optimal IPA conversion efficiency and acetone and carbon dioxide selectivity were achieved when the photocatalyst was synthesized at a calcination temperature of 550 °C and copper loading of 1.8%, along with a 100% oxygen carrying gas and a 3-mm discharge gap.

Influence of Chymosin on Physicochemical and Hydrolysis Characteristics of Casein Micelles and Individual Caseins.

The effects of chymosin on the physicochemical and hydrolysis characteristics of casein micelles and individual caseins were investigated. Adding 0.03 units of chymosin/mL led to the casein micelles in skim milk coagulating after a 3 h incubation period at 30 °C. SDS-PAGE investigation showed that ß-CN, κ-CN, αs-CN, and a portion of ß-lactoglobulin (ß-LG) in the milk supernatant fraction (MSF) were precipitated into the milk pellet fraction (MPF). The mean particle size of the MSF with chymosin decreased from 254.4 nm to 179.2 nm after a 3 h incubation period. Mass spectrometry and SDS-PAGE analysis suggested that chymosin hydrolyzed individual ß-CN, κ-CN, and αs-CN, but not ß-LG. Chymosin hydrolysis led to a decrease in the molecular weights of the hydrolyzed ß-CN, κ-CN, and αs-CN. Particle size analysis indicated that there was no difference in the particle size distribution of hydrolyzed ß-CN and αs-CN. Moreover, our outcomes demonstrated that the hydrolysis of κ-CN by chymosin occurs before that of ß-CN and αs-CN.

Interplays of enzyme, substrate, and surfactant on hydrolysis of native lignocellulosic biomass.

Tracking enzyme, substrate, and surfactant interactions to reach maximum reducing sugar production during enzymatic hydrolysis of plant biomass may provide a better understanding of factors that limit the lignocellulosic material degradation in native rice straw. In this study, enzymes (Cellic Ctec2 cellulase and Cellic Htec2 xylanase) and Triton X-100 (surfactant) were used as biocatalysts for cellulose and xylan degradation and as a lignin blocking agent, respectively. The response surface model (R2 = 0.99 and R2-adj = 0.97) indicated that Cellic Ctec2 cellulase (p < 0.0001) had significant impacts on reducing sugar production, whereas Cellic Htec2 xylanase and Triton X-100 had insignificant impacts on sugar yield. Although FTIR analysis suggested binding of Triton X-100 to lignin surfaces, the morphological observation by SEM revealed similar surface features (i.e., smooth surfaces with some pores) of rice straw irrespective of Triton X-100. The reducing sugar yields from substrate hydrolysis with or without the surfactant were comparable, suggesting similar exposure of polysaccharides accessible to the enzymes. The model analysis and chemical and structural evidence suggest that there would be no positive effects on enzymatic hydrolysis by blocking lignins with Triton X-100 if high lignin coverage exists in the substrate due to the limited availability of hydrolyzable polysaccharides.

Iron Modified Titanate Nanotube Arrays for Photoelectrochemical Removal of E. coli.

This study used iron modified titanate nanotube arrays (Fe/TNAs) to remove E. coli in a photoelectrochemical system. The Fe/TNAs was synthesized by the anodization method and followed by the square wave voltammetry electrochemical deposition (SWVE) method with ferric nitrate as the precursor. Fe/TNAs were characterized by SEM, XRD, XPS, and UV-vis DRS to investigate the surface properties and light absorption. As a result, the iron nanoparticles (NPs) were successfully deposited on the tubular structure of the TNAs, which showed the best light utilization. Moreover, the photoelectrochemical (PEC) properties of the Fe/TNAs were measured by current-light response and electrochemical impedance spectroscopy. The photocurrent of the Fe/TNAs-0.5 (3.5 mA/cm2) was higher than TNAs (2.0 mA/cm2) and electron lifetime of Fe/TNAs-0.5 (433.3 ms) were also longer than TNAs (290.3 ms). Compared to the photolytic (P), photocatalytic (PC), and electrochemical (EC) method, Fe/TNAs PEC showed the best removal efficiency for methyl orange degradation. Furthermore, the Fe/TNAs PEC system also performed better removal efficiency than that of photolysis method in E. coli degradation experiments.

Construction of a structural enzyme adsorption/kinetics model to elucidate additives associated lignin-cellulase interactions in complex bioconversion system.

Enzymatic hydrolysis is a rate-limiting process in lignocellulose biorefinery. The reaction involves complex enzyme-substrate and enzyme-lignin interactions in both liquid and solid phases, and has not been well characterized numerically. In this study, a kinetic model was developed to incorporate dynamic enzyme adsorption and product inhibition parameters into hydrolysis simulation. The enzyme adsorption coefficients obtained from Langmuir isotherm were fed dynamically into first-order kinetics for simulating the equilibrium enzyme adsorption in hydrolysis. A fractal and product inhibition kinetics was introduced and successfully applied to improve the simulation accuracy on adsorbed enzyme and glucose concentrations at different enzyme loadings, lignin contents, and in the presence of bovine serum albumin (BSA) and lysozyme. The model provided numerical proof quantifying the beneficial effects of both additives, which improved the hydrolysis rate by reducing the nonproductive adsorption of enzyme on lignin. The hydrolysis rate coefficient and fractal exponent both increased with increasing enzyme loadings, and lignin inhibition exhibited with increasing fractal exponent. Compared with BSA, the addition of lysozyme exhibited higher hydrolysis rates, which was reflected in the larger hydrolysis rate coefficients and smaller fractal exponents in the simulation. The model provides new insights to support process development, control, and optimization.

Conversion of rice husk into fermentable sugar and silica using acid-catalyzed ionic liquid pretreatment.

Rice husk is a bulky byproduct with a high silica content from rice milling. In this study, the application of an acid-catalyzed ionic liquid (IL) pretreatment was studied for processing rice husks with a rugged structure. The pretreatment conditions were 130°C for 30 min with 1.2 wt% HCl. The results of enzymatic hydrolysis demonstrated that cellulose conversion of HCl-BMIMCl-treated at 48 h was increased by 660.05%, 538.81%, and 376.55% compared with the untreated, HCl-treated, and BMIMCl-treated rice husks, respectively. Composition analysis demonstrated that most of the hemicellulose was removed in the acid-IL combined treatment. Moreover, scanning electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared analyses indicated that the crystalline structure and outer silica layer of the rice husks were efficiently broken up. The results revealed that the HCl-catalyzed dissolution is highly favorable for the industrial application of rick husks in the production of fermentable sugar and high-purity silica.

Gas-phase isopropanol degradation by nonthermal plasma combined with Mn-Cu/-Al2O3.

In this study, the dielectric barrier discharge (DBD) induced by nonthermal plasma (NTP) technology was used for isopropanol (IPA) degradation. IPA, intermediate, final product, and ozone concentrations were analyzed using GC-MS, carbon dioxide detector, and ozone detector. The experimental flow rate and concentration were fixed to 1 L/min and 1200 ppm ± 10%, respectively. Different reaction procedures were proposed for self-made metal catalyst combined with a plasma system (plasma alone and γ-Al2O3 combined with plasma, Cu (5 wt%)/γ-Al2O3 combined with plasma, Mn (3 wt%)-Cu (5 wt%)/γ-Al2O3 combined with plasma). In addition, the effect of the carrier gas oxygen content (0%, 20%, and 100%) on IPA conversion and intermediate and carbon dioxide selectivity was also investigated. The results revealed that the Mn (F)-Cu/γ-Al2O3 combined with plasma exhibited more efficient IPA conversion. In the 100% oxygen environment, the IPA conversion rate increased from 79.32 to 99.99%, and carbon dioxide selectivity increased from 3.82 to 50.23%. IPA was completely converted after 60 min of plasma treatment with the acetone selectivity, carbon dioxide selectivity, and tail ozone concentration of 26.71% ± 1.27%, 50.23% ± 0.56%, and 1761 ± 11 ppm, respectively. This study proved that the current single planar DBD configuration is an effective advanced treatment technology for the decomposition of VOCs.

Recycle of synthetic calcium fluoride and waste sulfuric acid to produce electronic grade hydrofluoric acid.

An innovative method for utilizing synthetic calcium fluoride (CaF2), recovered from fluoride-containing semiconductor wastewater, and waste sulfuric acid (H2SO4) to produce hydrofluoric acid (HF) was investigated. The research was set to study the low-temperature production of HF via reaction of synthetic CaF2 and waste H2SO4. The impact of four factors, including H2SO4 concentration, total volume (H2SO4 + H2O)/CaF2 ratio, drying temperature of synthetic CaF2, and reaction carried out under different temperature, on HF productivity was investigated in this study. HF yield increased with increasing H2SO4 concentration and total volume/CaF2 ratio under room temperature. Generally, reactions carried out under low-temperature (< 100 °C) had a positive impact on HF yield. The higher temperature led to an increase in absorbed-HF but a decrease in total-HF. The reaction of commercial CaF2 and 70% H2SO4 had a higher absorbed-HF yield of 61.7% than synthetic CaF2 and 70% waste H2SO4, which had a yield of 36%. This was due to the higher purity of the commercial CaF2 and fewer interference ions in H2SO4. HF productivity was lowered by CaSO4, which hindered the reaction of reactants and also the generation of fluorosulfuric acid.

Detecting phthalate esters in sludge particulates from wastewater treatment plants.

This study proposed a method for analysis of 10 phthalate esters compounds from wastewater treatment plant sludges. The analytical efficiency of GC-MS for of target compounds was verified by a standard mixture of phthalate esters. The response factors related to the respective internal standards from a five-point calibration curve quantified the phthalate esters in individual compounds. Based on the literature compiled by environmental agencies, new generation phthalate compounds have been developed, such as di-iso-nonyl phthalate (DiNP), di-iso-decyl phthalate (DiDP), as alternative to conventional phthalates. The analytical results showed that the total PAEs concentration was in the range from 7.4 to 138.6 mg kg-1 dw in these seven analyzed sludge samples. More, di-iso-nonyl phthalate (DiNP), di-iso-decyl phthalate (DiDP) and bis(2-ethylhexyl) phthalate (DEHP) contributed to over 99% of PAEs in the sludge. The correlation between total PAEs concentration in household and sewage flow treated at seven WWTPs and concentrations of DEHP, DiNP and DiDP was significant.

Degradation of trichloroethylene by photoelectrochemically activated persulfate.

Chlorine-containing organic compounds were discharged informally as a result of untreated industrial wastewater, which caused groundwater pollution. In this study, titanium dioxide nanotube arrays (TNAs) were modified with copper oxide to photoelectrochemical (PEC) active persulfate to degrade trichloroethylene (TCE). The SEM results show copper nano-particles with a cubic shape were successfully deposited on the surface of TNAs. The results of UV-vis analysis indicate the absorption wavelengths red-shift to 550-600 nm for better light utilization. CuO/TNAs were dominated by the anatase phase after sintering at 450 °C with significant visible light response. The chemical contents for the surface of CuO/TNAs are 23.7, 53.4, 18.4 and 4.4% for C, O, Ti and Cu, respectively. The photocurrent of CuO/TNAs is 1.89 times higher than that of TNAs-93 cm^2-1hr under 100 W Hg-lamp illuminations. This demonstrates the efficiency of light utilization of TNAs was improved by the modification with copper nanoparticles. The degradation rate of TCE in the anodic chamber is more effective than that in the cathodic chamber because of the synergistic effect of hydroxyl and sulfate radicals. The mechanism of TCE degradation via persulfate in the PEC system was proposed and discussed in detail.

Effect of microwave-assisted ionic liquid/acidic ionic liquid pretreatment on the morphology, structure, and enhanced delignification of rice straw.

In the present study, was investigated an environmentally friendly method for pretreating lignocellulosic rice straw (RS) by using 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) as an ionic liquid (IL) and 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO4) as an acidic-IL (Acidic-IL) under microwave irradiation (microwave-[Bmim]Cl and microwave-[Bmim]HSO4). The conversion of lignocellulosic biomass into simple sugars requires both efficient pretreatment and hydrolysis enzymes to produce biofuels and specialty chemicals. Therefore, the applied [Bmim]Cl, [Bmim]HSO4, microwave-[Bmim]Cl, and microwave-[Bmim]HSO4 to improve hydrolysis yields. Structural analyses of the pretreated solids were performed to understand the synergistic effects of [Bmim]Cl, and [Bmim]HSO4 pretreatment under microwave irradiation (microwave-[Bmim]Cl and microwave-[Bmim]HSO4) on the efficiencies of enzymatic hydrolyses. The results of a chemical composition analysis of untreated and all pretreated RS samples by using the difference pretreatment methods showed that significant lignin removal was achieved using microwave-[Bmim]Cl (57.02 ±â€¯1.24%), followed by [Bmim]Cl only (41.01 ±â€¯2.67%), microwave-[Bmim]HSO4 (20.77 ±â€¯1.79%), and [Bmim]HSO4-only (16.88 ±â€¯1.14%). The highest glucan yield and xylan conversion achieved through the enzymatic saccharification of microwave-[Bmim]Cl-regenerated cellulose was consistent with the observations obtained from a structural analysis, which indicated a more disrupted, amorphous structure, with lowered crystallinity index (CrI) and lateral order index (LOI) of cellulose polymers. Thus results demonstrated that the pretreatment of lignocellulosic biomass with [Bmim]Cl under microwave irradiation has potential as an alternative method for pretreating lignocellulosic materials.

High-concentration nitrogen removal coupling with bioelectric power generation by a self-sustaining algal-bacterial biocathode photo-bioelectrochemical system under daily light/dark cycle.

High-concentration nitrogen removal coupled with bioelectric power generation in an algal-bacterial biocathode photo-bioelectrochemical system (PBES) was investigated. The PBES can self-sustaining operation with continuous power output under day/night cycle by alternately using photosynthetic dissolved oxygen and nitrate/nitrite as cathodic electron acceptors. The PBES generated a high maximum power of 110mw/m2 under illumination and relatively lower power of 40mw/m2 under dark. The bioelectricity generation was accompanied by high-concentration nitrogen removal in the algal-bacterial biocathode. The NH4N was removed completely within 120 h while maximum NO3N removal efficiency of 86% and maximum total nitrogen removal efficiency of 83% can be reached after 192 h at initial NH4N concentration of 314 mg/L and NO3N concentration of 330 mg/L. Combined processes of bioelectrochemical reduction and algal-bacterial interactions provided multiple approaches for nitrogen removal in the biocathode, including nitrifying using photosynthetic oxygen, bioelectrochemical denitrification using the cathode as electron donor, heterotrophic denitrification using photosynthetically produced dissolved organic matters as carbon source and algal-bacterial uptake. Accelerated nitrogen removal with simultaneously improved cathode performance was observed at high concentration of nitrogen and phosphate buffer due to enhanced algal activities for photosynthetic oxygen release and enhanced algal-bacterial interactions for nitrogen transformation. Addition of external organic carbon negatively affected nitrification and decreased cathode potential due to oxygen consumption by aerobic carbon oxidation but enhanced denitrification due to continuous release of high concentration of photosynthetically produced dissolved organic matters by alga. The PBEC was demonstrated as an energy-saving approach for high-strengthen nitrogenous wastewater treatment.