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Effluent discharged from paper industries has an unfavourable impact on all the biotic and abiotic components of the environment due to the presence of various bio-recalcitrant toxic compounds. Multiple physico-chemical treatment systems have been adopted over the last two decades for the elimination of refractory organics from paper industry effluent but with limited success. Augmentation of biological treatment through metabolic and cometabolic strategies seems to be a promising and sustainable option. This article aims at presenting a comprehensive account of treating the paper industry effluent with existing treatment strategy using potent green agents through bioaugmentation and mineralization of chlorophenols via ortho- and meta- pathways. Sequential treatment based on consortia of specialized microorganisms remove > 90% of different toxic and recalcitrant compounds present in paper industry effluent. The rapid technological development in microbial fuel cells holds the potential for simultaneous paper industry effluent treatment and energy production.

Due to the rapid industrialization, heavy metals contamination in the aquatic environment has become more serious. Thus, it is urgent to develop enhanced removal technology for heavy metals. Graphene oxide (GO) based composite paper-like materials have been widely applied for adsorption of heavy metals from wastewater. Herein, we fabricated for the first time an advanced, highly-ordered and homogenous PVC/PPD/GO paper-like material using a resin-infiltration technique. This process is complimentary to layer-by-layer assembly, where the assembling components are required to interact strongly (e.g., via hydrogen bonding or electrostatic attraction). The results showed that the composite papers could achieve high removal efficiency of the heavy metals from water. The amount of Pb(II) adsorbed at equilibrium as achieved by GO, PVC/GO-0.05, PVC/GO-0.08, PVC/PPD/GO-0.05 and PVC/PPD/GO-0.08 buckypapers were 17.61, 22.17, 25.41, 33.57 and 44.80 mg g−1, respectively. In addition, the effects of experimental factors (e.g. GO content, ionic strength of heavy metal ions, temperature and solution pH) on heavy metal adsorption were discussed. Furthermore, the as-prepared PVC/PPD/GO-0.08 composite papers exhibited superior stability and could be recycled more than 900 h based on their 15 regeneration cycles. The improved heavy metal removal efficiency was attributed to the enhanced morphology and the formation of micro- and nano-channels created by the entangled PPD/GO. The findings indicated that the PVC/PPD/GO composite buckypapers could be used as promising materials for the adsorption of heavy metals from wastewater.

It is more and more urgent to develop low cost magnetic biochar for the removal of pollutants in water. In this study, magnetic biochar composites were prepared by one-step hydrothermal synthesis from sewage sludge and waterworks sludge (backwashing iron mud) and used to remove methylene blue (MB) from water. The synthesized samples were characterized by SEM, EDS, TEM, XRD, FTIR, XPS, VSM and BET. By changing the ratio of sludge and iron mud, three kinds of sludge-based magnetic biochar (SBMB) with good properties were successfully prepared. When the proportion of iron mud was higher, the samples were more magnetic, but when the proportion of sludge was higher, the adsorption capacity of the samples was greater. The magnetic materials in SBMB1, SBMB2 and SBMB3 were Fe3O4, and their saturated magnetization were 22.35 emu g−1, 45.16 emu g−1 and 53.56 emu g−1, respectively. SBMB had a good capacity for methylene blue removal and the process was rapid. In addition, SBMB had good magnetic properties, which can be easily separated from the solution by magnet after the experiment. The maximum adsorption capacities of SBMB1, SBMB2 and SBMB3 were 186.003 mg g−1, 178.786 mg g−1 and 164.316 mg g−1, respectively. In conclusion, this paper reports a simple and environmentally friendly method for the synthesis of magnetic biochar using sludge and iron mud as resources, which can provide a reasonable reference for the treatment of sewage sludge and backwashing iron mud in waterworks.

This study investigates the effect of the specially designed adsorptive packed column system (APCS) in improving the quality of biogas to biomethane purity. The APCS installed with the specially constructed “dispersal star” was operated on biogas from wastewater treatment plant. The four adsorbent packed columns were arranged based on two impregnated and two no-impregnated commercially available active carbons to remove siloxanes, halogenated compounds and volatile organic compounds. The removal performance of ACPS was tested using portable devices along with gas chromatography techniques coupled with different types of detectors. The removal efficiency of total non-silica impurities was obtained at the level of 99.76%, whereas siloxanes were removed entirely. The adsorption affinity of siloxanes in the shape of D4 and D5 was considered by adsorption on high BET surface area adsorbent, while the desulphurisation process was conducted on impregnated active carbons. This study describes the concentrations of silica and non-silica impurities in relation to CHP manufacturers’ limits and biomethane quality. Furthermore, the economical estimation of full-scale APCS was also conducted taking into account the three variants of biogas purity, as well as different types of iron-based adsorbents.

Dark fermentation (DF) systems usually exploit bioH2 production aiming to improve the energetic potential (EP) of anaerobic digestion (AD) schemes. In the case of sulfate-rich substrates, the versatility of fermentative consortia may favor the establishment of sulfidogenic conditions, minimizing/eliminating the competition between sulfate-reducing bacteria (SRB) and methanogens in the sequential stage and providing sulfide-free biogas. This study details the establishment of sulfidogenesis on the thermophilic DF of sugarcane vinasse in a continuous polyurethane-filled fixed-film reactor, also estimating the EP for vinasses according to different AD-related approaches. High sodium levels naturally stimulated SRB by maintaining high pH values (> 6.0), whilst NaHCO3 dosing was required when natural buffering conditions were not maintained. High acetate (~ 3 g-COD L−1) and COD/sulfate ratio (> 25.0) levels indicated a high-quality substrate for further methanogenesis. High butyrate concentrations (~11 g-COD L−1) coupled to caproate detection indicated the occurrence of chain elongation processes, leading to low bioH2 production levels (

To evaluate and approve the materials that can be in contact with drinking water with respect to biological contamination, organic carbon migration and biomass formation potential assays are widely employed. In previous studies, to conduct the assays, the entire material was exposed to the test water by submerging the material into glass jars. However, these are not realistic conditions since the water contact only the inner surface of the pipe in the distribution system, which may be different from the outer surface with respect to the coating layers. Furthermore, the extra components such as the glass jar containers and stainless steel holders might be the sources of organic carbon contamination. These two factors may result in imprecise conclusions. Here, we introduced a minor but essential modification to the BioMig test, which is the most current test on the migration potential and biomass formation potential. In this modified BioMig method, the outer surface and cutting edges, which are not in contact with water in practical water distribution systems, would not be exposed to the test water. Moreover, the assimilable organic carbon formation potential via chlorination in the leachates was observed and recommended as an additional test in the migration potential assay. The modified test results demonstrated that polyethylene (PE) material is the most unfavorable material, notably when used in chlorinated drinking water. This proposed test provided an alternative approach to the decision-makers with respect to evaluating the pipe material characteristics.

Anaerobic digestion (AD) can be a viable treatment option of organic wastes from restaurants, also generating biogas and digestate. Therefore, the aim of this work is to assess the treatment of organic residues from a university restaurant of Federal University of Santa Maria (UFSM). For this purpose, a 200 L semi-pilot scale anaerobic digester was monitored over 240 days, operating at mesophilic temperature in different hydraulic retention times (30 and 60 days). Substrate and digestate pH varied from 4.8 to 6.3 and 6.2–7.3, respectively. The average removal of chemical oxygen demand, biochemical oxygen demand, total solids, sedimentable solids, and volatile solids were 95%, 95%, 53%, 93%, and 77%, respectively. Biogas yield was 0.22 m3∙kg−1 VS or 67 L kg−1 of substrate with 60% of CH4 in average. Despite the variability in substrate composition, the results show high efficiency of the AD operation on decreasing the polluting potential of food waste, simultaneously generating both biogas and digestate, as a potential organic fertilizer. This work is a pioneer in the energy use of food waste from university restaurants in RS-Brazil, providing important information on AD operation, which can be useful in the design of a larger scale plant.

In this study, the production of fermentable sugars and biogas from thermally pretreated brewer’s spent grains (BSGs) was investigated. There were two autohydrolysis conditions (C1-1S: 180 oC, 30 min, 5 mLH2O gBSG−1 and C2-1S: 180 oC, 60 min, 5 mLH2O gBSG−1) which were evaluated, with and without a previous low severity pretreatment (80 oC, 10 min, 10 mLH2O gBSG−1). The highest specific methane production (302.4 NLCH4 kgCOD−1) and enzymatic hydrolysis yield (EHY of 98%, 50 FPU gBSG−1) were obtained from the two-stage pretreatment, with the second stage operated at 180 °C for 60 min, 5 mLH2O gBSG−1. However, in the integrated process, the two-stage pretreatment with the second stage performed at 180 °C for 30 min, and 5 mLH2O gBSG−1 was the best condition to produce fermentable sugars from enzymatic hydrolysis of pretreated BSGs, using a lower enzyme loading (EHY of 93%, 25 FPU gBSG−1). The burning of biogas produced from an anaerobic digestion of liquid fractions (hydrolysates) generated after two-stage thermal pretreatment in a combined heat and power system can produce a net thermal energy of 1.71 MJ kgBSG dry basis−1 and electrical energy of 0.392 kW h kgBSG dry basis−1.

Innovative removal of toxic nitrite and ammonia is one of the key approaches for efficient aquaculture biotechnology. This study suggests a fast removal technique of high-levels of nitrite and ammonia using recirculating aquaculture wastewater at 30‰ salinity. Four lab-scale moving bed biofilm reactors (MBBRs; R1, R2, R3, and R4) were operated in parallel for 56 days with different combinations of mature and fresh biofilms on biocarriers at 30% filling ratio. Nitrogen removal efficiency, biofilm physicochemical properties, and microbial analyses were conducted using PCR and sequencing techniques at the region of the 16S ribosomal RNA. The results showed that R4 (using mature biofilms) recorded the highest nitrite and ammonia removal (99.6% and 95.3%, respectively) compared to the control, R1 (94.1% and 89.4%). Meanwhile, the removal rate of ammonia in R4 was significantly the fastest compared to other reactors. Partial Least Squares-Discriminant Multivariate Analysis (PLS-DA) model showed a good prediction with very high accuracy and prediction (Q2 > 0.8) for the first three principal components pertaining to nitrite and ammonia removal. Planktosalinus genus was the most abundant in R4, while proteobacteria phylum was the dominant, followed by Marinobacter and Nitrospina in all reactors. Overall, the use of mature biofilms in MBBR was proven to increase bacterial diversity, enhancing nitrite and ammonia removal efficiency.

Microalgae have a high potential for the bioremediation of landfill leachate, mainly via nutrients removal, with the possibility of using the biomass for different purposes, depending on its characteristics. The present work aimed to evaluate the effect of hydraulic retention time (HRT) on the growth of microalgae in landfill leachate and on the composition of the biomass. Three photobioreactors (PBRs) with HRTs of 3, 6, and 10 days were used (PBRs 1, 2, and 3, respectively). Temperature, pH, ammonia nitrogen, total phosphorus, chemical oxygen demand, volatile suspended solids (VSS), and chlorophyll a (chl a) were monitored. The biochemical characterization of the biomass was carried out for lipids, carbohydrates, proteins, and ash. Chl a concentrations were 15.1 mg.L-1, 13.3 mg.L-1, and 4.9 mg.L-1 for PBRs 1, 2, and 3, respectively. For VSS, the concentrations were 130.4 mg.L-1 in PBR1, 149.1 mg.L-1 in PBR2, and 124.2 mg.L-1 in PBR3. The highest proportion of the biomass of the three reactors was protein, reaching 51.1% in PBR2. This result is justified by the high nitrogen concentration in the landfill leachate. The highest lipid accumulation occurred in PBR3, reaching 16.6%, due to the greater nutritional limitation imposed by the higher HRT. The results of this study provide important information for the use of HRT as an operational parameter for the production of algal biomass in landfill leachate, both in terms of productivity and biomass composition.

Anaerobic Membrane Bioreactors (AnMBRs) combine the advantages of anaerobic processes and MBR technology to improve effluent quality and energy recovery. However, these systems are associated with operational challenges such as membrane fouling and loss of dissolved methane that increases operation and energy expenses. In this study, a new configuration was developed combining AnMBRs with Microbial Electrolysis Cells (MECs). The effectiveness of the coupled AnFMBR-MEC system was tested by monitoring several indicators during the treatment of synthetic wastewater. The new configuration exhibited a 25-day shorter startup period, a 56% enhanced average methane yield, and a reduced membrane fouling with a maximum transmembrane pressure value nearly 6.5 folds lower than that exhibited by the AnFMBR alone. AnFMBR-MEC had an average CE of 40% and both reactors achieved around 90% COD removal. Similar bacterial communities existed in both reactors but with different relative abundance and localization. In the AnFMBR-MEC, the Direct Interspecies Electron Transfer was the likely dominant route for acetate consumption due to the abundance of Geobacter and Methanosarcina on the granular activated carbon and in suspension. The new system offers a promising technology with less fouling and improved resource recovery from wastewater due to the presence of different environmental niches (GAC, anode, cathode) for microbial colonization and growth, which resulted in the reduction of biomass in suspension and the proliferation of electroactive bacteria and methanogens as biofilms.

Bioleaching is an eco-friendly alternative for the extraction of metals from the spent fluid catalytic cracking catalyst (SFCCC). Acidothiobacillus ferrooxidans (A. ferrooxidans) are the most widely reported bacteria in leaching but remained unexplored for SFCCC till date. The present study proposes a cleaner, environmentally friendly process to leach metals from SFCCC by A. ferrooxidans. Batch bioleaching of metals was carried out with unadapted and adapted A. ferrooxidans. Experiments were performed by varying the pulp density (PD) (1–20%) at two different initial Fe(II) concentrations i.e. 2 g/L [M2Fe(II)] and 8.84 g/L [M8.84Fe(II)]. The results showed that adapted A. ferrooxidans leached out metals better than unadapted ones. Even though the loss of Iron to Jarosite formation was higher in M8.84Fe(II) than in M2Fe(II), leaching remained higher in M8.84Fe(II). Jarosite formation was minimized by maintaining the pH of the medium to 2 ± 0.1. Maximum leaching efficiency was observed at 1% PD. At this concentration. A. ferrooxidans growth was triggered which increased the production of Fe(III), thereby increasing leaching efficiency. Increase in PD led to a decrease in metal leaching efficiency. The maximum leaching observed by A. ferrooxidans is Al (35%), Ti (14%), Ni (27%) and V (56.5%). The amount of Al leached (70 mg/gm of SFCCC) suggests SFCCC be the potential secondary source of Al compared to popular secondary sources such as red mud and other spent catalysts. Al and V were better leached by A. ferrooxidans while organic acids were more suitable to extract Ti and Ni from SFCCC.

The need for wastewater treatment does not only arise from an environmental conservation point of view. But also, from the fact that it can be reused for secondary proposes. The most of hospitals being present in urban space, still their wastewater treatment are not fully explored. The Fluidized Aerobic Bed Bioreactor (FABB) treats wastewater in a liquid-solid phase among various wastewater treatment processes. This study employed a fluidized aerobic bed reactor coupled with a tube settler for hospital wastewater treatment. The treatment efficiency was evaluated based on the removal of pollutants and nutrients with associated parameters pH, Alkalinity, total suspended solids (TSS), and mixed liquor suspended solids (MLSS). The efficiency was determined by evaluating the influent and effluent quality of samples. The BOD5 was reduced at an average of 69% in FABB, and for tubesettler, it resulted in consumption of only 39%. Similar types of results were obtained when considering it for COD, i.e., 72% and 38%, respectively, for FABB and tube settler. The nitrification was observed in both nitrate accumulation by 103% and 3.65% in FABB and tube settler. In the absence of anaerobic conditions, the denitrification process could not be achieved. Hence the cycle was not completed. Lower phosphate reduction was achieved, 63% and 23%, however concentration in influent were below the permissible limit of 5 mgL−1. The study concludes that FABB can be successfully employed for hospital wastewater treatment. Additionally, tubesettler may be used in place of a secondary clarifier in the treatment of hospital wastewater.

More sustainable processes capable to minimize the demand for chemical inputs and the generation of toxic wastes are essential to scale up the pretreatment strategies applied to lignocellulosic biomass for bioenergy production. This study aimed to evaluate the reuse of the black liquor (hydrolysate) generated after alkaline pretreatment as a sustainable and cheaper strategy to increase biodegradability of grass clippings (GC) and enhance process economic feasibility. Batch anaerobic digestion experiments were carried out at mesophilic temperature (37 °C) using KOH and NaOH solutions at a concentration of 5% (w/v). The methane yield of the untreated substrate was 227 LN CH4 kg−1 VS. Methane yields obtained from pretreated grass clippings using KOH and NaOH at 5% were increased to 30.5% and 34.5% and the hydrolysate generated after the pretreatments showed statistical (p

Incorporation of zinc oxide (ZnO) nanoparticles has played an important role on the improvement of unique membrane characterization and performance, most notably the hydrophilic modification of the membrane for higher pure water permeability. Additionally, the permeability of the membrane can be improved via introduction of braid support by reducing the thickness of the membrane separation layer. Moreover, the braided hollow fiber membrane (BHFM) is able to perform under higher pressure conditions compared to hollow fiber membranes. In this paper, hybrid polysulfone (PSf)/ZnO BHFMs were fabricated via phase inversion method. Hydrophilic 10 ± 1.8 nm polycrystalline ZnO nanoparticles synthesized via sol-gel method were incorporated on BHFM to improve the hydrophilicity and increase flux with constant rejection under high pressure and the effect of the ZnO loading on the membrane properties and performance were thoroughly studied. The fabricated BHFMs with 0.0, 0.5, 1.0 and 1.5 wt% of ZnO nanoparticles concentration were defined as BHFM1, BHFM2, BHFM3 and BHFM4 respectively. Scanning electron microscopy (SEM), contact angle, mechanical strength, flux performance, rejection with bovine serum albumin (BSA) and fouling of best performed membrane were conducted to achieve the target of this paper. The performance of these hybrid ZnO/PSf BHFMs were compared with neat PSf hollow fiber membrane (HFM) and previous studies. The findings from this research work shows that BHFM4 has the most desired properties for wastewater treatment application. The ZnO nanoparticles in BHFM4 have improved hydrophilicity from 108.79° to 71.02°, and thus BHFM4 has increased flux performance from 36.20 to 919.12 L/m2 h at 1.0 bar pressure and 193.48 to 1909.11 L/m2h at 4.0 bar pressure when compared with BHFM1. Constant BSA rejection rates (> 90%) were observed in all BHFMs. The improved hydrophilicity and pure flux performance with constant rejection rate in high pressure conditions illustrates the suitability of fabricated ZnO/PSf BHFMs in wastewater treatment applications.

Sintered glass filters are used in chemical plants and laboratories to separate particulate matter from liquids. This paper reports their hydrophobic modification to render an additional function: the separation of water-immiscible organic liquids (oils) from water as well as emulsified water. To coat the filters, chlorodimethyloctadecylsilane and a 5 kDa poly(dimethyl siloxane) sample bearing an epoxy end group, PDMS-Ep, are covalently grafted onto the filter pore walls. Investigated are how varying the hydrophobic coating agent, its solution concentration, water content in the emulsion, and the filter pore size affects oil separation. While the oil flux increases with the filter pore size and pressure drop across the filter, the tilting of a filter from its horizontal position or the stirring of the feed emulsion also increases the separation flux presumably due to reduced pore blockage by the settling water. Based on the knowledge gained through this study, a prototype funnel for the household purification of wet gasoline is constructed. Such a funnel is shown to completely remove water droplets from wet gasoline, which contrasts with the inadequate performance of a commercial funnel sold specifically for this application. The developed filter should have applications in the treatment of wet gasoline and in the separation of organic phases from water in chemical laboratories and plants.

In recent years, low-cost and eco-friendly biomass materials have become the focus of research for the purposes of removing poisonous noble metals waste. In particular, the role of walnut shell biomass material in the adsorption of heavy metals has garnered significant attention, an example being the boron-nitrogen co-doped walnut shell biochar powder (B-N-WSBP) which can be synthesized through one-step pyrolysis process. Various methods and analyses, including scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), Raman spectroscopy (Raman), Brunauer-Emmett-Teller specific surface area analysis (BET), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA), were used to characterize the morphology, structure, and physical properties of prepared B-N-WSBP. In this paper, different experimental conditions affecting adsorption including adsorption dose, solution pH, ionic strength , time, and temperature were investigated. Experimental results showed the B-N-WSBP achieved maximum adsorption rates of Au(III), Pt(IV), and Pd(II) of 246.96 mg g−1, 108.8 mg g−1, and 44.78 mg g−1, respectively. The results further suggested that the adsorption kinetics are combined with a quasi-two-stage kinetic model. The adsorption isotherm equilibrium data were aligned with the Langmuir isotherm model, which indicated that the mechanism of reaction between B-N-WSBP and the noble metal ions belongs to chemical and single-layer adsorption.

In this study, a novel technology for the co-treatment of spent automotive catalyst (SAC) and cyanide tailing (CT) was proposed. The mixed waste material of SAC and CT were subjected to carbon thermal reduction-smelting with the addition of flux of CaO and Na2B4O7. The platinum group metals (PGMs)-containing iron alloy (Fe-PGMs alloy) and the non-hazardous glass slag were successfully obtained. The optimum conditions for this technology are that the addition of CT, addition of reducing agent, addition of Na2B4O7, basicity, smelting temperature, and holding time for PGMs recovery rate was 30 wt%, 12 wt%, 5 wt%, 0.7–0.8, 1550 °C, and 60 min, respectively. Under these conditions, over 99% of PGMs can be recovered from the mixed waste materials and the content in the produced glass slag was below 5 g/t. Meanwhile, the total Fe content in obtained Fe-PGMs alloy was approximately 85% and its recovery was up to 90%. Furthermore, the mechanism was discussed, which can be divided into three processes: reduction and melting, migration and collection, and alloy formation. Besides, the results of the toxicity characteristics of glass slag indicated that heavy metal and the metalloid of arsenic (As) in the produced glass slag were successfully immobilized, which confirmed the produced glass slag can be taken as non-hazardous slag. Therefore, the co-treatment approach of SAC and CT proposed in this paper is an economical and environmentally friendly technology to recover the PGMs from SAC.

High-concentration formaldehyde-based wastewater causes a serious hazard to the human body and ecosystem. Electro-Fenton technology can be used for the pre-treatment of high-concentration formaldehyde wastewater, but the uneven distribution of free radicals and formaldehyde affects the degradation efficiency of Electro-Fenton. Oxygen-containing functional groups can enhance the adsorption and enrichment of the pollutants near the cathode, thereby improving the degradation efficiency of Electro-Fenton. In this paper, quantum chemical simulation was adopted to study the effects of different oxygen-containing functional groups on the adsorption of formaldehyde on the carbon surface. The results showed that incorporating oxygen-containing functional groups changed the electronic structure of the carbon surface and affected the interactions between formaldehyde and carbon surface. Only the incorporation of certain oxygen-containing functional groups at the edge of the carbon surface could promote the adsorption of formaldehyde. Edge ether group promoted the basal plane adsorption of formaldehyde on the carbon surface by enhancing dispersion interactions. The edge carboxyl group and edge hydroxyl group influenced the edge adsorption of formaldehyde on carbon surface due to the enhancement of electrostatic interactions. The edge pyrone group promoted the edge adsorption of formaldehyde by influencing the dispersion interactions and electrostatic interactions between formaldehyde and the carbon surface.

Ballast water is an essential component of nautical navigation, however, the microorganisms present in the water may be an environmental hazard. Therefore, the decontamination of ballast water has been widely studied. The anchoring of metal nanoparticles with plasmonic properties into semiconductors is an effective way to enhance their photocatalytic activity for the inactivation of marine microorganisms in ballast water. In this paper, we describe the successful synthesis of BiQDs/BiVO4 via a facile solvothermal method and evaluated their capacity to inactivate marine microorganisms under visible light irradiation. The results showed that 3%BiQDs/BiVO4 exhibited greatest photocatalytic sterilization efficiency with the low concentration of H2O2 present in real seawater. Further results revealed that the BiQDs had a diameter of approximately 5.1 nm and were distributed randomly on BiVO4, and that the SPR effect of BiQDs enhanced the utilization of visible light. The hydroxyl radical was proven to be the main active species and the addition of H2O2 promoted the generation of ·OH to achieve the efficient decontamination of ballast water. This study may provide a potential route for the photocatalytic removal of marine microorganisms and ballast water tank protection.

Over the years, algae have found wide scope of utility in a variety of environmentally beneficial processes like biofuel production, removal of heavy metals from wastewater sources for potential bioremediation, monitoring water pollution and source of animal nutrition. However, the conventional harvesting methods pose a set-back in terms of energy, cost and operational complications due to the small size of microalgae. Of all the processes, harvesting alone corresponds to approximately 30% of the total production costs. Recent advancements in the microalgal technology have brought many efficient techniques into use for improved recovery of microalgae. This review comprehends the development, principle, influencing parameters and directions to future research of one of the state-of-the-art approaches for harvesting microalgae, electrochemical technology. Though this area was previously explored for its application in wastewater treatment, it has lately gained momentum in the field of microalgae due to its economic efficiency. This paper highlights the three prime processes used to yield microalgae namely electroflocculation, electroflotation and a combined electrocoagulation-flotation (ECF) system. Several encroachments and strategies among these techniques have also been elucidated. The review focusses on the effect of most significant process controlling parameters such as reactor and electrode design, various surface properties of microalgae, current, pH, salinity and agitation that influence harvesting. In addition, the economy and energy aspects that emphasize the welfares of this technology over others have been extensively discussed. The overall work aims to provide an insight into the electrochemical methods, their challenges and opportunities that might be beneficial for carrying out further research and scope for industrial applications.

This study examines the feasibility of the use of nanocomposite of polyaniline (PAni) grafted sulfonated graphene oxide (SGO) supported manganese cobalt oxide as a novel and effective cathode catalyst for single chamber microbial fuel cell (SC-MFC). The graphene oxide (GO) was sulfonated to SGO for the development of a significant increase in the hydrophilicity of GO to enhance the nano−catalyst dispersion. The structural properties of the prepared nanocomposite were studied by X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. Morphological studies of the nanocomposite revealed a wrinkled paper−like structure of SGO and a spherical type structure of Mn−Co. Both cyclic voltammetry and electrochemical impedance spectroscopy showed a reduction current value of −1.04 mA, and charge-transfer resistance of 52.4 ohm, which exhibited a higher oxygen reduction reaction activity and good conductivity compared to Mn−Co/GO−PAni, Mn−Co/rGO−PAni and Pt/C catalyst. Electrochemical tests also suggest that the Mn−Co/SGO−PAni nanocomposite exhibited excellent durability among the other three cathodes. Furthermore, the MFCs equipped with Mn−Co/SGO−PAni nanocomposite modified electrode achieved power density of 1392.68 mW m−2 which is 2.89 times higher than state-of-art Pt/C (481.3 mWm−2). The Electrochemical studies also displayed a similar result. The significant increase in power generation with Mn−Co/SGO−PAni nanocomposite as a cathode catalyst indicates that it can be used as a promising, inexpensive electrocatalyst for the long-term operation for MFC.

This paper aims to explore the possibility of using spent carbon anode residue (SCA) from aluminum electrolysis as anode materials for lithium-ion batteries. SCA of hazardous solid waste is recovered by a two-stage process of “chemical leaching–high-temperature graphitization” to achieve harmlessness and resource treatment. Chemical leaching can increase the carbon purity of SCA-CL from 61.86% to 92.80% and cause the formation of surface holes-defects structure, which serves to shorten the Li+ transmission distance. High-temperature graphitization can increase the carbon purity of SCA‐CL‐2800 to 99.90% and cause the significant graphite sheet structure, which can increase the conductivity. SCA-CL-2800, used as the anode material for Li-ion batteries, showed the first capacity of 359.1 mAh g−1 at 0.1 C, the initial coulombic efficiencies of 80.17% and a reversible capacity of 368.6 mAh g−1 after 50 cycles. Compared with graphite, SCA-CL-2800 exhibited excellent electrochemical performance. It is estimated that the preparation method provides an innovative strategy for recovery and application of similar solid waste.

Recovering Cr(III) from chromium-containing waste (CCW) is considered to be a friendly way to protect environment. In this paper, the recovery of Cr(III) from CCW is achieved, via alkali incineration (NaOH and Na2CO3), followed with leaching process using HCl. Firstly, it is demonstrated that there is a large amount of organic matters (oxygen-containing functional groups contained in collagen) in CCW, charactering with Infrared spectrophotometry (FT-IR), Thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Furthermore, density functional theory (DFT) simulation method is carried out to study the inhibitory behavior of organic matters on recovery of Cr(III). Through geometric optimization, binding energy calculation and a series of electronic structure analysis, the influence of organic matters are analyzed in detail. According to the calculation results, it is clarified that the inhibition mechanism of organic matters on Cr(III) is mainly contributing by forming covalent bond and -OH exhibits greater inhibiting effect than -COOH. In this examine, the related factors are also investigated to reduce the amount of organic matters that is destroyed, including extractant species, alkali dosage, acid dosage and acid concentrations. Finally, the recovering efficiency of Cr(III) is greatly enhanced (95.83%), associated with optimized factors in the process.

Copper nanoparticles (CuNPs) impregnated biocomposites (Cu/chit-NBC) were prepared and characterized by the state-of-the-art analytical techniques. The CuNPs were in the average size ranges of 45.6–63.7 nm and 86.4 nm as confirmed by scanning electron microscopy and dynamic light scattering, respectively. To decolorize the crystal violet from the aqueous medium, fabricated Cu/chit-NBC was applied as an adsorbent. Box–Behnken design using three independent variables was adopted to optimize the Crystal Violet (CV) decolorization process. Under the optimum conditions of temperature 42.7 °C, pH 9.5, and 149.9 mg L−1 dose of adsorbent, 99.7 ± 0.2% decolorization was observed. Cu/chit-NBC also showed a very high dye removal capacity in simulated industrial textile effluents of around 99.7 ± 0.2%. The CV decolorization was consistent with pseudo-second-order kinetics and best fitted with the Freundlich adsorption isotherm. The nature and the potential processes involved in interactions between the CV and the nano-bioadsorbents during discoloration have been discussed in this paper.

Energy and the environment has long been a topic of concern. Activated carbon (AC) is a widely used high-performance industrial material. Agricultural and forestry waste (AFW) is a sustainable and economical resource for AC production. In the field of AFW-derived AC (AFWAC) research, the characteristics of the pore structure are important indicators of the quality and possible applications of AFWAC. Therefore, it is of great significance to conduct in-depth studies on the factors affecting the pore structure in the preparation process of AFWAC, and to control and predict the properties and extent of the pore structure of AFWAC during the preparation so its performance can also be controlled. In this paper, various preparation methods and condition parameters of AFWAC are reviewed, including carbonization and activation methods, and the effects of AFW types, activator types, activator amount, activation temperature, and activation time on the pore structure of AFWAC are discussed in detail. Second, other properties and an economic analysis of AFWAC are carried out. Finally, the specific application of AFWAC with different pore structure characteristics in gas and liquid phase adsorption is expounded. This review promotes the research of AFWAC and its real-world applications by optimizing different preparation methods and conditions to effectively obtain high-performance, low-cost, and targeted AFWACs suitable for different applications.

Molybdenum disulphide (MoS2) is a transition metal dichalcogenide most widely studied as a heterogeneous catalyst due to its outstanding structural and physicochemical properties. Today, 2D layered MoS2 has gained much attention due to its variety of environmental remediation applications, production of cleaner fuels, and energy storage. MoS2 is a structural analogue of graphene and has similar properties, like greater surface area, a good charge carrying capacity, and higher mechanical strength. Therefore, MoS2 can be easily coupled with graphene to further enhancing its catalytic efficiencies. Moreover, MoS2 is less costly, highly abundant, has better light absorption capacity and adjustable bandgap than graphene. Most of the recent advancements in structural and synthesis techniques for improving catalytic properties of MoS2 for various applications like photodegradation of dyes and organic compounds, hydrogen production, dye-sensitized solar cells, electrochemical capacitors, hydrodesulfurization, chemical and biological sensors, and gas sensors are discussed in this paper. Future prospective and research topics for the development of MoS2 based composites are also discussed.

Much attention has been focused on the synthesis of TiO2 based materials as photocatalysts for water pollutant treatment, it still needs overcome difficulties of separation of TiO2 photocatalyst from the treated water and the recombination of photo-induced carriers to improve catalytic activities. In this paper, a magnetical core-shell Fe3O4@SiO2@Sn-TiO2 (FST-S) composite photocatalyst was designed and prepared via prepared via Stober and sol-gel methods. The effect of Sn2+ coating TiO2 on the surface of Fe3O4@SiO2 nanoparticles was principally investigated. The photocatalytic performance and recyclability of FST-S were evaluated by photodegradation of tetracycline hydrochloride (TC). Experimental results show that Sn2+ doping increased the content of TiO2 in composite photocatalyst. Because some Sn2+ ions lead to the decrease in the stability of Sn2+-TiO2 nanoparticles and then low-stable Sn2+-TiO2 nanoparticles enter into the composite photocatalyst by condensation with the Sn2+-TiO2 outer shells of FST-S. The photodegradation results show that FST-S sample exhibits an outstanding photocatalytic capacity with a superior degradation rate of 98.2% within 40 min and a good reusability without significant decrease of activity after reused for six cycles. The reaction rate constant (k) of the FST-S was 3.86 times compared with that of without Sn doping Fe3O4@SiO2@Sn (FST). Reactive species scavenging experiments revealed that O2-• it plays a dominant role in photodegradation process. The distinct enhancement of photocatalytic activity of Fe3O4@SiO2@Sn-TiO2 is mainly ascribed to the high amount of TiO2 and low recombination rate of photogenerated electron-holes. This work initiates a novel strategy to prepare magnetical core-shell photocatalysts with excellent activity.