Simulated Industrial Wastewater Research Articles

Thermally Enhanced Relay Electrocatalysis of Nitrate-to-Ammonia Reduction over Single-Atom-Alloy Oxides.

The electrochemical nitrate reduction reaction (NO3RR) holds promise for converting nitrogenous pollutants to valuable ammonia products. However, conventional electrocatalysis faces challenges in effectively driving the complex eight-electron and nine-proton transfer process of the NO3RR while also competing with the hydrogen evolution reaction. In this study, we present the thermally enhanced electrocatalysis of nitrate-to-ammonia conversion over nickel-modified copper oxide single-atom alloy oxide nanowires. The catalyst demonstrates improved ammonia production performance with a Faradaic efficiency of approximately 80% and a yield rate of 9.7 mg h-1 cm-2 at +0.1 V versus a reversible hydrogen electrode at elevated cell temperatures. In addition, this thermally enhanced electrocatalysis system displays impressive stability, interference resistance, and favorable energy consumption and greenhouse gas emissions for the simulated industrial wastewater treatment. Complementary in situ analyses confirm that the significantly superior relay of active hydrogen species formed at Ni sites facilitates the thermal-field-coupled electrocatalysis of Cu surface-adsorbed *NOx hydrogenation. Theoretical calculations further support the thermodynamic and kinetic feasibility of the relay catalysis mechanism for the NO3RR over the Ni1Cu model catalyst. This study introduces a conceptual thermal-electrochemistry approach for the synergistic regulation of complex catalytic processes, highlighting the potential of multifield-coupled catalysis to advance sustainable-energy-powered chemical synthesis technologies.

The Optimization of Hydrodynamic Cavitation as an Advanced Oxidation Option for the Removal of Persistent Contaminants in Wastewater

Wastewater is increasingly becoming the primary source of potable water in many cities, thanks to the development of recycling facilities. Persistent contaminants such as dyes and perfluorinated compounds from textile industries as well as other contaminants necessitate the design of removal technologies to treat wastewater to reduce these chemicals before discharge or being used as feed to a potable water plant. Several chemical treatment techniques have been reported but the most utilized advanced chemical treatments lead to high costs and further environmental concerns. This study investigated an alternative approach to wastewater treatment using a hydrodynamic cavitation pilot plant combined with a venturi as a way to remove recalcitrant compounds. The optimization of the removal process was explored by testing the effect of orifices with size 2, 3, 4, 5, or 6 mm on the decoloration of orange II dye. The impact of the catalyst: iron(II); oxidizing agent: hydrogen peroxide; and contact time was evaluated to find the ideal conditions under which the removal of perfluorooctanoic acid (PFOA) could be achieved. The decoloration of 20 ppm of orange II dye in simulated industrial textile wastewater was achieved at 90% efficiency when the pressure at the inlet was maintained at 300 kPa, the temperature at 34 °C, the pH at 2, and the orifice size at 2 mm of diameter. The kinetic study proved the decoloration reaction was pseudo first order and the rate of decolourisation of orange II was 0.23/min.Ten parts per million of PFOA could not be degraded by free radical attack using advanced oxidation processes when the inlet pressure was maintained at 300 kPa, the temperature at 34 °C, the pH of 2, and the orifice diameter of 2 mm. This resistance to removal is due to the structure of PFOA which is made up of a fluorine ion which stabilizes the compounds by inductive effects while dye is made up of nitrogen ion and is compatible with the above removal methods. The study demonstrated that the combination of venturi and orifice requires the throat size of the venturi to be similar or equal to that of the orifice for better efficiency.

Multi‐Functional Formaldehyde‐Nitrate Batteries for Wastewater Refining, Electricity Generation, and Production of Ammonia and Formate

AbstractAs bulky pollutants in industrial and agricultural wastewater, nitrate and formaldehyde pose serious threats to the human health and ecosystem. Current purification technologies including chemical and bio‐/photo‐/electro‐chemical methods, are generally high‐cost, time‐consuming, or energy‐intensive. Here, we report a novel formaldehyde‐nitrate battery by pairing anodic formaldehyde oxidation with cathodic nitrate reduction, which simultaneously enables wastewater purification, electricity generation, and the production of high‐value‐added ammonia and formate. As a result, the formaldehyde‐nitrate battery remarkably exhibits an open‐circuit voltage of 0.75 V, a peak power density of 3.38 mW cm−2 and the yield rates of 32.7 mg h−1 cm−2 for ammonia and 889.4 mg h−1 cm−2 for formate. In a large‐scale formaldehyde‐nitrate battery (25 cm2), 99.9 % of nitrate and 99.8 % of formaldehyde are removed from simulated industrial wastewater and the electricity of 2.03 W⋅h per day is generated. Moreover, the design of such a multi‐functional battery is universally applicable to the coupling of NO3− or NO2− reduction with various aldehyde oxidization, paving a new avenue for wastewater purification and chemical manufacturing.

Multi-Functional Formaldehyde-Nitrate Batteries for Wastewater Refining, Electricity Generation, and Production of Ammonia and Formate.

As bulky pollutants in industrial and agricultural wastewater, nitrate and formaldehyde pose serious threats to the human health and ecosystem. Current purification technologies including chemical and bio-/photo-/electro-chemical methods, are generally high-cost, time-consuming, or energy-intensive. Here, we report a novel formaldehyde-nitrate battery by pairing anodic formaldehyde oxidation with cathodic nitrate reduction, which simultaneously enables wastewater purification, electricity generation, and the production of high-value-added ammonia and formate. As a result, the formaldehyde-nitrate battery remarkably exhibits an open-circuit voltage of 0.75 V, a peak power density of 3.38 mW cm-2 and the yield rates of 32.7 mg h-1 cm-2 for ammonia and 889.4 mg h-1 cm-2 for formate. In a large-scale formaldehyde-nitrate battery (25 cm2 ), 99.9 % of nitrate and 99.8 % of formaldehyde are removed from simulated industrial wastewater and the electricity of 2.03 W⋅h per day is generated. Moreover, the design of such a multi-functional battery is universally applicable to the coupling of NO3 - or NO2 - reduction with various aldehyde oxidization, paving a new avenue for wastewater purification and chemical manufacturing.

Advancing wastewater treatment and metal recovery: Aminated ZIF-8 composite cellulose aerogel as an innovative biomass adsorbent for enhanced molybdenum ion adsorption

Biomass adsorbents possess significant potential for both metal recovery from industrial leaching solutions and wastewater treatment. However, standalone biomass materials suffer from the drawback of low adsorption capacity. In this study, by the combination of metal–organic frameworks (MOFs) with organic biomaterials, a novel aerogel of aminated ZIF-8 composite cellulose (CPEZN) was developed for molybdenum ions adsorption, and the incorporation of aminated ZIF-8 improved the availability of reactive groups. The unique aerogel structure effectively prevented the accumulation of MOFs, thereby increasing the specific surface area and improving the exposure of active site. In addition, the positively charged surface of CPEZN effectively adsorbed molybdenum ions. Experimental results showed that the introduction of ZIF-8-NH2 improved the adsorption performance of the composites. The adsorption of Mo(VI) followed the Langmuir adsorption isotherm model, and its adsorption rate followed the pseudo-second-order model. The adsorbent exhibited a maximum Mo(VI) adsorption capacity of 872.39 mg/g at pH = 3, and a removal rate of more than 80 % in mixed coexisting ion solutions. Moreover, the adsorbent demonstrated good stability, with a removal rate of above 80 % after 5 cycles of adsorption. Comprehensive characterizations revealed that the adsorption mechanism of Mo(VI) on CPEZN was a synergistic effect of chemisorption, electrostatic interaction, redox, and complex ligand processes. The simulated industrial wastewater adsorption experiment showed that the prepared adsorbent had good removal ability for molybdenum ions. This study not only provides a reference for the design and preparation of MOF and biomass-based composite adsorbent materials, particularly in terms of understanding the adsorption mechanism and designing high-capacity functional groups, but also provides a theoretical basis for its practical application.

Evaluation of adsorption treatment method for removal of phenol and acetone from industrial wastewater

Due to the toxins included in wastewater, wastewater reuse is becoming more and more important as a method of protecting the aquatic environment and conserving freshwater resources. Components of organic matter coming from wastewater treatment plant effluents are among the factors to be concerned about for human and environmental health. Therefore, to solve this problem, the objectives of this study were to treat simulated industrial wastewater for the removal of organic components (phenol, acetone, and mixed components) by batch adsorption system using different types of charcoal adsorbents such as; granular charcoal (GC), powder charcoal artificial (PCA), and powder charcoal commercial (PCC). To find the best operating conditions for removal efficiency, the effects of contact time, adsorbent dose, organic component concentration, pH, and shaking speed were studied. The characterization properties of the adsorbent were determined by utilizing Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The adsorption isotherm models of Langmuir and Freundlich, as well as the kinetic models of pseudo-first-order and pseudo-second-order, were investigated. The highest phenol, acetone, and mixed components removal efficiency were 93.79% (residual = 0.310 ppm), 97.08% (residual = 0.146 ppm), and 84.19% (residual = 0.790 ppm), respectively, at 1 g/L powder charcoal commercial adsorbent, 120 min of contact time, 5 ppm of organic component concentration, 150 rpm of mixing speed, and acid pH = 3 of solution. According to the results, it was found that the best type of charcoal was powder charcoal commercial for the treatment of organic components to produce quality water that meets the standards of the World Health Organization (WHO), and the best adsorption isotherm model was the Langmuir model for acetone treatment but the Freundlich model for phenol treatment.

Facile fabrication of highly efficient bifunctional polydopamine–polyethyleneimine copolymerization‐modified magnetic material and its effective applications for both adsorption of gold ions and catalytic reduction of 4‐nitrophenol

AbstractThe heavy metal ions and organic pollutants are major harmful substances in wastewater because of their toxicity on human health and environment. Nowadays, the adsorption–catalysis treatment to remove them simultaneously is still a challenge because of their different reaction mechanisms. Herein, a novel bifunctional polymer magnetic material Fe3O4@PDA‐PEI was successfully developed through a facile co‐deposition method by the copolymerization modification of polydopamine (PDA) and polyethyleneimine (PEI) on magnetic ferroferric oxide, which can both be utilized for both heavy metal ion removal from simulated industrial wastewater and further effective catalytic reduction of toxic 4‐nitrophenol (4‐NP) to useful 4‐aminophenol. The maximum adsorption capacity of Fe3O4@PDA‐PEI for gold ions was 465.12 mg/g at 35°C, and the adsorption thermodynamic parameters ΔG, ΔH, and ΔS of Fe3O4@PDA‐PEI (m(PDA):m(PEI) = 2:1) were −5.28 (35°C), 25.58, and 111.30 J K−1 mol−1, respectively. In addition, a sustainable strategy of converting gold ions to gold nanoparticles has been demonstrated for additional catalytic functionality of Fe3O4@PDA‐PEI, and Fe3O4@PDA‐PEI‐Au could effectively catalyze the reduction of 4‐NP at ambient temperature within 9 min. Fe3O4@PDA‐PEI with the advantages of facile fabrication, easy separation, excellent adsorption, and catalysis performance could be used as a promising polymer composite material in complicated wastewater environment. © 2023 Wiley Periodicals LLC.

Light-Augmented Multi-ion Interaction in MXene Membrane for Simultaneous Water Treatment and Osmotic Power Generation.

The mixing of wastewater and natural water releases abundant osmotic energy. Harvesting this energy could significantly reduce the energy and economic cost of water treatment, leading to sustainable wastewater treatment technology. Yet, such energy harvesting is highly challenging because it requires a material that is highly permeable to nontoxic ions while rejecting toxic ions in wastewater to reach high power density and prevent environmental pollution. In this work, we demonstrate that a light-augmented biomimetic multi-ion interaction in an MXene membrane can simultaneously realize high permeability of Na+ ions for enhanced osmotic power generation and high selectivity to heavy metal ions up to a ratio of 2050 for wastewater treatment. The Na+ permeability is enhanced by the photothermal effect of the MXene membrane. The transport of heavy metal ions, however, is suppressed because, under angstrom-confinement, heavy metal ions are strongly electrostatically repelled by the increased number of permeating Na+ ions. As a result, the membrane can stably generate osmotic power from simulated industrial wastewater, and the power density can be enhanced by 4 times under light illumination of approximate 1 sun intensity. This work highlights the importance of multi-ion interaction for the transport properties of ionic materials, which remains rarely investigated and poorly understood in previous studies.

Homogeneous synthesis of Schiff base modified PAMAM dendrimers/silica for efficient adsorption of Hg(II)

Water pollution caused by Hg(II) is a serious environmental issue and poses great risk to human health. Adsorption is a promising method for decontaminating aqueous Hg(II). Therefore, a family of Schiff base modified polyamidoamine (PAMAM) dendrimer/silica (G0-T1/x-S, G1-T1/x-S and G2-T1/x-S (x = 2, 4, 6)) were synthesized by homogeneous method for removing Hg(II) from water solution. The adsorption property of the adsorbents for Hg(II) was comprehensively evaluated. The adsorption capacity for Hg(II) was found to depend on the dendrimer generation. The effects of solution pH, time, temperature, and interfering metal ions on the adsorption property for Hg(II) were determined by selecting G0-T1/2-S, G1-T1/2-S and G2-T1/2-S as models. The optimal pH for the adsorption of Hg(II) is 6. Adsorption kinetic shows that the adsorption is fast at initial, and the equilibrium can be reached at 400 min. Adsorption isotherm demonstrates the increase of temperature and concentration can promote the adsorption for Hg(II). The kinetic and isotherm process can be fitted by pseudo-second-order kinetic model and Langmuir model, respectively. The adsorbents display good adsorption selectivity for Hg(II) and the functional groups of CONH, C-N, C = N and OH dominate the adsorption. The adsorbents exhibit good removal efficiency for Hg(II) from simulated industrial wastewater with the coexistence of multiple pollutants. Moreover, the adsorbents show excellent reusability as the regeneration rate of G2-T1/2-S can still maintain 92.45 % after the tenth adsorption–desorption cycles. The research work provides a feasible method for the preparation of efficient adsorbents to remove aqueous Hg(II) with practical values.

Evaluation of nitrous oxide emission during ammonia retention from simulated industrial wastewater by microaerobic activated sludge process

Considering the reciprocating processes of nitrogen gas (N2) fixation to ammonia (NH4-N) and NH4-N removal to N2 through nitrification and denitrification during wastewater treatment, a microaerobic activated sludge process (MAS) is proposed in this study as a pretreatment to retain NH4-N from high-strength nitrogenous wastewater for further NH4-N recovery through membrane technology, that is, inhibit nitrification, with sufficient removal of total organic carbon (TOC). With DO and pH control, the 3-reactor bench-scale MAS systems successfully realized an NH4-N retention rate of over 80 %, with TOC removal rates of over 90 %. In addition, the emissions of carbon dioxide (CO2) and nitrous oxide (N2O) during MAS were evaluated. The total N2O emissions were 407 and 475 mg-N/day when pH was controlled at 6.2 (S1) and 6.8 (S2), respectively, with average emission factors to total nitrogen load over 2 % in both systems. Also, the global warming potential of N2O is one order of magnitude larger than that of CO2, indicating the significance of N2O in the MAS process. Therefore, the mechanisms of N2O emission from each reactor were investigated. The first reactor, where most of the TOC was adsorbed, emitted only 1.98 % (S1) and 2.43 % (S2) of the total N2O emissions through the denitrification of nitrite and nitrate (NOx) from the return sludge. The second reactor emitted 79.9 % (S1) and 69.0 % (S2) of the total N2O with the emission rates the same order of magnitude as the NOx production rates. Multiple pathways were considered to contribute to the high N2O emissions, and biotic NH2OH oxidation was one potential pathway at pH 6.2. Finally, the third reactor emitted 9.98 % (S1) and 16.8 % (S2) of the total N2O by nitrifier denitrification. Overall, this study showed that the large N2O emissions under nitrification-inhibiting conditions of the MAS process owed to the incomplete nitrification under acidic conditions and large abundances of denitrifiers. On the other hand, the lower N2O emissions at pH 6.2 evidenced the potential N2O mitigation under slightly more acidic conditions, underlining the necessity of further study on N2O mitigation when adapting to the trend of NH4-N recovery.

Chemically cross-linked keratin and nanochitosan based sorbents for heavy metals remediation

Biosorbents for water remediation were prepared using keratin biopolymer cross-linked with nanochitosan (NC). Keratin proteins were dissolved using reducing agents and NC was incorporated with concentrations of 1, 3 and 5 % individually into the keratin solution. The mixtures were thermally treated at 75°C overnight, which promoted the formation of ester bonds between the hydroxyl groups of nanochitosan and the carboxylic groups of the keratin biopolymer. The resulting keratin derived biosorbents were characterized by X-Ray photoelectron spectroscopy, confirming the cross-linking between keratin and nanochitosan. The chicken feathers keratin (CFK) surface modifications with nanochitosan were examined with Brunauer-Emmett-Teller, scanning and transmission electron microscopies. The sorption capacity of biosorbents was tested for eight different metals simultaneously at different contact times (15, 30, 60, 120, 240, 280 mins) and pH (5.5, 7.5 and 8.5), including arsenic, selenium, chromium, nickel, cobalt, lead, cadmium and zinc, using simulated industrial wastewater water containing 600 μgl−1 concentration of each metal. The synthesized environmentally benign biosorbents exhibited biosorption of metals upto 98 % at pH 7.5 and a contact time of 24 h, showing their potential for industrial wastewater remediation.

Carbon‐based composite nanofibers for photocatalytic degradation of methylene blue dye under visible light

AbstractPhotocatalytic degradation from Photocatalytic Nanomaterials composites is a great possibility to investigate the energy shortage and potential natural risks determined by nanomaterial composites. Graphite oxide and carbon quantum dots (CQDs) were added to Polyacrylonitrile nanofibers to improve the photocatalytic activity and mechanical qualities of the composite nanofibers. Under visible light irradiation, the photocatalytic degradation of organic dyes—methylene blue dye from the simulated industrial wastewater has been studied. Electrospinning is used to create polyacrylonitrile nanofibers, which are then chemically cross‐linked with graphite oxide and CQDs to get efficient photocatalytic degradation. In‐depth analysis has been done on every parameter relating to dyes and the photocatalytic degradation mechanism. Using scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy analysis, the surface sensitization and morphological changes of the synthesized composite nanofibers were investigated. With a 100% degradation efficiency for MB after 25 min, sensitized CQDs with graphite oxide demonstrated better efficiency in the degradation of MB when compared with pristine elements. The ideal catalytic conditions, including pH and starting organic dye content, were discussed. Methylene blue dye degraded more effectively as initial concentrations dropped. The reaction rate slows down at a pH of 7. The proposed composite demonstrated high stability and reusability for MB dye, and the cost‐controlling method can be utilized in advanced applications.

Simple solid-phase colorimetry for trace Cr(VI) by combination of complexation with diphenylcarbazide and ion-pair solid-phase extraction with sedimentable dispersed particulates.

A highly sensitive and simple solid-phase colorimetry for Cr(VI) was proposed. It was based on the ion-pair solid-phase extraction of Cr-diphenylcarbazide (DPC) complex with sedimentable dispersed particulates. The concentration of Cr(VI) was measured from the color tones obtained by image analysis of the photo of sediment. Various conditions, e.g., material and amounts of adsorbent particulates, chemical properties and concentration of counter ions, and pH, were optimized for the formation and quantitative extraction of the complex. In the recommended procedure, 1mL of sample was put into a 1.5mL microtube where powder form adsorbent and reagents, i.e., XAD-7HP particles, DPC, sodium dodecyl sulfate, amido sulfuric acid, and sodium chloride had been packed. The analytical operation was completed within 5min by gently shaking the microtube and allowing it to stand until enough amounts of particulates were deposited to take a picture. Chromium (VI) up to 2.0ppm was determined, and the detection limit was 0.0034ppm. The sensitivity was enough to determine Cr(VI) at lower concentrations than the water quality of standard (0.02ppm). This method was successfully applied to the analysis of simulated industrial wastewater samples. The stoichiometry of the extracted chemical species was also investigated by applying the same equilibrium model as the ion-pair solvent extraction.

Adsorptive removal of Zn, Fe, and Pb from Zn dominant simulated industrial wastewater solution using polyvinyl alcohol grafted chitosan variant resins

In this article, the efficacy of synthesized chitosan polyvinyl alcohol derivatives has been investigated for cyclic multi-heavy metal removal. Thereby, derivative resin revealed the combined benefits of chitosan and polyvinyl alcohol for multi-heavy metal removal from Zn dominant simulated industrial wastewater. Both FTIR and XRD results affirmed a strong interaction between PVA and chitosan. Batch adsorption studies were targeted for alternate choices of adsorbent-adsorbate ratio (0.2–2 g/L), contact period (5 to 720 min), and initial concentration (194.9–584.7 mg/L for Zn, 104.8–314.4 mg/L for Fe, and 2.65–7.95 mg/L for Pb). After the first cycle, the maximum adsorption capacity of 222.21, 135.14, and 4.02, respectively for Zn, Fe, and Pb was achieved for the high molecular weight chitosan-based polyvinyl alcohol derivative (high CSPVA). The alternate equilibrium and kinetic model based studies respectively confirmed the homogeneous and chemisorptive behavior of the adsorption. The cyclic desorption and regeneration studies inferred that the high CSPVA derivative resin has been highly efficient and useful sorbent for Zn, Fe, and Pb removal. Thereby, the investigations assure confidence in the relevance of the mentioned resin for real scenarios that demand the treatment of industrial multi-heavy metal containing wastewater systems.

Feasible synthesis of bifunctional polysilsesquioxane microspheres for robust adsorption of Hg(II) and Ag(I): Behavior and mechanism.

The pollution of Hg(II) and Ag(I) to water system exerts hazardous effect to aquatic ecosystem and public security. Simple strategy for constructing adsorbents to efficient remove them is greatly desired. Thus, a series of thiol and amino groups containing bifunctional polysilsesquioxanes (ASPSS) microspheres with adjustable porous structure and functional group content were synthesized by one-step feasible sol-gel process. The adsorption behavior and mechanism of ASPSS microspheres toward Hg(II) and Ag(I) was thoroughly determined. The maximum adsorption capacity of ASPSS for Hg(II) and Ag(I) are 4.32 and 3.86mmol·g-1 under 25℃. The as-prepared ASPSS microspheres can 100% selectively capture Hg(II) with the coexisting of Mn(II), Co(II), Pb(II), Cd(II), Cu(II), Fe(III). And they can 100% adsorb Ag(I) with the presence of Cd(II), Pb(II), Co(II), Ni(II), and Zn(II). Moreover, the ASPSS microspheres exhibit good removal efficiency for Hg(II) and Ag(I) from simulated industrial wastewater with the coexistence of multiple pollutants. Adsorption mechanism suggests the adsorption for Hg(II) and Ag(I) is the synergistic coordination effect of amino and thiol groups. The excellent adsorption selectivity for Hg(II) and Ag(I) is attributed to the super binding ability of these functional group. ASPSS microspheres also exhibit good regeneration ability and could be reused for removing Hg (II) and Ag(I) from aqueous solution with practical value.

Cobalt and nitrogen co-doped monolithic carbon foam for ultrafast degradation of emerging organic pollutants via peroxymonosulfate activation

Cobalt-based catalysts are expected as one of the most promising peroxymonosulfate (PMS) activators for the removal of organic pollutants from industrial wastewater. However, the easy agglomeration, difficult separation, and secondary pollution of cobalt ions limit their practical application. In this study, a novel, highly efficient, reusable cobalt and nitrogen co-doped monolithic carbon foam (Co-N-CMF) was utilized to activate PMS for ultrafast pollutant degradation. Co-N-CMF (0.2 g/L) showed ultrafast catalytic kinetics and higher total organic carbon (TOC) removal efficiency. Bisphenol A, ciprofloxacin, 2,4-dichlorophenoxyacetic acid, and 2,4-dichlorophenol could be completely degraded after 2, 4, 5, and 5 min, and the TOC removal efficiencies were 77.4 %, 68.9 %, 72.8 %, and 79.8 %, respectively, corresponding to the above pollution. The sulfate radical (SO4•-) was the main reactive oxygen species in Co-N-CMF/PMS based on electron paramagnetic resonance. The ecological structure-activity relationship program analysis via the quantitative structure activity relationship analysis and phytotoxicity assessment revealed that the Co-N-CMF/PMS system demonstrates good ecological safety and ecological compatibility. The Co-N-CMF catalyst has good catalytic activity and facile recycling, which provides a fine method with excellent PMS activation capacity for 2,4-dichlorophenol elimination from simulated industrial wastewater. This study provides new insights into the development of monolithic catalysts for ultrafast wastewater treatment via PMS activation.

Optimal synthesis of MoS2/Cu2O nanocomposite to enhance photocatalytic performance towards indigo carmine dye degradation

In this work, the nanocomposite of MoS2 nanosheets with Cu2O spheres was synthesized with different weight ratios of MoS2 and Cu2O by precipitation method and used as a potent photocatalyst for indigo carmine (IC) dye degradation. Various analytical techniques such as XRD, FTIR, FESEM, HRTEM, EDX, UV-DRS, PL, XPS, TGA, BET surface area, CV, and EIS were used to analyze the characteristics of as-synthesized MoS2/Cu2O. The electrochemical results revealed that Cu2O provides active sites as well as charge separation in Z-scheme nanocomposite which further confirmed robust coupling between MoS2 nanosheets and Cu2O spheres. The photocatalytic results showed that an optimized heterostructure consisting of Cu2O decorated on MoS2 with a weight ratio of 1:0.75 exhibited a 45 % enhancement of IC photodegradation efficiency in visible light as compared to pristine MoS2. The photocatalytic studies were also performed over simulated industrial wastewater, which is a significant aspect toward encouraging the practical application of the photocatalysis approach. The results depict that MoS2 nanosheets decorated with Cu2O spheres are valuable nanocomposites to remove organic contaminants from wastewater.

Three-dimensional porous nitrogen-doped carbon aerogels derived from cellulose@mof for efficient removal of dye in water

Three-dimensional porous nitrogen-doped carbon aerogels are synthesized by one-step carbonization of bacterial cellulose@zeolitic imidazolate framework-8 (ZIF-8) composite aerogels. The uniformly distributed Zn nanoparticles in the carbon aerogels gradually volatilize during the calcination process, and a large number of mesopores are formed in situ. After carbonization at 1000 °C, nitrogen-doped carbon aerogels (C-BZ-1000) show excellent hydrophilicity and the three-dimensional macroporous structure of composite aerogels is well preserved. The obtained C-BZ-1000 aerogels with hierarchical porous structure have large specific surface area and low density of 0.005 g cm−3, thereby realizing fast diffusion of methylene blue (MB) molecular. They have excellent adsorption performance, and the equilibrium adsorption of MB in simulated industrial wastewater can reach 227 mg g−1, which was 1.4 times higher than that of nanoporous carbon obtained by carbonization of ZIF-8 and 4.7 times higher than carbon aerogels obtained by carbonization of BC, respectively. Importantly, this current approach can be extended to more metal-organic framework and biomass materials for the design and fabrication of various advanced multifunctional materials.

Simultaneous removal of cationic dyes from simulated industrial wastewater using sulfated alginate microparticles

Double crosslinked sulfated alginate (DCSA) microparticles were applied as adsorbent for simultaneous removal of methylene blue (MB) and rhodamine B (RhB) dyes by the batch method. The adsorption process was optimized in terms of initial dyes concentrations, adsorbent amount, pH, and contact time. Equilibrium adsorption isotherm of dyes were assessed by Langmuir and Freundlich models. The results best fitted with the Langmuir adsorption isotherm model, which confirm the linearity of the process. Maximum adsorption capacities (Qm) of DCSA microparticles in single system were obtained as 612.3 and 545.2 mgg−1 for MB and RhB dyes, respectively. In contrast, Qm vales for the MB and RhB dyes in binary mixed system improved slightly up to 641.7 and 561.4 mgg−1, respectively. The adsorption kinetics for both MB and RhB dyes were well-described by pseudo-second-order model that confirm the rate-limiting step might be the chemical adsorption. The dyes-loaded DCSA microparticles were regenerated by desorption process with numerous solvents and were reused five times without a significant decrease in their adsorption performance in first three cycles (especially for MB dye). The adsorption process was computationally simulated via Grimme dispersion correction (D3) as well as radial distribution function (RDF) techniques, and the results exhibited acceptable accordance with experimental data.

High-efficiency Hg(II) adsorbent: FeS loaded on a carbon black from pyrolysis of waste tires and sequential reutilization as a photocatalyst.

Iron-sulfur nano compounds have been proven to be effective in mercury removal, but the agglomeration, poor dispersion and mobility, and easy oxidation challenges limit their application. Herein, carbon black originating from pyrolysis of waste tires was used as a carrier of nano-FeS to obtain an efficient adsorbent (C@PDA-FeS). It is found that the C@PDA-FeS shows outstanding adsorption ability, excellent selectivity, and high removal rate. A maximum adsorption capacity of 1754mg/g is obtained, and the residual Hg(II) ion concentration is as low as 3.2μg/L in the simulated industrial wastewater, which meets the industrial discharge standard under the optimal conditions. Meanwhile, the removal rate of Hg(II) ion can reach 99.8% after up to 10 cycles. More importantly, the C@PDA-FeS still shows good adsorption efficiency, and the removal rate of Hg(II) ion is over 99% (25mg/L Hg(II) concentration) after 90days of storage, demonstrating the long-term stability and promising future of the adsorbent. In addition, the waste adsorbent (C@PDA-FeS/HgS) is reused as a photocatalyst to degrade methylene blue, and the corresponding degradation rate is 92.9% (10mg/L).