Synergistic Effect Of Adsorption Research Articles

Synergistic adsorption effect on Co3O4(1 1 0) surface to promote the ethanol sensing properties: Experiment and theory

A deep understanding of the relationship between the properties and structure of transition metal oxide semiconductor gas sensors is essential for optimizing sensor design. Comparing and analyzing the sensing properties of nanomaterials with different morphologies and crystal facets by combining the experiment analysis and the density functional theory (DFT) calculations could identify and understand the corresponding mechanisms at the atomic or ionic level. Here, grown Co3O4 nanosheet (Co3O4-NS) with exposed (111) facets, and Co3O4 nanorods (Co3O4-NR) with exposed (110) facets on alumina ceramic tubes were prepared and studied in sensing ethanol. The adsorption characteristics of ethanol on the sensor surface were analyzed by DFT calculation. The results demonstrated that the sensing performance of Co3O4-NR was superior to Co3O4-NS. The adsorption of hydroxyl groups in ethanol was better than the methyl groups on the surface. The oxygen and hydrogen atoms from the hydroxyl groups in ethanol had the lowest adsorption energies (Eads = −3.44 eV) when they interact with the Co atom and the indirectly adjacent low-coordinate oxygen atoms on the (110) surface, respectively. The synergistic adsorption of target gases by exposed surface atoms induced superior sensing properties of the material.

Pseudomonas stutzeri Immobilized Sawdust Biochar for Nickel Ion Removal

Nickel ions generated from the electroplating industry and stainless steel and battery manufacturing industries contribute to water pollution, harm human health, and pose environmental risks. A long-term, sustainable, and efficient treatment method should be developed to address this issue. Bioremediation in the presence of biochar and microorganisms is a potential approach for metal ion abatement. This study evaluates the feasibility of Pseudomonas stutzeri immobilized sawdust biochar (PSDB) for Ni2+ removal. Sawdust biochar was prepared by pyrolyzing in a muffle furnace and was characterized using SEM, FTIR, and BET. The influence of biochar preparation parameters such as pyrolysis temperature, time on biochar yield, and impact on cell immobilization was investigated. The effect of various parameters, such as incubation time, pH, temperature, and biocatalyst dosage, was studied. The total Ni2+ in solution was analyzed using inductively coupled plasma optical emission spectrometry. PSDB showed an 83% Ni2+ removal efficiency and reusability up to three cycles. FT-IR analysis revealed that the mechanism of Ni2+ removal by PSDB was the synergistic effect of adsorption by biochar and bioaccumulation by P. stutzeri. This study presents a novel approach for environmental application by utilizing waste biomass-derived biochar as a carrier support for bacteria and an adsorbent for pollutants.

Adsorption and catalytic removal of methyl orange from water by PIL-GO/TiO2/Fe3O4 composites

In this paper, an organic-inorganic hybrid material was synthesized via a simple but effective method, the novel material PGO-TiO2/Fe3O4 (PGTF) was produced by loading TiO2 and Fe3O4 onto polymeric ionic liquid(PIL) functionalized graphene oxide(GO). The successful synthesis of PGTF and related structural feature were confirmed by a series of characterizations. The results of UV diffuse reflectance (DRS) demonstrated that the incorporation of PGO-Fe3O4 to TiO2 shifted the light absorption of TiO2 from ultraviolet (UV) to visible region. The band gap energy of the PGTF reduced to1.92 eV as compared to TiO2 (3.12 eV). Different materials were used to remove methyl orange (MO) from the aqueous solution. The results showed that PGTF had a superior capacity to remove dye due to the synergistic effects of adsorption and photocatalysis. The excellent adsorption properties may result from the high specific surface area of GO and the –NH2 in the PIL. The polyionic liquid absorbed electrons due to the electrostatic action of the cation head in the polyionic liquid and GO which had high conductivity favored electron transport. The photocatalytic effectiveness increased as a result of the separation of photoexcited electron-hole pairs. The Langmuir model was investigated to evaluate the adsorption equilibrium behavior of MO dyes by PGTF. The maximum adsorption capacity(Qmax) was 67.88 mg/g for MO dyes. The pseudo-second-order kinetic model, with a correlation coefficient of 0.999, provided a good fit for the adsorption kinetic processes. The adsorption rate constant K2 obtained by this model is 0.0072 g/(mg*min). The degradation rate constant of PGTF for MO in the photocatalytic stage was 0.00881 min−1, which exhibited 3.7, 7.5 and 3 times higher than that of TiO2, FT and GTF. The main reactive species in the degradation process were O2−、·OH、h+. PGTF had excellent repeatability because of the presence of Fe3O4. They can be easily separated from the water. These results indicated that the PGTF composites hold great potential for removing MO from wastewater.

Ceftriaxone sodium degradation by carbon quantum dots (CQDs)-decorated C-doped α-Bi2O3 nanorods

A novel carbon quantum dots decorated C-doped α-Bi2O3 photocatalyst (CBO/CQDs) was synthesized by solvothermal method. The synergistic effect of adsorption and photocatalysis highly improved contaminants removal efficiencies. The ceftriaxone sodium degradation rate constant (k) of CBO/CQDs was 11.4 and 3.2 times that of pure α-Bi2O3 and C-doped α-Bi2O3, respectively. The interstitial carbon doping generated localized states above the valence band, which enhanced the utilization of visible light and facilitated the separation of photogenerated electrons and holes; the loading of CQDs improved the charge carrier separation and extended the visible light response; the reduced particle size of CBO/CQDs accelerated the migration of photogenerated carriers. The •O2− and h+ were identified as the dominant reactive species in ceftriaxone sodium degradation, and the key role of •O2− was further investigated by NBT transformation experiments. The Fukui index was applied to ascertain the molecular bonds of ceftriaxone sodium susceptible to radical attack, and intermediates analysis was conducted to explore the possible degradation pathways. The toxicity evaluation revealed that some degradation intermediates possessed high toxicity, thus the contaminants require sufficient mineralization to ensure safe discharge. The present study makes new insights into synchronous carbon dopping and CQDs decoration on modification of α-Bi2O3, which provides references for future studies.

Removal of methylene blue using a novel generation photocatalyst based on nano-SnO2/wild plumb kernel shell biochar composite

A series of measurement results revealed that the nano-SnO2 (n-SnO2) nanoparticles were spread uniformly on the carbon surface inside the wild plum (Prunus domestica) kernel shell biochar (WPKSB) structure. The addition of hydrothermally synthesized n-SnO2 to WPKS improved both the adsorption capacity and the photocatalytic potential of WPKSB for methylene blue (MB) removal. When the initial MB content was 5 mg/L, the n-SnO2@WPKSB composite demonstrated high MB removal efficiency under UV light via a combined effect of adsorption and photocatalysis. The n-SnO2@WPKSB composite removed 99.5 (±0.4) % of the MB from the dye-polluted water sample in 105 minutes at pH of 7.0. Because of the synergistic effect of adsorption and photodegradation, the composite was more effective at treating the aqueous MB solution than WPKSB and n-SnO2 alone. Reusability tests were run to remove MB to assess the composite structure’s chemical stability and catalytic capacity. The n-SnO2@WPKSB composite was characterized using X-ray Diffraction, Fourier Transform infrared and Scanning Electron Microscopy. This research investigates how to make metal oxide/biochar nanocomposites with exceptional adsorption and photocatalysis properties for the oxidation and removal of MB.

Construction of dual Z-scheme UNiMOF/BiVO4/S-C3N4 photocatalyst for visible-light photocatalytic tetracycline degradation and Cr(VI) reduction

Rapid recombination of the photogenerated carrier, a limited range of photoexcitation, and unsatisfactory photocatalytic activity are the limiting factors in photocatalytic applications. Accelerating photogenerated carrier transfer and constructing surface active sites have become critical tasks. In this study, a dual Z-scheme UNiMOF/BiVO4/S-C3N4 (NBSCN) photocatalyst with a 2D/3D/2D structure was successfully constructed. Under visible-light irradiation, NBSCN outperforms single and binary composites in photocatalytic tetracycline photodegradation and Cr(VI) photoreduction due to the synergistic effect of adsorption and photocatalysis. The maximum photocatalytic efficiency of tetracycline (90.1 %) and Cr(VI) (93.6 %) in 120 min was achieved by NBSCN-20 %. The exceptional photocatalytic activity of NBSCN-20 % can be attributed to the large specific surface area, increased active sites, improved visible-light absorption ranges, and the construction of heterojunctions. The fabricated dual Z-scheme heterojunction at the interface of NBSCN reduces the recombination rate of photogenerated carriers and widens the range of light absorption. NBSCN-20 % exhibits excellent stability in the process of cyclic experiments. On the basis of the results, the feasibility of the dual Z-scheme mechanism is proposed. This work demonstrates that NBSCN-20 % photocatalyst has promising application prospects in removing heavy-metal ions and organic pollutants from aqueous environments.

Efficient degradation of VOCs using semi-coke activated carbon loaded 2D Z-scheme g-C3N4-Bi2WO6 photocatalysts composites under visible light irradiation

The coal chemical industry generates large quantities of volatile organic compounds (VOCs) and solid wastes. Within this work, porous semi-coke activated carbon (SAC) was produced from solid waste semi-coke (SC) powder. Through loading high performance photocatalysts onto SAC to efficiently degrade VOCs using synergistic effects of adsorption and photocatalysis, acheiving the resourcefulness of solid waste. The specific surface area of the prepared SAC can reach 619.27 m2.g−1, which was effective against the adsorption of VOCs. An one-step hydrothermal method was used to load a 2D Z-scheme g-C3N4-Bi2WO6 (NB) photocatalyst on a semi-coke activated carbon. The 50 wt% NB/SAC material degraded formaldehyde, benzene and toluene up to 93.6%, 84.4% and 78.8% in 130 min under visible light irradiation, being 6.09, 4.55 and 4.75 times higher than that of a single photocatalyst, respectively. The capture experiments showed that hydroxyl radicals (⋅OH) and superoxide radicals (⋅O2–) were the active species in the degradation pathway. The material maintained a high degradation performance of 84.8%, 79.6% and 74.0% even after five cycles. In this study, the mechanism of using SAC as a substrate to enhance performance in photocatalytic degradation was described. The results of this study offered new insights into the resourcefulness of solid waste and the effective degradation of VOCs. It also offered a promising theoretical foundation for the exploitation and utilization of high-performance photocatalysts.

Activation of bisulfite by LaFeO3 loaded on red mud for degradation of organic dye.

In this study, red mud (RM) was used as a support for LaFeO3 to prepare LaFeO3-RM via the ultrasonic-assisted sol-gel method for the removal of methylene blue (MB) assisted with bisulfite (BS) in the aqueous solution. Characterization by scanning electron microscopy and the Brunauer-Emmett-Teller method indicated that LaFeO3-RM exhibited a large surface area and porous structure with a higher pore volume (i.e. 10 times) compared with the bulk LaFeO3. The XRD, XPS and FTIR results revealed that the support of porous RM not only dispersed LaFeO3 particles but also increased Fe oxidation capability, oxygen-containing functional groups and chemically adsorbed oxygen (from 44.3% to 90.3%) of LaFeO3-RM, which improved the catalytic performance in structure and chemical composition. MB was removed through the synergistic effect of adsorption and catalysis, with MB molecules first absorbed on the surface and then degraded. The removal efficiency was 88.19% in the LaFeO3-RM/BS system under neutral conditions but only 27.09% in the LaFeO3/BS system. The pseudo-first-order kinetic constant of LaFeO3-RM was six times higher than that of LaFeO3. Fe(III) in LaFeO3-RM played a key role in the activation of BS to produce by the redox cycle of Fe(III)/Fe(II). Dissolved oxygen was an essential factor for the generation of . This work provides both a new approach for using porous industrial waste to improve the catalytic performance of LaFeO3 and guidance for resource utilization of RM in wastewater treatment.

Enhanced Performance of Li-S Batteries due to Synergistic Adsorption and Catalysis Activity within a Separation Coating Made of Hybridized BNNSs/N-Doping Porous Carbon Fibers.

Lithium-sulfur (Li-S) batteries with high theoretical energy density are considered as the most promising devices for rechargeable energy-storage systems. However, their actual applications are rather limited by the shuttle effect of lithium polysulfides (LiPSs) and the sluggish redox kinetics. Here, the boron nitride nanosheets are homodispersedly embedded into N-doping porous carbon fibers (BNNSs/CHFs) by an electrospinning technique and a subsequent in situ pyrolysis process. The hybridized BNNSs/CHFs can be smartly designed as a multifunctional separation coating onto the commercial PP membrane to enhance the electrochemical performance of Li-S batteries. As a result, the Li-S batteries with extra BNNSs/CHF modification deliver a highly reversible discharge capacity of 830.4 mA h g-1 at a current density of 1 C. Even under 4 C, the discharge specific capacity can reach up to 609.9 mA h g-1 and maintain at 553.9 mA h g-1 after 500 cycles, showing a low capacity decay of 0.01836% per cycle. It is considered that the excellent performance is attributed to the synergistic effect of adsorption and catalysis of the BNNSs/CHF coating used. First, this coating can efficiently reduce the charge transfer resistance and enhance Li-ion diffusion, due to increased catalytic activity from strong electronic interactions between BNNSs and N-doping CHFs. Second, the combination of polar BNNSs and abundant pore structures within the hybridized BNNSs/CHF networks can highly facilitate an adsorption for LiPSs. Here, we believed that this work would provide a promising strategy to increase the Li-S batteries' performance by introducing hybridized BNNSs/N-doping carbon networks, which could efficiently suppress the LiPSs' shuttle effect and improve the electrochemical kinetics of Li-S batteries.

“1+1>2”: Highly efficient removal of organic pollutants by composite nanofibrous membrane based on the synergistic effect of adsorption and photocatalysis

• A dual-functional nanofibrous membrane material was prepared for wastewater remediation. • The adsorption facilitated and accelerated the photocatalytic degradation reaction. • The photocatalysis regenerated the adsorption active site and realized green recycle. • The synergistic effect of adsorption and photocatalysis was investigated systematically. • The synergy produced a “1+1>2” effect for highly efficient removal of pollutants. Adsorption and photocatalysis are regarded as two desirable technologies for wastewater remediation, but are still unsatisfactory in removal effect, eco-friendly regeneration and facile reusability. In this study, we developed a composite nanofibrous membrane material with excellent removal performance for organic pollutants based on synergistic adsorption and photocatalysis. A novel boron-doped, nitrogen-deficient graphitic carbon nitride (B-C 3 N 4 ) photocatalyst as well as an amphiphilic copolymer of methyl methacrylate and acrylic acid (p(MMA-AA)) were synthesized respectively, and then used to modify polyethersulfone for the fabrication of composite nanofibrous membrane with improved hydrophilicity, negatively-charge property and enhanced visible light response simultaneously. Subsequently, the synergistic effect of adsorption and photocatalytic degradation for organic pollutants were identified especially and resulted in an excellent removal efficiency even superior to the combination of adsorption and photocatalytic degradation, which could be called a “1+1>2” effect. In addition, the regeneration and reusability, the purification ability for multicomponent wastewater, and the photocatalytic mechanism, were investigated and discussed systematically. In this work, we not only prepared the nanofibrous membrane with synergistic effect of adsorption and photocatalysis, but also provided a versatile approach to design dual-functional support material to ensure the practical applications of powdery photocatalyst in wastewater treatment.

Synergistic effect of adsorption and photocatalysis of BiOBr/lignin-biochar composites with oxygen vacancies under visible light irradiation

Effective utilization solar energy through photocatalysis is an ideal way to solve environmental problems and achieve sustainable development. Herein, a novel BiOBr/Lignin-Biochar photocatalyst has been successfully synthesized by a simple hydrothermal method. The number of oxygen vacancies of BiOBr increased after C doping, which improves visible-light absorbance, reduces the recombination of photo-generated carriers and promotes O2 activation to produce O2−. UV–vis DRS result demonstrated that the visible-light absorption capacity of BiOBr improved significantly with the addition of lignin. Compared with BiOBr, the adsorption and photocatalytic ability of BiOBr/Lignin-Biochar composites were greatly enhanced due to enriched oxygen vacancies and the congenerous effect between BiOBr and lignin-biochar. The RhB removal with pure BiOBr and BiOBr/Lignin-Biochar under visible-light irradiation at 60 min was 54.5% and 99.2%, respectively, owing to the interface interaction between BiOBr and lignin-biochar promoted the separation between electron and holes and the enrichment of RhB around the photocatalysts. Notably, the bandgap of BiOBr/Lignin-Biochar composites decreased from 2.65 eV to 2.56 eV after C doping, useful for visible-light-driven photocatalysis. The superoxide radical anions (O2−) were the main active species, as demonstrated by free radical capture experiments and ESR characterization results. Hence, the present work provides new insights into constructing cost-effective, high-efficiency composite materials for environmental remediation.

Efficient chromium (VI) removal from wastewater by adsorption-assisted photocatalysis using MXene

Hexavalent chromium, Cr(VI), is considered hazardous heavy metal in water bodies that can cause severe effects on human health and the environment. Over the years, myriad attention has been focused on developing photocatalysts to remove Cr(VI) from wastewater. However, broad bandgap energy and the high electron recombination rate of these conventional photocatalysts have limited their photocatalytic ability. Therefore, efficient photocatalytic materials for Cr(VI) removal in wastewater is strongly demanded. In this study, delaminated MXene was successfully synthesised and used to remove Cr(IV) from the aqueous solution. The synthesised delaminated MXene was characterised using XRD, EDX, FTIR, FESEM, nitrogen adsorption-desorption analysis, TGA, UV-Vis-NIR spectroscopy and XPS. Based on the results, the optimum operating conditions for Cr(VI) removal by the synthesised MXene was obtained at pH 4 with photocatalyst loading of 1.5 g/L and Cr(VI) initial concentration of 5 mg/L. The removal efficiency of Cr(VI) via adsorption-assisted photocatalysis over various concentrations was around 3.1–28.9% higher than adsorption, verifying a synergistic effect of adsorption and photocatalysis by the delaminated MXene. The isotherm of Cr(VI) adsorption was fitted by the Langmuir model (R2 > 0.9848) and was found better than the Freundlich model (R2 > 0.8824). Meanwhile, the time dependence of Cr(VI) adsorption was well fitted to the pseudo-second-order kinetic model with R2 > 0.9999. In conclusion, the results obtained suggest that the delaminated MXene possesses excellent properties and the ability to remove Cr(VI) via adsorption-assisted photocatalysis and has great potential to be used for industrial wastewater applications.

In Situ Synthetic ZIF-8/Carbon Aerogel Composites as Solid-Phase Microextraction Coating for the Detection of Phthalic Acid Esters in Water Samples.

In this study, a hybrid composite featuring zeolitic imidazolate framework-8/carbon aerogel (ZIF-8/CA) was synthesized via in situ nucleation and growth of ZIF-8 nanoparticles inside carbon aerogels. The novel material was used as the solid-phase microextraction (SPME) coating for the five phthalic acid esters (PAEs) detection by coupling with a gas chromatography–flame ionization detector (GC-FID). Compared with bare carbon aerogel, the ZIF-8/CA presented the best performance, which is attributed to the unique advantages between the high surface area of CA and high hydrophobic properties, the thermal stability of ZIF-8, and their synergistic adsorption effects, such as molecular penetration, hydrogen bond, and π–π stacking interactions. Under the optimized conditions, the as-proposed ZIF-8/CA fiber provided a wide linearity range from 0.2 to 1000 μg L−1 and a low detection limit of 0.17–0.48 μg L−1 for PAEs analysis. The intra-day and inter-day of signal fiber and the fiber–fiber relative standard deviations were observed in the ranges of 3.50–8.16%, 5.02–10.57%, and 5.66–12.11%, respectively. The method was applied to the determination of five PAEs in plastic bottled and river water samples.

High-efficiency removal of antibiotic pollutants by magnetic carbon aerogel: Inherent roles of adsorption synergistic catalysis

For the persulfate-based advanced oxidation processes (AOPs), the difficulty of separating powdered carbon catalyst, the leaching of pure metal catalyst and high consumption of catalyst limit the large-scale application of this technique. To overcome the above-mentioned drawbacks, the magnetic carbon aerogels (SA-Fe, SA-Co and SA-Ni) with high specific surface area were synthesized by using sodium alginate as carbon precursor, KOH as pore-forming agent, and various metal salts as magnetic dopants. The specific surface area of SA-Fe, SA-Co and SA-Ni reached up to 2760, 2988, and 2420 m2/g, which showed excellent removal performance for high concentration tetracycline hydrochloride (TC) wastewater. Among them, SA-Fe with Fe0 nanoparticles and graphitized structure displayed the optimal removal capacity of 2000 mg/g for TC, which was attributed to the synergistic effect of adsorption, radical pathway and non-radical pathway. The removal efficiencies of TC and total organic carbon (TOC) at high concentration of 200 ppm were 100% and 71.66% by only using 0.1 g/L of SA-Fe. SA-Fe also displayed excellent reusability, and the TC removal efficiency after 5 cycles only lost 4%. More interestingly, the adsorption and singlet oxygen (1O2) played more important roles than other mechanisms. The combing of carbon materials and metal dopants not only provided a magnetic property but also changed the degradation pathway. This study provided a high-performance, eco-friendly and cost-effective catalyst for the removal of antibiotic pollutants by persulfate-based AOPs.

Enhanced photodegradation of tylosin in the presence of natural montmorillonite: Synergistic effects of adsorption and surface hydroxyl radicals

Tylosin (TYL) is a ubiquitous macrolide antibiotic which has been frequently detected in natural aqueous environment. Montmorillonite (MMT), a major component of natural suspended particles, plays essential roles in the transportation and transformation processes of various organic contaminants. This study systematically investigated the photodegradation behavior and mechanism of TYL in MMT suspensions under simulated sunlight irradiation. In the existence of 0.1 g L−1 Na-MMT, >80.8 % TYL was degraded after 8 h irradiation, which was significantly higher than that in the absence of MMT (42.5 %). Further mechanistic studies suggested that the synergistic effects including the formation of surface complex and the generation of surface hydroxyl radicals play essential roles in the accelerated TYL phototransformation. Meanwhile, other factors like exchangeable cations of MMTs, pH and ionic strength could also strongly influence the TYL photodegradation. The probable degradation pathways of TYL in MMT suspension was further proposed based on the detected intermediates and DFT calculations. Photobacterium phospherium T3 bioluminescent assay revealed that the photodegradation products of TYL have a lower acute toxicity than bulk TYL, especially in the presence of MMT. This study provides new insights for the photodegradation pathways of organic contaminants in aqueous environments, which is of great importance for assessing the fate and risk of emerging pollutants in natural surface water bodies.

Study of the synthesis, adsorption property, and photocatalytic activity of TiO2/coal gasification fine slag mesoporous silica glass microsphere composite.

In this study, TiO2/MSGM composite material with adsorption-photocatalytic properties was prepared by extracting mesoporous silica glass microsphere (MSGM) from coal gasification fine slag (CGFS) as a novel TiO2 carrier. The results of characterization and properties of the composite showed that MSGM could improve the adsorption capacity and photocatalytic activity of the composite by improving the pore structure of the composite, hindering the growth of TiO2 particles, increasing the phase transition temperature of TiO2, enhancing the dispersion of TiO2 particles. The sample 1:3-TiO2/MSGM-2-500 prepared under the optimized conditions possesses satisfactory morphology characteristics, high adsorption capacity, and photocatalytic activity to rhodamine B (RhB). The synergistic effects of adsorption and photocatalytic significantly increase the total removal rate of RhB. This study not only provides a new direction for high-value-added resource utilization of CGFS but also gives a new kind of low-cost carrier material with adsorption property for TiO2 loading to remove organic dye pollutants.

Effective Removal of Methylene Blue on EuVO4/g-C3N4 Mesoporous Nanosheets via Coupling Adsorption and Photocatalysis.

In this study, we first manufactured ultrathin g-C3N4 (CN) nanosheets by thermal etching and ultrasonic techniques. Then, EuVO4 (EV) nanoparticles were loaded onto CN nanosheets to form EuVO4/g-C3N4 heterojunctions (EVCs). The ultrathin and porous structure of the EVCs increased the specific surface area and reaction active sites. The formation of the heterostructure extended visible light absorption and accelerated the separation of charge carriers. These two factors were advantageous to promote the synergistic effect of adsorption and photocatalysis, and ultimately enhanced the adsorption capability and photocatalytic removal efficiency of methylene blue (MB). EVC-2 (2 wt% of EV) exhibited the highest adsorption and photocatalytic performance. Almost 100% of MB was eliminated via the adsorption–photocatalysis synergistic process over EVC-2. The MB adsorption capability of EVC-2 was 6.2 times that of CN, and the zero-orderreaction rate constant was 5 times that of CN. The MB adsorption on EVC-2 followed the pseudo second-order kinetics model and the adsorption isotherm data complied with the Langmuir isotherm model. The photocatalytic degradation data of MB on EVC-2 obeyed the zero-order kinetics equation in 0–10 min and abided by the first-order kinetics equation for10–30 min. This study provided a promising EVC heterojunctions with superior synergetic effect of adsorption and photocatalysis for the potential application in wastewater treatment.

The characterization of a novel magnetic biochar derived from sulfate-reducing sludge and its application for aqueous Cr(Ⅵ) removal through synergistic effects of adsorption and chemical reduction

Removal of heavy metals from the aqueous environment via physiochemical adsorption always remains a great challenge owing to the slow kinetics and low removal capacity for the conventional adsorbent. In this study, the sulfate-reducing bacteria (SRB)-rich anaerobic sludge was pyrolyzed for the preparation of magnetic biochar, i.e. SBC-20-500 (SBC: sulfate-reducing sludge-based biochar; 20 denotes the biochar dosage, namely 8 g dried sludge in 400 mL iron solution which is equal to 20 g/L; 500 represents the pyrolysis temperature, i.e. at 500 °C) with tunable pore structure and surface properties towards efficient removal of chromium (Cr (Ⅵ)). The characterization revealed that magnetic biochar SBC-20-500 exhibited higher surface area and larger pore volume compared to non-magnetic SBC-500. Batch experiments on Cr (Ⅵ) removal were performed under different biochar dosages, pH values, initial Cr (Ⅵ) concentrations and temperatures. The results illustrated that magnetic biochar demonstrated much larger Cr (Ⅵ) adsorption capacity with qe of 5.3585 mg/g as compared to non-modified one (qe = 0.7206 mg/g). The maximum Cr (Ⅵ) removal efficiency of SBC-20-500 reached approximately 93.7% within 24 h under the conditions of pH = 3.0, biochar dosage = 0.8 g and initial Cr (Ⅵ) concentration = 50 mg/L. The kinetic and isotherm fitting results suggested that the pseudo-second-order kinetic and Langmuir isotherm model were more suitable for describing the adsorption behavior of Cr (Ⅵ) by SBC-20-500. The XPS and FTIR results confirmed that chemical reduction of Cr (Ⅵ) to Cr (Ⅲ) also played a role in Cr (Ⅵ) removal in the presence of SBC-20-500. Moreover, the Cr (Ⅵ) removal capacity could still achieve 3.50 mg/g even after five adsorption-desorption cycles, indicating the satisfactory reusability of the as-prepared biochar. The results of this study may provide a win-win approach for simultaneous resource recovery from the wasted sulfate-reducing sludge (SRS) and highly-efficient remediation of Cr (Ⅵ)-contaminated environment.

Bismuth (III)-based metal-organic framework for tetracycline removal via adsorption and visible light catalysis processes

At present, studies on metal-organic frameworks (MOFs) have mainly focused on transition metals and lanthanides. In this study, the main group element bismuth (Bi) with low toxicity, low cost, light response, and good chemical stability was used as the metal center, and terephthalic acid was used as the ligand to prepare bismuth terephthalate material (BiBDC) through a hydrothermal method for the adsorption and photocatalytic degradation of tetracycline (TC). Under visible light irradiation, approximately 92.4% of TC (10 mg/L) was removed within 40 min through the synergistic effect of adsorption and photocatalytic degradation process. The entire process of TC removal could achieve sustainable environmental remediation without the need for additional oxidants. Meanwhile, after 5 cycles BiBDC still reached over 74% TC removal. The zeta potential, BET, FT-IR, and XPS analysis results confirmed the interaction between TC and BiBDC, in which the TC adsorption mechanism on BiBDC mainly involved pore-filling, electrostatic interactions, complexation, and H-bonds. The results of free radical trapping and EPR experiments showed that h+ played the dominant role in the photocatalytic degradation of TC, and·O2- also contributed to this process. In addition, BiBDC showed better TC removal performance in natural water bodies. This study provides some implications for the construction of BiBDC as a novel and promising dual-functional material for the elimination of pollutants in water treatment.

Fabricating S-scheme BiOBr/Zn2In2S5 heterojunction for synergistic adsorption-photocatalytic degradation of tetracycline

Harnessing affordable photocatalysts with high performance for boosting charge separation is an effective strategy to reinforce wastewater contaminant control. Herein, we reported a self-assembled S-scheme heterostructure BiOBr/Zn2In2S5 (BZS) nanoflower with the formation of internal electric field to promote the synergistic effect of adsorption and photocatalysis. The result showed that 7 wt% BiOBr/Zn2In2S5 (BZS-7) has highest tetracycline (TC) adsorption capacity of 34.85 mg g−1, which was fitted well the pseudo-second-order and Langmuir isotherm models. Then the synergistic degradation rate could reach 97.52% after 40 min visible light irradiation, which was 1.34 times higher than that of Zn2In2S5. BZS-7 also performed excellent adsorption-photocatalytic synergy on the removal of TC in simulated seawater and continuous flow reactor, with removal efficiency about 81.11% and 34.35%, respectively. The improved performance could be attributed to unique structures and high exposure surface of reassembled morphologies after the introduction of BiOBr. The antibacterial activity and ecotoxicity evaluation of TC intermediate byproducts indicated that the proposed degradation pathways presented reduced acute and chronic toxicity. The synergistic process of cost-effective S-scheme heterojunction photocatalysts holds the research for practical on-site wastewater remediation.