Enhanced Removal Efficiency Research Articles

Fast Capture and Efficient Removal of Bloom Algae Based on Improved Dielectrophoresis Process

A dielectrophoresis (DEP) method for direct capture and fast removal of Anabaena was established in this work. The factors affecting the removal efficiency of Anabaena were investigated systematically, leading to optimized experimental conditions and improved DEP process equipment. The experimental results showed that our improved DEP method could directly capture Anabaena in eutrophic water with much enhanced removal efficiency of Anabaena from high-concentration algal bloom-eutrophication-simulated solution. The removal rate could increase by more than 20% after applying DEP at 15 V compared with a pure filtration process. Moreover, the removal rate could increase from 38.76% to 80.18% in optimized experimental conditions (the initial concentration of 615 μg/L, a flow rate of 0.168 L/h, an AC voltage of 15 V, and frequency of 100 kHz). Optical microscopic images showed that the structure of the captured algae cells was intact, indicating that the DEP method could avoid the secondary pollution caused by the addition of reagents and the release of phycotoxins, providing a new practical method for emergent treatment of water bloom outbreaks.

Photocatalytic degradation of TiO2 via incorporating Ti3C2 MXene for methylene blue removal from water

The photocatalytic degradation of TiO2 as the best method to solve the pollution of dye wastewater has been widely studied. However, the photocatalytic degradation efficiency of TiO2 needs to be further improved even though much effort has been paid, especially under visible (Vis) light. TiO2/MXene composites were synthesized by low temperature hydrothermal reaction using TiO2 (P25) and MXene nanosheets as raw materials for the degradation of methylene blue (MB) dye. The removal rate of MB was effectively improved by the combination of TiO2 with MXene materials. The best removal efficiency was achieved at a mass ratio (4:1) of TiO2 to MXene. The removal rate of TiO2/MXene composite materials for MB under ultraviolet light was 96.44%, which was 29.83% higher than that of pure TiO2. Under Vis light, the removal rate of MB was 8.26 times higher (40.19%) than that of pure TiO2. In addition, the degradation process of MB dye was significantly promoted under both external and visible light. Therefore, the utilization efficiency of Vis light was greatly improved, and the degradation process of MB dye was promoted. The enhancement of removal efficiency was attributed to the enhanced charge anti-recombination and high adsorption capability toward MB. This work successfully improved the rate of dye removal of TiO2 by incorporating MXene nanosheets, heralding the exciting prospects of TiO2/MXene composites in dye wastewater treatment.

Dual-propelled PDA@MnO2 nanomotors with NIR light and H2O2 for effective removal of heavy metal and organic dye

Self-propelled micro/nanomotors hold significant potential to achieve innovative pollutant removal application. Most current micro/nanomotors are designed for single modal propulsion and a specific type of contaminant, resulting in limited applications in complicated water environments. Herein, we develop a dual-propelled asymmetric bowl-like structured polydopamine (PDA)@MnO2 nanomotor, which possesses the capacity of both near-infrared (NIR) light and hydrogen peroxide (H2O2) propulsion. The PDA@MnO2 nanomotors were synthesized by introducing many thin MnO2 nanosheets onto the surface of bowl-like mesoporous PDA nanoparticles via in-situ oxidative growth method. The obtained PDA@MnO2 nanomotor shows effective diffusion coefficient of 25.0 µm2/s under NIR light irradiation (808 nm, 3 W/cm2). Under the NIR light irradiation, the PDA@MnO2 nanomotor displays the enhanced removal efficiency of Pb2+ and methylene blue (MB), with the adsorption capacity of 176 mg/g for Pb2+ and 81 mg/g for MB. Our developed dual-propelled PDA@MnO2 nanomotor may have a promising potential for removal application of multiple pollutants.

Facile synthesis of layered superparamagnetic Fe3O4-MoS2 nanosheets on chitosan for efficient removal of chromium and ciprofloxacin from aqueous solutions

The discharge of toxic metal ions and pharmaceutical pollutants has become a global issue. This work evaluated the efficiency of the hydrothermally synthesized superparamagnetic Fe3O4-MoS2 nanosheets and its fabrication with chitosan (Fe3O4-MoS2@CS) to remove Cr(VI) and ciprofloxacin (CIP) from simulated wastewater. These nanohybrid materials are characterized by SEM-Mapping, Raman, TEM, XRD, XPS, zeta potential, FTIR, and BET analyses. The affinity and selectivity of Fe3O4-MoS2@CS nanomaterial towards a mixture of Cr(VI), As(II), Pb(II), and Cd(II) metal ions from synthetic solution is studied through ICP-MS at trace levels. The distribution coefficient (Kd) for Cr(VI) (1.2 × 104 mL/g) is higher than the other metal ions, which reveals high selectivity of Fe3O4-MoS2@CS. The Fe3O4-MoS2@CS has also displayed enhanced removal efficiency for ciprofloxacin (emerging contaminant) from synthetic solutions. The Fe3O4-MoS2 and Fe3O4-MoS2@CS nanomaterials possess high saturation magnetization values of 68.00 emu/g and 59 emu/g, respectively. The adsorption process of Cr(VI) highly depends upon the solution pH, and the adsorption isotherm is followed by the Langmuir isotherm model. The kinetics of sorption is followed well by the pseudo-second-order model. The adsorption mechanism is assumed due to functional group complexation, and electrostatic interactions. Fe3O4-MoS2@CS has displayed maximum sorption capacity for Cr(VI) (175.4 mg g−1) and CIP (190.7 mg g−1) respectively. Fe3O4-MoS2@CS has been used in practical applications to remove Cr(VI) (97 %) and CIP (62 %) from real simulated wastewater. The enhanced adsorption efficiency and excellent magnetic recyclability of Fe3O4-MoS2@CS nanohybrid material make it a promising sustainable adsorbent for clean production and wastewater treatment.

Co-substrate promoting the biodegradation of refractory DOM in semi-coking wastewater: DOM evolution and microbial community

Semi-coking wastewater treatment has become a difficult issue because of its complexity, heterogeneity and toxicity. In this study, co-metabolism with ethanol or sodium acetate as co-substrates was applied to improve the biological degradation of refractory dissolved organic matter (DOM) in semi-coking wastewater. Kinetic model simulation results indicated that both co-substrates addition improved COD removal efficiency and biodegradation rate. Excitation-emission matrix (EEM) spectroscopy and size exclusion chromatography with organic carbon detector (SEC-OCD) analysis were applied to evaluate the DOM biodegradation in terms of fluorescence and molecular weight (MW). Although co-substrates resulted in a comparable enhanced removal efficiency of protein-like and humic-like fluorophores, there are distinct differences in their specific protein-like fluorescent peaks (Peak C1&C2). Ethanol addition was more conducive to the removal of humic substance with apparent molecular weight (AMW) ranging from 1.1 kDa to 20 kDa. Acetate addition resulted in higher removal of building blocks of humic substances (BB, AMW 0.45–1.1 kDa) and proteinaceous biopolymers (BP, AMW >20 kDa). Co-metabolism triggered the shift of microbial community structure and metabolic functions. Using co-occurrence network analysis, nine keystone genera were identified, which maintained the functional stability of bacterial community responding to organic toxicants stress. LefSe analysis elucidated that the potential major genera involved in refractory organics biodegradation with acetate addition were Stenotrophomonas (40.3%) and Pseudomonas (21.2%), while Pseudoxanthomonas (10.4%) with ethanol addition. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt2) analysis showed that benzoate, styrene, xylene and naphthalene degradation pathway were enhanced by acetate addition as compared to ethanol.

Regulating the Anodic Catalytic Selectivity in Electro-Fenton Process for Enhanced Pollutant Removal

Owing to its simplicity, remarkable mineralization efficiency, and eco-friendly characteristics, the electron-Fenton (EF)-based advanced oxidation process is recognized as an effective technology to remove refractory organic pollutants. However, this technology is still limited by a narrow pH operation and low current efficiency due to the unsatisfactory activity and concomitant competing reactions on the electrodes. Herein, we demonstrate the versatility of regulating the water oxidation selectivity on the anode in the EF system to enhance the removal efficiency for pollutants with broadened pH range and improved current efficiency. With a homemade iron–carbon-based catalyst (Fe/C) as a cathode, commercial TiO2 (two-electron water oxidation) or RuO2 (four-electron water oxidation) as the anode, and rhodamine B (RhB) as the pollutant, the degradation efficiency values of both TiO2–Fe/C and RuO2–Fe/C are higher than that of conventional Pt–Fe/C with/without aeration, respectively. Specifically, the removal ratio for RhB in TiO2–Fe/C could reach 84.3% and 67.1% within 3 min at pH 3.0 and 7.0 with O2 aeration as compared to that of 56.7% and 45.6% for the Pt–Fe/C system. Without O2 aeration, the removal ratio for RhB in RuO2–Fe/C could reach 67.1% and 45.3% within 3 min at pH 3.0 and 7.0, while the values were 51.6% and 21.2% for the Pt–Fe/C. Furthermore, the H2O2 accumulation indicated that the two-electron water oxidation on the TiO2 could further increase the total concentration of H2O2. The four-electron water oxidation on the RuO2 could supplement O2 for the cathodic reduction to maintain the concentration of H2O2 during the electrolysis, leading to enhanced removal efficiency. Herein, based on the regulation of the water oxidation reaction in the anode, we propose an anodic optimized strategy to upgrade the EF-related processes.

Activated Hollow and Solid Carbon Spheres for Enhanced Removal Efficiency of Pharmaceutical Pollutants and Heavy Metals in Water

Activated Hollow and Solid Carbon Spheres for Enhanced Removal Efficiency of Pharmaceutical Pollutants and Heavy Metals in Water

Egg-derived porous plasma modified clay composite for wastewater remediation.

Clays are often envisaged as an alternative to activated carbon for wastewater pollutant adsorption. However, conclusive results have only been obtained for clays heavily chemically modified. In this study, a greener approach is proposed to improve the retention capacity of clays. It consists in mixing clay (C) with eggshell (ES) and calcine, and then exposing to gliding arc plasma (ESC-800/PL). The resulting materials were characterized by nitrogen physisorption, FTIR, XRD, TGA/DTG, and point of zero charge analyses. The preparation gives porous platelet agglomerates resulting from the kaolinite-metakaolinite transition, thereby increasing their internal specific surface area and capacity to retain pollutants. This granular distribution is kept stable by partial pozzolanic reactions avoiding deagglomeration. The specific surface area and total pore volume increased respectively from 14 m2g-1 and 0.049 cm3g-1 to 89 m2g-1 and 0.061 cm3g-1 leading to an enhanced removal efficiency of Fast Green and Orange G dyes from polluted water. The maximum adsorption capacity occurred at 298K attaining values of 32.34 and 14.78mgg-1 for OG and FG, respectively. The pH plays a crucial role in the maximum sorption of dyes, and the experimental data were successfully adjusted to pseudo-first-order kinetic and Liu isotherm model.

Biochar enhances the biotransformation of organic micropollutants (OMPs) in an anaerobic membrane bioreactor treating sewage

The removal of emerging organic micropollutants (OMPs) in anaerobic membrane bioreactors (AnMBRs) has garnered considerable attention owing to the rapid development of AnMBR technology and the increased environmental risk caused by OMP discharge. We investigated the removal efficiency of 22 typical OMPs from sewage being treated in an AnMBR, and implemented and evaluated an upgrading strategy by adding biochar. The average removal efficiency of OMPs was only 76.8% due to hydrophilic OMPs containing electron-withdrawing groups (ketoprofen, ibuprofen, diclofenac, and carbamazepine) being poorly removed. Biochar addition (5.0 g/L) promoted the removal of recalcitrant OMPs by 45%, leading to an enhanced removal efficiency of 88.7%. Although biochar has a high adsorption capacity to different OMPs, the biotransformation rather than sorption removal efficiency of 13 of the 22 OMPs was largely enhanced, suggesting that adsorption-biotransformation was the main approach by which biochar enhances the OMP removal. Biotransformation test and microbial analysis revealed that the enrichment of species (Flavobacterium, Massilia, Acinetobacter, and Cloacibacterium) involved in OMP biotransformation on biochar contributed largely to the enhanced biotransformation removal efficiency of OMPs. In this way, the enhanced electron transfer activity and syntrophic metabolism between hydrogenotrophic methanogens and species that oxidize acetate to H2/CO2 on biochar jointly contributed to the stable CH4 production and OMP biotransformation. This study provides a promising strategy to enhance the OMP removal in AnMBRs and improves our understanding of the underlying mechanism of biochar-amended OMP removal in anaerobic treatment systems.

Simultaneous removal of Sb(III) and Sb(V) from mining wastewater by reduced graphene oxide/bimetallic nanoparticles.

Antimony (Sb) contamination is a significant environmental issue in mining impacted areas, where the use of nanomaterials to remove such metalloid species has attracted much research attention. In this study, the simultaneous removal of Sb(III) and Sb(V) was investigated using a reduced graphene oxide/Fe/Ni (rGO-Fe/Ni NPs) composite. Compared to rGO alone the composite exhibited enhanced removal efficiency. For rGO-Fe/Ni NPs the maximum Sb(III) and Sb(V) adsorption capacities were 2.00 and 1.41 mg·g-1, respectively, compared to 1.70 and 1.02 mg·g-1 for Sb(III) and Sb(V), respectively, when using rGO only. This indicated that Fe/Ni enhanced the simultaneous removal of Sb(III) and Sb(V). Advanced characterization via SEM and XPS before and after exposure to Sb indicated that both Sb(III) and Sb(V) were adsorbed on to the surface of rGO-Fe/Ni NPs, followed by oxidation of Sb(III) to Sb(V). Adsorption and oxidation kinetics both conformed to pseudo-second order models, where the mechanism for the simultaneous removal of Sb(III) and Sb(V) by rGO-Fe/Ni NPs involved a combination of both adsorption and oxidation. Moreover, the practical adsorption capacity of rGO-Fe/Ni was not limited to Sb, since in a real mining wastewater; containing a mixture of metal(loid)s, while rGO-Fe/Ni exhibited a Sb adsorption capacity of 1.59 mg·g-1, it also exhibited similar adsorption capacities for As (2.61 mg·g-1), Pb (2.41 mg·g-1), and Cd (1.25 mg·g-1). The composite was also highly reusable with a removal efficiency for Sb(III) as high as 72.7% after 4 cycles of use. Thus, rGO-Fe/Ni NPs has significant potential for the practical removal of Sb species and other heavy metal(loid)s in mining impacted wastewaters.

Analytical modeling and interpretation of ultrasound-assisted adsorption mechanism of fuchsine dye on MgZnFeO nanocomposites

An efficient co-precipitation followed by ultrasonication process is used for the synthesis of trimetallic MgZnFeO nanocomposites (MZFONCs) and further characterized by FE-SEM, FT-IR, XRD, EDX, etc. spectroscopic techniques. The adsorption process is applied for the removal of toxic cationic Basic Fuchsine (BF) dye using batch experiments. To enhance removal efficiency, the effect of deviation in parameters including shaking time; adsorbent dose; pH; etc. are studied. Q max obtained by Langmuir is found to be 250 mg/g for BF on the MZFONCs surface, at pH = 6.5; 40 min of agitation time, and a small dose of nanoparticles. The best match for the adsorption of BF on MZFONCs is a double-layer method which also describes the adsorption mechanism. The ‘n’ parameter value (0.507–0.628) is obtained from the statistical physics model, which shows mixed-orientation type adsorption of BF molecules on MZFONCs adsorbents. The calculated energies for BF dye adsorption are found to be less than 30 KJ/mol, hence implying an endothermic and physical adsorption mechanism.

Numerical Investigation of Covid-19 Infection Spread Expelled from Cough in an Isolation Ward Under Different Air Distribution Strategies

COVID-19 is a severe and rapidly spreading respiratory disease that can be transmitted through airborne particles, emitted from cough. This study investigated the influence of underfloor air distribution (UFAD) and overhead air distribution on the diffusion of the coughed particles emitted from two infected patients in an isolation ward. Additionally, the study examined the performance of mounting retractable covers around the exhausts on minimizing the dispersion of the particles. A coupled Eulerian-Lagrangian approach is adopted by using a discrete random walk model. The effect of Brownian force, drag force with Cunningham slip correction factor, turbulence dispersion, Rosin-Rammler, and the breakup is considered in the respiratory airborne coughed particles simulation. The model has a good agreement with the experimental data. The results show that overhead air distribution (case 1) disperses the particles faster to the occupied zone due to the strong mixing between downward inlet airflow and indoor air accompanied by infectious particles. The usage of retractable covers (case 2) significantly minimized the diffusion of the particles inside the ward and their residence time. The particles quantity drops by 53, 98.62, and 99.94 % at 2.0, 10.0, and 120.0 s, respectively, compared to case 1. Case 2 shows the best efficient protection and inhaled air quality for the HCW in all the walking areas inside the room. The upward inlet air in underfloor air distribution (case 3) keeps particles floating for a while at a higher level near the ceiling exhausts, enhancing removal efficiency. Also, it has a slower lateral dispersion of the particles than in case 1. Underfloor air distribution minimized the number of particles by 30.0 % at 120.0 s, compared to overhead air distribution. Inlet air location significantly affects the diffusion of infectious particles in the indoor environment.

NiCo2O4/BiOCl/Bi24O31Br10 ternary Z-scheme heterojunction enhance peroxymonosulfate activation under visible light: Catalyst synthesis and reaction mechanism

The Z-scheme heterostructure for photocatalyst can effectively prolong the lifetime of photogenerated carriers and retain a higher conduction/valence band position, promoting the synergistic coupling of photocatalysis and peroxymonosulfate (PMS) activation. In order to fully utilize the luminous energy and realize the efficient activation of PMS, this work achieved successful construction of NiCo2O4/BiOCl/Bi24O31Br10 ternary Z-scheme heterojunction by simultaneously synthesizing BiOCl and NiCo2O4 with NiCl2 and CoCl2 as the precursors. The intercalated BiOCl could serve as a carrier migration ladder to further achieve the spatial separation of electron-hole pairs, so that the oxidation and reduction processes separately occurred in different regions. Compared with the reported catalysts, the as-prepared composites exhibited the enhanced removal efficiency for tetracycline hydrochloride (TCH) in the visible light/PMS system, with a degradation efficiency of 85.30% in 2 min, and possessed good stability. Z-scheme heterojunction was shown to be beneficial for maximizing the superiority of photo-assisted Fenton-like reaction system. The experimental and characterization results confirmed that both non-radicals (1O2) and radicals (SO5•− and SO4•−) were involved in the reaction process and the SO5•− generated by the oxidation of PMS played a crucial role in the TCH degradation. The possible reaction mechanism was finally proposed. This study provided new insight into the Z-scheme heterostructure to promote the photo-assisted Fenton-like reaction.

A holistic performance assessment of duct-type electrostatic precipitators

Epidemiological surveys have shown a significant association between indoor airborne particle exposure and adverse health effects. Duct-type electrostatic precipitators (ESPs) are effective in controlling airborne particles in buildings. Although several studies have examined the initial performance of duct-type ESPs, there are no comprehensive data on the holistic performance of commercially available ESPs. In addition, there are no published comparisons of the performance of ESPs with and without dielectric coatings considering the impact of dust loading and washing. In this study, laboratory tests were conducted to determine the holistic performance including initial, dust-loaded, and postwashing filtration efficiencies and ozone emission rates of ESPs with and without dielectric coatings. ESPs with dielectric coatings showed enhanced removal efficiency of submicron particles, with overall efficiencies comparable to those of F7 filters and 85% lower energy consumption. The removal efficiency of the ESP with dielectric coatings was superior to those of ESPs without dielectric coatings, but the higher energy consumption of the former led to slightly lower comprehensive performance. The filtration efficiency for submicron particles differed most between the two types of ESPs and was more suitable for evaluating their performance. The ozone emission rates were almost 2–7 times higher for ESPs without dielectric coatings than for the ESP with a dielectric coating (5.9 ± 2.2 mg/h). Based on the initial comprehensive quality factors of the ESPs, the maximum reductions caused by dust loading and washing were 55.3% and 17.5%, respectively. This study demonstrates the importance of considering multiple criteria when evaluating the performance of duct-type ESPs.

Removal of toxic heavy metals using genetically engineered microbes: Molecular tools, risk assessment and management strategies

The direct release of industrial effluent into the water and other anthropogenic activities causes water pollution. Heavy metal ions are the primary contaminant in the industrial effluents which are exceptionally toxic at low concentrations, terribly disturb the endurance equilibrium of activities in the eco-system and be remarkably hazardous to human health. Different conventional treatment methodologies were utilized for the removal of toxic pollutants from the contaminated water which has several drawbacks such as cost-ineffective and lower efficiency. Recently, genetically modified micro-organisms (GMMs) stand-out for the removal of toxic heavy metals are viewed as an economically plausible and environmentally safe technique. GMMs are microorganisms whose genetic material has been changed utilizing genetic engineering techniques that exhibit enhanced removal efficiency in comparison with the other treatment methodologies. The present review comments the GMMs such as bacteria, algae and fungi and their potential for the removal of toxic heavy metals. This review provides current aspects of different advanced molecular tools which have been used to manipulate micro-organisms through genetic expression for the breakdown of metal compounds in polluted areas. The strategies, major limitations and challenges for genetic engineering of micro-organisms have been reviewed. The current review investigates the approaches working on utilizing genetically modified micro-organisms and effective removal techniques.

Biochar-supported nanosized zero-valent iron (nZVI/BC) composites for removal of nitro and chlorinated contaminants

• Specific use of nZVI/BC for reduction and oxidation of nitro and chlorinated contaminants. • Synthesis, characterization and removal efficiency of nZVI/BC are summarized. • BC as support for nZVI and EDA shuttle takes part in organic contaminants removal. • Redox action of Fe 2+ /Fe 3+ , generated from nZVI, takes part in contaminants removal. • Cost, environmental implications, and prospects of nZVI/BC in decontamination. Organic, particularly nitro and chlorinated, contaminants are of great concern in ecosystem for their contribution to environmental problems worldwide. Nitro contaminants are mostly explosives in nature and harmful to ecosystem, and polychlorinated contaminants are main water pollution cause. Nanosized zero-valent iron (nZVI) could remove and degrade organic contaminants through chemical reduction and activated oxidation. To address short-term activity and agglomeration concerns of nZVI, biochar (BC)-supported nZVI (nZVI/BC) composite could be a feasible choice for practical reductive and oxidative removal of nitro and chlorinated contaminants. Carbonaceous BC has been successfully applied in removing contaminants from water and soil, but few research results led to less operation success due to low removal efficiency. Thus, BC and nZVI could compensate for one another’s shortcomings, and the synergistic features of nZVI/BC are beneficial to interaction with contaminants and enhanced removal efficiency. The purpose of this study is a comprehensive overview of nZVI/BC synthesis, characterization, and specified application for nitro and chlorinated contaminants removal. This review focuses, relates, and evaluates literature dedicated to nitro and chlorinated contaminants in the environment, their distribution and adverse effects, nZVI/BC synthesis and characterization, effect of influencing factors during remediation process, aging, and reusability of nZVI/BC on contaminants removal, and outcomes of reductive and oxidative degradation mechanisms. Also, it overviews cost and environmental implications of nZVI/BC synthesis and contaminant remediation processes. Finally, this review ends with future research prospects of nZVI/BC applications in progressive environmental remediation.

Simultaneous reduction and sequestration of hexavalent chromium by magnetic β-Cyclodextrin stabilized Fe3S4

In this study, β-Cyclodextrin (CD) modified Fe3S4 nanomaterials were synthesized by a one-step facile strategy and investigated for the removal of Cr(VI). The resulted CD-Fe3S4 exhibited enhanced removal efficiency toward Cr(VI) than bared Fe3S4 with a maximum capacity of 220.26 mg·g-1 as the molar ratio of CD-to-Fe3S4 at 0.2. The effective performance of CD-Fe3S4 toward Cr(VI) could well maintain under oxic conditions and a wide pH range of aqueous solution. A high selectivity for Cr(VI) was achieved in the presence of coexisting cations and anions. More significantly, a single treatment step of CD-Fe3S4 effectively removed chromium from actual electroplating wastewater to the detection limit of 0.004 mg·L-1 that far below the WHO limitation of Cr (VI) (<0.05 mg·L-1) combing with the rapid magnetic separation without adjusting the pH value of wastewater at 7. The effective removal of Cr (VI) by CD-Fe3S4 involved a complex process of surface adsorption/reduction, and solution homogenous reduction and subsequent sequestration of Cr(III) achieving the effective removal of aqueous total Cr. The superior Cr (VI) removal capability and facial separation of CD-Fe3S4 attained its prominent potential application as an effective material for the Cr(VI) removal.

Adsorption mechanism study of multinuclear metal coordination cluster Zn5 for anionic dyes congo red and methyl orange: Experiment and molecular simulation

This study aimed to investigate the adsorption behaviors of congo red (CR) and methyl orange (MO) on the coordination cluster Zn5(H2Ln)6(NO3)4 (Zn5, H3Ln = 1,2-bis-(benzo[d]imidazol-2-yl)-ethenol). Due to multinuclear assembly, multinuclear Zn5 possessed higher electrostatic potential and exhibited 3-fold enhancement in removal efficiency, compared with mononuclear Zn (Zn(H3L)2, H4L = 1,2-bis-(benzo[d]imidazol-2-yl)-1,2-ethanediol). The infrared and X-ray photoelectron spectroscopy and the electrostatic potential analysis indicated that the adsorption mechanism was electrostatic interaction and ion exchange interaction. The adsorption kinetics followed both the pseudo first-order and Bangham models. The pore system analysis and Bangham model suggested that CR and MO could diffuse in the snakelike pores of Zn5. The adsorption isotherms complied with the Langmuir isotherm model, and the maximum adsorption capacities for CR and MO are 166.91 and 100.78 mg/g at room temperature. The adsorption process was spontaneous and endothermic, driven by the entropy increase. Based on this research, the multinuclear coordination clusters can be suggested as potential adsorbents for the removal of anionic dyes.

Triethanolamine modification produces ultra-permeable nanofiltration membrane with enhanced removal efficiency of heavy metal ions

Nanofiltration membranes are attractive for the removal of the heavy metal ions but limited by the trade-off between permeance and solute rejection. Membrane permeance is closely correlated to hydrophilicity and solute rejection is closely linked to size exclusion and Donnan electrostatic repulsion. Here, triethanolamine was employed as a crosslinking agent to prepare modified polyethyleneimine/trimesoyl chloride nanofiltration (PEI/TMC NF) membranes with excellent separation performance for the removal of heavy metal ions from contaminated water. The permeance was more than 2 times increased from 6.4 Lm −2 h −1 bar −1 to 13.6 Lm −2 h −1 bar −1 due to the increase in membrane hydrophilicity resulting from the incorporation of hydrophilic hydroxyl groups on the membrane surface; the rejection of metals was high (around 97% rejection for Zn 2+ , Cd 2+ , Ni 2+ , Cu 2+ ; around 92% rejection for Pb 2+ ) due to the enhancement of positive charges on the membrane surface resulting from lone pair electrons of N elements on triethanolamine and the decrease in pore size of the membrane (MWCO from 280 Da to 220 Da). The short-term filtration test (72 h) of the simulated wastewater with various metal ions shows that the prepared membranes have excellent stability for industrial application. Unlike the traditional superior permeance achieved by ultrathin membranes with weakness and defects, the triethanolamine modification endows the pristine PEI-TMC NF membranes with superior performance without the complicated methods for thickness reduction. • Two times water permeance increased without decreasing membrane thickness. • Improved hydrophilicity due to the incorporation of hydroxyl groups on membrane surface. • Enhanced charges density due to the grafting quaternary ammonium (N+) on triethanolamine. • Fabricated NFM-1 membranes with outstanding rejection performance of heavy metal ions.

Mechanism and process of sulfamethoxazole decomposition with persulfate activated by pulse dielectric barrier discharge plasma

The present study focused on pulse dielectric barrier discharge (DBD) plasma activated persulfate (PS) for sulfamethoxazole (SMZ) degradation in water. The results showed that PS addition could enhance removal efficiency of SMZ in pulse DBD plasma system. The highest removal efficiency, kinetic constant and energy efficiency reached 93.4%, 0.084 min−1 and 0.353 g/kWh respectively with the PS dosage of 40:1 and input power of 85 W. With increase of imput power and pulse frequency, the removal efficiency of SMZ was also increased. The removal efficiency was firstly enhanced and then declined as raising duty cycle and liquid flow rate. SMZ degradation was promoted in alkaline solution conditions. Active species including ·OH, e-, ·O2–, 1O2 and ·SO- 4 play a certain role in the degradation of SMZ. The decline of O3 and enhancement of ·OH and H2O2 were found after PS addition. In process of SMZ degradation, the overall conductivity increased but pH decreased. PS addition accelerated the removal of COD and TOC. The degradation process was explored by UV–Vis spectra, three-dimensional fluorescence and LC-MS. Three degradation pathways were deduced based on the indentified intermediates. SMZ degradation in the system was considered as a toxicity-attenuation process. The water matrix including Cl-, HCO3–, SO42- and HA have some impact on SMZ degradation. This study presented that pulse DBD plasma could activate PS efficiently, which finally improved pollutant removal efficiency and energy utilization.