Stable Removal Rate Research Articles

Impact of iron-modified fillers on enhancing water purification performance and mitigating greenhouse effect in constructed wetlands

ABSTRACT Iron is gradually being introduced into constructed wetlands (CWs) to enhance the removal of pollutants due to its active chemical properties and ability to participate in various reactions, but its effectiveness in greenhouse effect control needs to be studied. In this study, three CWs were established to evaluate the effect of iron scraps and iron-carbon as substrates on pollutants removal and greenhouse gas (GHG) emissions, and the corresponding mechanisms were explored through analysis of microbial characteristics. The results showed that iron scraps and iron – carbon are effective in enhancing the effluent quality of CWs. Iron-carbon exhibited notable efficacy in removing nitrate nitrogen (NO3 --N) and chemical oxygen demand (COD), achieving stable removal rates of 98.46% and 84.89%, respectively. Iron scraps had advantages in promoting the removal of ammonia nitrogen (NH4 +-N) and total nitrogen (TN), with removal rates of 43.73% and 71.56%, respectively. The emission fluxes of nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) had temporal variability, always peaking in the early phases of operation. While iron scraps and iron-carbon effectively reduced the average emission flux of N2O and CO2, they simultaneously increased the average emission flux of CH4 (from 0.2349–2.2698 and 1.1956mg/m2/h, respectively). From the perspective of reducing global warming potential (GWP), iron – carbon had superior performance (from 146.2548–86.7447 mg/m2/h). In addition, the greenhouse gas emission flux was closely related to the microbial community structure in CWs, particularly with a more pronounced response observed in N2O emissions.

Optimized Design of Modular Constructed Wetland for Treating Rural Black–Odorous Water

In recent years, the phenomenon of black–odorous water has occurred frequently, and constructed wetlands have been widely used as an effective means of treating black–odorous water. In order to achieve the goal of low-carbon and high-efficiency long-term clean-up of black–odorous water, the modular constructed wetland system was optimized in this study. The optimized modular constructed wetland consisted of aeration, denitrification, and phosphorus removal, of which the denitrification module was a sulfur–iron autotrophic denitrification unit and the phosphorus removal module was a polyaluminum chloride composite filler phosphorus-removal unit. Experimental findings indicated that modular systems with layout ratios of 1:3:1 (A) and 1:2:2 (B) exhibit outstanding performance in remediating contaminants from black–odorous water. Notably, system B demonstrated superior treatment efficiency. Under conditions of high pollution loading, system B consistently achieved stable removal rates for COD (95.79%), TN (91.74%), NH4+-N (95.17%), and TP (82.21%). The combination of along-track changes and high-throughput sequencing results showed that the synergies among the units did not produce negative effects during the purification process, and each unit realized its predefined function. Changes in the substrate and internal environment of the wetland units caused changes in the microbial populations, and the unique microbial community structure of the units ensured that they were effective in removing different pollutants.

Rapid, Massive, and Green Synthesis of Polyoxometalate-Based Metal-Organic Frameworks to Fabricate POMOF/PAN Nanofiber Membranes for Selective Filtration of Cationic Dyes.

Developing high-efficiency membrane materials for the rapid removal of organic dyes is crucial but remains a challenge. Polyoxometalates (POMs) clusters with anionic structures are promising candidates for the removal of cationic dyes via electrostatic interactions. However, their shortcomings, such as their solubility and inability to be mass-produced, hinder their application in water pollution treatment. Here, we propose a simple and green strategy utilizing the room temperature stirring method to mass produce nanoscale polyoxometalate-based metal-organic frameworks (POMOFs) with porous rhomboid-shaped dodecahedral and hexagonal prism structures. The products were labeled as POMOF1 (POMOF-PW12) and POMOF2 (POMOF-PMo12). Subsequently, a series of x wt% POMOF1/PAN (x = 0, 3, 5, and 10) nanofiber membranes (NFMs) were prepared using electrospinning technology, where polyacrylonitrile (PAN) acts as a "glue" molecule facilitating the bonding of POMOF1 nanoparticles. The as-prepared samples were comprehensively characterized and exhibited obvious water stability, as well as rapid selective adsorption filtration performance towards cationic dyes. The 5 wt% POMOF1/PAN NFM possessed the highest removal efficiency of 96.7% for RhB, 95.8% for MB, and 86.4% for CV dyes, which realized the selective separation over 95% of positively charged dyes from the mixed solution. The adsorption mechanism was explained using FT-IR, SEM, Zeta potential, and adsorption kinetics model, which proved that separation was determined via electrostatic interaction, hydrogen bonding, and π-π interactions. Moreover, the POMOF1/PAN membrane presented an outstanding recoverable and stable removal rate after four cycles. This study provides a new direction for the systematic design and manufacture of membrane separation materials with outstanding properties for contaminant removal.

A novel vertical immobilized photocatalytic membrane reactor based on Bi2WO6-g-C3N4/PVDF for enhanced removal of atrazine, anti-fouling performance and long-term stability

The high efficiency, anti-fouling performance and long-term stability of photocatalytic membrane reactors (PMRs) are critical in practical applications. Here, three flat-sheet immobilized PMRs based on Bi2WO6-g-C3N4/polyvinylidene fluoride (PVDF) photocatalytic membrane were constructed and compared for atrazine (ATZ) degradation under simulated sunlight. The photocatalytic removal rate of ATZ by the vertical PMRs was remarkable, at 78.98% in 6 h, and had a stable removal rate (about 65%) under continuous flow mode (18 h). Additionally, the reactor presented superior reusability and long-term stability with an ATZ removal rate of 65% even after at least 6 cycles in continuous flow mode. By filtering bovine serum albumin (BSA), humic acid (HA) and sodium alginate (SA) under simulated solar irradiation, it demonstrated good anti-fouling ability, which was further proved by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. The degradation pathway and evolution of the intermediates were proposed by HPLC-QTOF-MS/MS and DFT calculations. The PMR in this work has great potential in the water treatment industry.

A GO-based biocatalytic membrane prepared by one-step pressure-assisted self-assembly for micropollutants removal

Biocatalytic membranes are a green and effective option for the removal of micropollutants (MPs) from water. The effective immobilization of enzyme together with facial fabrication of membrane is constantly required. Herein, a biocatalytic membrane was prepared by one-step pressure-assisted self-assembly of graphene oxide (GO), polyethyleneimine (PEI) and laccase (Lac) on the surface of hydrolyzed polyacrylonitrile (HPAN) membrane. The physical and chemical property of membranes, and the immobilization of laccase were characterized. Under optimal conditions, the biocatalytic membrane has a bisphenol A (BPA) removal rate of 95.3%, and the rejection for dyes can be higher than 97% with salts rejection of less than 23% and pure water permeance of 207.4 LMH/bar. Meanwhile, GO-PEI-Lac membrane retained stable removal rate under a wide pH range and feed BPA concentrations. The membrane can also remove various phenolic MPs. In addition, the GO-PEI-Lac membrane retained more than 80% removal rate after 6 cycles. Overall, this study opens up a convenient avenue for the facial fabrication of high-efficient biocatalytic membranes for MPs removal.

Flexible Fiber Conditioner for Fine Conditioning of Polishing Pad and its Evaluation in Chemical Mechanical Polishing: Verification of SUS-FFC on Soft Urethane Foam Pad and Proposal of PEEK-FFC

Polishing pad conditioning is essential for achieving stable chemical mechanical polishing (CMP). While diamond disk conditioners (DDCs) are often applied, flexible fiber conditioners (FFCs) have been proposed as a new conditioning tool. FFCs are intended for roughening the pad surface appropriately by bundling fine wire fibers. Our previous study demonstrated the fine conditioning characteristics of FFCs for a hard urethane foam pad. In this study, the conditioning characteristics of an FFC are compared with those of a DDC. First, we evaluate the conditioning performance of an FFC using SUS fibers on a soft urethane foam pad. The result indicates that on a soft pad, the SUS-FFC can restore the pad surface asperities more finely, as confirmed via the stabilized number of contact points based on contact image and luminance value distribution analyses. Subsequently, for a metal-contamination-free FFC process intended for semiconductor CMP, we develop an FFC fabricated using polyether ether ketone (PEEK) and verify its performance via the CMP test of a silicon oxide film. It is shown that the hard pad can be conditioned using the developed PEEK-FFC; this implies that a stable removal rate can be realized immediately after pad break-in conditioning.

Simultaneous adsorption and oxidation of Sb(III) from water by the pH-sensitive superabsorbent polymer hydrogel incorporated with Fe-Mn binary oxides composite

In this work, the superabsorbent polymer hydrogel (SPH) of Poly(potassium acrylate-co-acrylamide (PPAA)) incorporated with Fe-Mn binary oxides (FMBOs) was synthesized and used for the removal of Sb(III) from water. Characterization analysis proved that FMBO3 was successfully encapsulated into the SPH. The Fe/Mn oxide species in the composite SPH comprised FeO(OH), Fe2O3, MnO(OH), and MnO2. The functional groups including N–H, –OH, carboxy as well as Fe atoms were confirmed adsorption sites through ligand exchange and inner-sphere complexes formation. Mn oxides can partially oxidize Sb(III) to Sb(V). Compared with the pseudo-first-order model, the pseudo-second-order model could better describe the adsorption kinetics. And the swelling degree of the composite SPH had a positive impact on the removal rate. The Langmuir-Freundlich model was the most suitable isotherm model to analyze the experimental data. According to thermodynamic parameters, the adsorption process was a spontaneous exothermic reaction. The maximum adsorption capacity of the composite SPH for Sb(III) could be up to 105.59 mg/g at 288 K. In addition, a stable removal rate can be achieved over a wide pH range of 3–10, with little metal leaching even under acidic conditions. Furthermore, coexisting ions and DOM displayed an insignificant influence on the adsorption of Sb(III).

Efficient removal of a low concentration of Pb(II), Fe(III) and Cu(II) from simulated drinking water by co-immobilization between low-dosages of metal-resistant/adapted fungus Penicillium janthinillum and graphene oxide and activated carbon

Drinking water safety cannot be overemphasized. Filamentous fungi have many excellent features for metal removal. Both graphene oxide (GO) and activated carbon (AC) are conventional metal adsorbents, but they are not suitable for large-scale use due to high cost. In this study, a low dosage of conidia (2.0 × 104 conidia/mL) of metal-resistant/adapted filamentous fungus Penicillium janthinillum strain GXCR were co-immobilized with a low dosage of 0.5 mg/L GO or 0.5 mg/L AC by embedding in 2% polyvinyl alcohol (PVA)-3% sodium alginate (SA), generating six types of microbead adsorbents (MBAs) to remove metals from a low concentration of either single metal (100 mg/L) or mixed metals (100 mg/L each) of Pb (II), Fe (III) and Cu (II) in drinking water. Fungus GXCR-containing MBAs had higher specific surface areas (SSAs), better mesoporous structures, and a higher removal rate (85–98.99%) of single or mixed metals. Singl-metal adsorptions of MBAs were almost unaffected by temperature changes. MBAs showed a stable removal rate of 87–94% during four cycles of adsorption-desorption of single metal. Single-metal adsorptions were well described by multiple models of Freundlich isotherm with constant values of 0.21–0.432, Langmuir isotherm with constant values of 0.037–0.17, Pseudo-fist-order, Pseudo-second-order, and intra-particle diffusion (IPD). In conclusion, co-immobilization between GXCR, GO and AC can make metal removal more efficient. Adsorption capacity is increased with SSAs but not in the same proportion. Single-metal adsorptions involve multiple mechanisms of monolayer and multilayer adsorptions, external mass transfer, and IPD. IPD is important but not the only one rate-controlling step for single-metal adsorptions.

Experimental Study on a Closed-Cycle Humidification and Dehumidification System for Treating Wastewater Containing High Concentrations of Inorganic Salts and Organic Matter

Industrial wastewater contains high concentrations of inorganic salts and organic matter. This experiment studied a system for treating wastewater containing high concentrations of inorganic salts and organic matter. The setup consists of a closed-cycle humidification and dehumidification system and a filter press. Chemical wastewater was used as the treatment solution, and the treatment performance of the system was tested and analyzed. The system effectively reduced the chemical oxygen demand (COD), electric conductivity (EC), total nitrogen (TN), and ammonia nitrogen (NH4-N) in the wastewater and, at the same time, dehydrated sludge was obtained through a filter press. The system maintains a stable removal rate of each index (COD, EC, TN, and NH4-N) in wastewater and can remove inorganic salts and organic matter from wastewater. The system can successfully treat industrial wastewater containing high concentrations of inorganic salts and organic matter.

Phosphorus Release and Adsorption Properties of Polyurethane-Biochar Crosslinked Material as a Filter Additive in Bioretention Systems.

Bioretention systems are frequently employed in stormwater treatment to reduce phosphorus pollution and prevent eutrophication. To enhance their efficiency, filter additives are required but the currently used traditional materials cannot meet the primary requirements of excellent hydraulic properties as well as outstanding release and adsorption capacities at the same time. In this research, a polyurethane-biochar crosslinked material was produced by mixing the hardwood biochar (HB) with polyurethane to improve the performance of traditional filter additives. Through basic parameter tests, the saturated water content of polyurethane-biochar crosslinked material (PCB) was doubled and the permeability coefficient of PCB increased by two orders of magnitude. Due to the polyurethane, the leaching speed of phosphorus slowed down in the batching experiments and fewer metal cations leached. Moreover, PCB could adsorb 93–206 mg/kg PO43− at a typical PO43− concentration in stormwater runoff, 1.32–1.58 times more than HB, during isothermal adsorption experiments. In the simulating column experiments, weaker hydropower reduced the PO43− leaching quantities of PCB and had a stable removal rate of 93.84% in phosphate treatment. This study demonstrates the potential use of PCB as a filter additive in a bioretention system to achieve hydraulic goals and improve phosphate adsorption capacities.

Removal Rates of NOx, SOx, and Fine Dust Particles in Textile Fabrics Coated with Zeolite and Coconut Shell Activated Carbon

An effective dipping method for coating of textile fabrics with porous materials is proposed on the basis of the use of epoxy solution consisted of resins, crosslinkers, and dilution solutions. The removal rates of nitrogen oxides (NOx), sulfur oxides (SOx), and fine dust particles in the coated textile fabrics are accessed. The textile fabrics made of polyester are used to effectively reduce fine dust particles through static electricity. Zeolite and coconut shell activated carbon are used as porous material to reduce SOx and NOx, respectively. The effects of the epoxy content and dilution solution types on the SOx removal rate of textile fabrics coated with zeolite are evaluated to determine the optimum coating conditions. In addition, the effects of external environmental conditions, such as washing and freeze thawing, on the SOx and NOx removal rates of the textile fabrics coated with porous materials using the optimum coating conditions are examined. The test results show that the SOx removal rate of textile fabrics coated with zeolite decreases with the increase in the epoxy content. The decrease is 2.9 times larger for textile fabrics coated using deionized water than those coated using isopropyl alcohol. After one wash, the SOx removal rate decreases dramatically. However, the decrease is reduced by 16% when the epoxy content ratio is increased by 0.5%. The effects of washing and freeze thawing on the SOx and NOx removal rates of textile fabrics coated using the deionized water diluted with the epoxy content ratio of 2% are minimal. Consequently, to maintain stable SOx and NOx removal rates under external environmental conditions such as washing and freeze thawing, 98% deionized water dilution and 2% epoxy content ratio are required for the optimum coating of textile fabrics with zeolite and coconut shell activated carbon.

A novel strategy for enhancing the performance of membranes for dyes separation: Embedding PAA@UiO-66-NH2 between graphene oxide sheets

A composite membrane based on a novel strategy was prepared which using graphene oxide (GO), UiO-66-NH2 and polyacrylic acid (PAA) as basic materials on the surface of nylon membrane by vacuum filtration self-assembly. The structure of the composite membrane was made of graphene oxide as vertical separation layer, the PAA@UiO-66-NH2 (PAA@UiO) embedding between GO as horizontal capture material. The PAA@UiO-66-NH2/GO (PAA@UiO/GO) membrane was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Compared with the GO membrane, PAA@UiO/GO membrane combined the effects of GO, UiO-66-NH2 and PAA, which significantly enhances the separation performance of dye wastewater. In particular, the PAA@UiO/GO membrane can achieve complete removal of MB, RB and CR while the fluxes during filtration process can reach about 100 L∙m-2∙h-1. At the same time, PAA@UiO/GO membrane almost retained stable removal rate on all dyes under extreme pH and ionic strength conditions. In addition, after 10 cycles of experiments, PAA@UiO/GO membrane retained a removal rate and a flux more than 95% and 85 L∙m-2∙h-1for all dyes, respectively. Compared to a composite membrane based on intercalation, the unique structure of PAA@UiO/GO membrane with a large number of adsorption sites and screening structures, resulting a better removal rate for dyes. Furthermore, PAA@UiO/GO membrane has a great potential in practical applications and a solution to balance trade-off effect.

Environmentally friendly electrostatically driven self-assembled LDH/GO/PVDF composite membrane for water treatment

In this contribution, an environmentally friendly electrostatically driven self-assembled layered double hydroxide (LDH)/graphene oxide (GO)/polyvinylidene fluoride (PVDF) composite membrane was prepared and evaluated. The composite membrane was prepared based on the electrostatic self-assembly between positively charged LDH and negatively charged GO, then above composite was loaded on the PVDF membrane substrate by vacuum suction filtration. The preparation process does not contain organic matter, which was very environmentally friendly. The properties of the composite membrane were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy. The above characterizations showed that the addition of LDH can increase the layer spacing of the GO sheets, the hydrophilicity of the composite membrane, and the removal rates of Cu2+ and methylene blue (MB). More importantly, the composite membrane has excellent stability in water and maintains a stable removal rate after long-term filtration. And no significant changes occur even after being left in the ultrasonic bath for a while. In general, the LDH/GO/PVDF composite membrane prepared in this study has a great application value and prospect in the water treatment and opens up a new path in improving membrane performance.

Stabilization of Removal Rate in Small Tool Polishing of Glass Lenses

The demand for improving the image quality of cameras has increased significantly, especially in industrial fields such as broadcasting, on-vehicle, security, factory automation, and medicine. The surface of glass lenses as a key component of cameras is formed and finished by polishing using small tools. The existing polishing technologies, however, exhibit serious problems including an unstable material removal rate over time. In our previous work, the mechanism of time variation in material removal rate was clarified. Based on the findings, a vibration-assisted polishing method using polishing pads containing titanium dioxide particles was developed for improving the stability of the material removal rate with the accumulated polishing time. Our experiments revealed that the proposed polishing method suppressed the time variation significantly in the material removal rate. The developed polishing pads, however, possessed a short life because of their poor wear resistance; as such, they could not be applied to the mass-production process of lenses. In this study, we applied the vibration-assisted polishing method to the polishing process using commercial polishing pads that exhibit sufficient wear resistance for practical use. To investigate the effect of vibration on the stability of the material removal rate, polishing experiments and the observation of slurry flow on the surface of the polishing pads during the vibration-assisted polishing process were conducted. Based on the findings, a new polishing method utilizing a large-amplitude high-frequency vibration applied to the polishing pressure was developed. In addition, a new polishing method utilizing the overhang of a polishing pad, where the polishing pad was moved to hang over the edge of the workpiece for incorporating periodic dressing processes of the polishing pad surface during the polishing process, was also developed. Our polishing experiments revealed that both the proposed polishing methods improved the stability of the material removal rate significantly over the course of the polishing process.

Water Quality and Three-Dimensional Fluorescence of Stormwater Runoff from Lined Bioretention Field Cells

Bioretention cells have become one of the most popular devices in urban stormwater runoff management for their high efficiency in reducing runoff volume and pollution loads. However, bioretention cells are unstable in nutrient pollutant removal, as is verified by many cases, especially at low temperatures. Dissolved organic matters (DOMs) plays an important role in denitrification, but the three-dimensional fluorescence characteristics of stormwater runoff in bioretention field cells are poorly understood, so to improve the performance of bioretention cells in nutrient pollutants control, the authors determined that it was necessary to clarify the characteristics of three-dimensional fluorescence of stormwater runoff from bioretention cells and explain their relationship to water quality. To be applicable to urban landuse in mountainous cities, two field lined bioretention cells were constructed, and, from March to April in 2017, while temperatures were still low, water quality and three-dimensional fluorescence of stormwater runoff were analyzed during low rainfall intensity precipitation events. Analysis results showed that the effluent pollutant concentrations had low fluctuation after purification by the bioretention cells, and both cells showed relatively stable removal rates for NH4+-N and total phosphorus (TP; i. e., 78.38%-95.03% and 72.04%-76.04%, respectively). Analysis of fluorescence spectra showed that the DOMs in the runoff from the two cells was mostly made up of protein and humic substances, mainly of biological origin or aquatic bacterial metabolites. Both cells performed well in the removal of protein at I, protein at Ⅱ and fulvic acid (i. e., the removal rates could reach 57.33%-61.30%, 29.82%-31.28%, and 35.55%-43.16% respectively). Correlation analyses between water quality and DOM showed that total Nitrogen (TN), TP and total organic carbon (TOC) were positively correlated with the protein content in runoff from the biorentention cells, while NO3--N and NH4+-N were negatively correlated with protein content. Meanwhile, TN was negatively correlated with DOMs in regions Ⅳ and Ⅴ of the cells.

Microbial Community Enhances Biodegradation of Bisphenol A Through Selection of Sphingomonadaceae.

Bisphenol A (BPA) is a common ingredient in plastic wares and epoxy resins that are essential for our daily life. Despite the obvious benefits, BPA may act as an environmental endocrine disruptor, causing metabolic, reproductive, and/or developmental consequences and diseases in humans and other organisms. Although previous studies have yielded progress toward the microbial breakdown of BPA, the work has primarily been focused on pure cultures rather than complex microbial communities. In this study, we examined microbial communities in bioreactors that control the fate of BPA at various levels (up to 5000μgL-1). Microbial communities rapidly increased removal rates of 500-5000μgL-1 BPA from 23-29 to 89-99% during the first 2weeks of the acclimation period, after which > 90% stable removal rates were maintained over 3months. Biochemical assays demonstrated that BPA was removed by biodegradation, rather than other abiotic removal routes (e.g., adsorption and volatilization). The 16S rRNA gene-based community analysis revealed that 50-5000μgL-1 of BPA exposure systematically selected for three Sphingomonadaceae species (Sphingobium, Novosphingobium, and Sphingopyxis). The Sphingomonadaceae-enriched communities acclimated to BPA showed a 7.0-LgVSS-1day-1 BPA degradation rate constant, which is comparable to that (4.1-6.3) of Sphingomonadaceae isolates and is higher than other potential BPA degraders. Taken together, our results advanced the understanding of how microbial communities acclimate to environmentally relevant levels of BPA, gradually enhancing BPA degradation via selective enrichment of a few Sphingomonadaceae populations with higher BPA metabolic activity.

Achieving stable removal rate in polishing with small tools

The demand for cameras with high image quality has led to their increased use by consumers and in industrial applications such as broadcasting, on-vehicle, security, and medicine. Glass lenses as key devices in cameras are finished with small polishing tools. However, the existing polishing technologies have serious problems, including an unstable material removal rate over time. To investigate the variation mechanism of the material removal rate, glass-polishing experiments were conducted. Based on our findings, we proposed a vibration-assisted polishing method using newly developed polishing pads containing titanium dioxide particles. Our experiments revealed that the proposed polishing method significantly improved the stability of the material removal rate.

Microbial Community Composition in a Simultaneous Nitrification and Denitrification Bioreactor for Domestic Wastewater Treatment

Traditional domestic wastewater treatments rely on aerobic processes followed by anaerobic processes. The aerobic step in which ammonium and organic carbon are oxidized, calls for large oxygen input, while the anaerobic process often requires extra carbon input. The challenge of synchronizing both processes is to maintain an active nitrifiers sludge under low dissolved oxygen (DO) condition. In this study, a membrane bioreactor was established and operated stable with low DO of 0.1-0.4 mg L-1. Chemical indicators were determined daily, and bacterial community was checked by qPCR and 16S rDNA sequencing every month. After 2 months incubation, the bioreactor reached to a stable removal rate of total nitrogen around 50% and total organic carbon around 90% with the retaining time of 12 h. The sludge showed enrichment of low DO nitrifiers (Nitrosomonadaceae, Chitinophagaceae, and Nitrospiraceae) which were different from sludge in other regular wastewater treatment plants with aerobic and anaerobic cycles.

Study of cyanide wastewater treatment by dispersion supported liquid membrane using trioctylamine and kerosene as liquid membrane.

A certain amount of cyanide is present in wastewater of various industrial processes, such as wet extraction of gold, coal processing, electroplating and other industries. In this work, an experimental study regarding transport of cyanide through a dispersion supported liquid membrane was performed. A model was established to describe the reaction and transport of CN(I) in the supported liquid membrane and the mass transfer kinetics equations were deduced. Through mass transfer kinetic equation it was derived that, when the carrier concentration was under certain conditions, there was a linear relationship between the reciprocal of the permeability coefficient of CN(I) (1/Pc) and n-th power of the concentration of H+ (cnH+), and the parameters Δa(δa/da) and Δo(δ0/d0) could be obtained from the slope and intercept of the straight line. Then the diffusion coefficient do and the diffusion layer thickness δo of the phase interface between the feed phase and membrane phase could be calculated. Factors affecting migration of CN(I) were analyzed, and the stable removal rate of CN(I) was more than 90% with carrier concentration (%TOA) of 2%, feed phase pH of 4, initial CN(I) concentration of 30 mg/L, stirring time of 1 hour, volume ratio of membrane solution to NaOH solution of 2:1, strip phase concentration of 2 mol/L. The results showed that the overall mass transfer rate increased first and then decreased with an increase of TOA concentration, organic-to-strip volume ratio, and strip concentration. Furthermore, the transport percentage of CN(I) was increased, the stability of membrane was enhanced, and the lifetime of the membrane was extended.

Removal of methylene blue using photocatalytic slurry reactor coupled with ceramic membrane cross-flow filtration process

By combining ceramic membrane cross-flow filtration process with photocatalytic reaction, a photocatalytic membrane reactor was designed. The reactor was simulated, and it was confirmed that it was a continuous stirred tank reactor. Experiment results indicated that, using a ceramic membrane with mean pore size of 0·1 µm, slurry TiO2 particles with mean size of 0·27 µm could be perfectly separated and recycled in the system, and the stable removal rate of methylene blue was more than 95% with TiO2 loading of 0·5 g L−1, reaction temperature of 45°C, filtration pressure of 0·5 kg cm−2 and cross-flow velocity of 3·3 m s−1.