Purification Of Dye Wastewater Research Articles

Hydrothermal and photocatalytic synergistic pretreatment to improve the full utilization of corn stalk

In this study, the hydrothermal and photocatalytic synergistic pretreatment for improving the full component utilization of corn stalk based on lignin first biorefining was employed to generate carbohydrates and obtain modified lignin. The results showed that the highest lignin removal ratio (40.70 %) and cellulose retention ratio (92.64 %) were obtained due to the smallest energy gap (6.05 eV) and the largest penetration distance (1.73 Å) between GVL and the lignin. And the yield of carbohydrates increased from 1.95 % to 58.17 % after hydrothermal pretreatment at 180 ℃. Furthermore, the modified lignin enhanced the flocculation effect, resulting in the increase of the removal of safranine-T by 6 times. In addition, the chemical and physical properties of modified lignin were studied and the mechanism of photocatalysis modification was explored. The research provides a new pretreatment method for the utilization of biomass and simultaneously achieves carbohydrate enrichment in bio-oil and purification of dye wastewater.

Ferrous-Oxalate-Modified Aramid Nanofibers Heterogeneous Fenton Catalyst for Methylene Blue Degradation

The heterogeneous Fenton system has drawn great attention in recent years due to its effective degradation of polluted water capability without limitation of the pH range and avoiding excess ferric hydroxide sludge. Therefore, simple chemical precipitation and vacuum filtration method for manufacturing the heterogeneous Fenton aramid nanofibers (ANFs)/ferrous oxalate (FeC2O4) composite membrane catalysts with excellent degradation of methylene blue (MB) is reported in the study. The morphology and structure of materials synthesized were characterized by scanning electron microscope (SEM), X-ray energy spectrum analysis (EDS), infrared spectrometer (FTIR), and X-ray diffraction (XRD) equipment. The 10 ppm MB degradation efficiency of composite catalyst and ferrous oxalate (FeC2O4) within 15 min were 94.5% and 91.6%, respectively. The content of methylene blue was measured by a UV-Vis spectrophotometer. Moreover, the dye degradation efficiency still could achieve 92% after five cycles, indicating the composite catalyst with excellent chemical stability and reusability. Simultaneously, the composite catalyst membrane can degrade not only MB but also rhodamine B (RB), orange II (O II), and methyl orange (MO). This study represents a new avenue for the fabrication of heterogeneous Fenton catalysts and will contribute to dye wastewater purification, especially in the degradation of methylene blue.

A high-flux polydopamine/reduced graphene oxide/MOF-5 composite membrane via a mussel-inspired method for dye wastewater purification

A high-flux polydopamine/reduced graphene oxide/MOF-5 composite membrane via a mussel-inspired method for dye wastewater purification

Facile synthesis of porous isotype heterojunction g-C3N4 for enhanced photocatalytic degradation of RhB under visible light

To improve the comprehensive photocatalytic performance of g-C3N4, a facile co-polycondensation method was applied to synthesize porous isotype heterojunction g-C3N4 using urea and melamine as precursors. The microstructure of as-prepared samples was revealed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption desorption test, Fourier-transform infrared spectra, X-ray photoelectron spectroscopy, and thermogravimetry. The product yield and thermal stability of the isotype g-C3N4 was improved. Photocatalytic performance of all samples was evaluated by photodegradation of Rhodamine B under visible light. The results show that U3M1 sample (with urea-to-melamine ratio of 3:1) exhibits the highest photocatalytic efficiency, and the corresponding apparent rate constant is around 1.4 and 6.7 folds than that of U1M0 (with pure urea) and U0M1 (with pure melamine), respectively. The enhanced photocatalytic activity can be attributed to the hierarchically porous isotype heterojunction structure, which not only improves the charge separation efficiency, but also reduces the electron-hole recombination. In addition, the porous isotype heterojunction g-C3N4 displays excellent reusability after suffering 4 cyclic tests. This work provides a feasible method for preparing g-C3N4 with high photocatalytic efficiency, and promotes the application of g-C3N4 in the purification of dye wastewater.

Engineering a concordant microenvironment with air-liquid-solid interface to promote electrochemical H2O2 generation and wastewater purification

Electroreduction of O2 to H2O2 provides an appealing route for both renewable energy storage and wastewater purification. Although grand endeavors are devoted into synthesizing high-performance electrocatalysts, the understanding and engineering of local microenvironment around reactive sites are also critical. Herein, a concordant gas/liquid microenvironment with plentiful air–liquid-solid interfaces is constructed and evaluated, which not only mediates the harmonious transport of O2, H+ and electron (especially reducing the O2 diffusion layer thickness and raising O2 local concentration to accelerate O2 transport), but also induces massive highly active triphase boundary sites for high-rate H2O2 electro-generation. Consequently, even under natural air diffusion, the cathode with the polytetrafluoroethylene proportion of 20% achieves a preeminent H2O2 productivity (40.7 mg h−1 cm−2 at 100 mA cm−2, corresponding to the maximum H2O2 concentration of 813.8 mg L-1) with superior current efficiency (64.2%). Long-term electrolysis stability and reusability indicate the practicability of the air-breathing cathode without the energy-intensive external aeration. Efficient purification of dye wastewater by the modified cathode meets the expectation, showing its huge potential in environmental protection. This work deeply elucidates the effect mechanism of a concordant gas/liquid microenvironment with abundant air–liquid-solid interfaces, which has considerable guiding significance for similar gas-involving electrocatalysis.

Developing polysulfone-based mixed matrix membrane containing hydrazone-linked covalent organic frameworks towards dye wastewater purification

The shortage of water resources and the increased demand for clean water warrant focused investigations on wastewater treatment. In this regard, mixed matrix membranes (MMMs) have been introduced as economic and efficient tools for removing contaminants from wastewater. The current study deals with the synthesis of a hydrazone-linked covalent organic framework (Hz-TFPTZ-COF) and its incorporation into polysulfone (PSf)/ poly N-vinylpyrrolidone (PVP) matrix to obtain Hz-TFPTZ@PSf/PVP MMM containing different concentrations of Hz-TFPTZ-COF (0–1 wt%). The synthesized Hz-TFPTZ-COF and the prepared MMMs were fully characterized using various analytical techniques. The negative surface charge of Hz-TFPTZ-COF made it a good candidate for removing cationic dyes. Moreover, the effect of Hz-TFPTZ-COF loading on the mechanical properties, porosity, pure water permeability (PWP), and dye rejection of the prepared MMMs was investigated. Hz-TFPTZ-COF concentration as low as 1.0 wt% in the MMM formulation yielded a PWP as high as 94.69 L. m−2. h−1. bar−1 and dye rejection of 92% and 88% for Basic Blue 41 and Methyl Violet, respectively. In addition, the tensile strength of the prepared MMMs was increased from 2.26 to 3.43 MPa. Overall, incorporating the Hz-TFPTZ-COF into PSf/PVP polymeric matrix affords a MMM with superior performance in the purification of cationic dye wastewater.

Honeycomb-like cork activated carbon with ultra-high adsorption capacity for anionic, cationic and mixed dye: Preparation, performance and mechanism

Herein, the cork activated carbon (CAC) with excellent adsorption performance for cationic dye, anionic dye, and mixed dye was obtained by a two-step pyrolysis method. The CAC exhibits a fluffy honeycomb structure consisted of porous carbon nanosheets (100–200 nm), ultra-high specific surface area (3402.68 m2/g), and well-developed hierarchical porous structure, which offers a great deal of adsorption sites and transport channels to dye molecules. The adsorption process of all the dyes onto CAC is better described by Langmuir isotherm model and pseudo-2nd-order kinetic model. The CAC shows ultra-high adsorption capacity for methylene blue (1283.99 mg/g), rhodamine B (4067.57 mg/g), methyl orange (2666.2 mg/g), and congo red (8920.61 mg/g), with an extremely low equilibrium adsorption time (∼10 min). Collectively, this study demonstrated the potential of converting waste cork into high value-added adsorbent for the efficient purification of dye wastewater.

Efficient degradation of toxic mixed dyes through peroxymonosulfate activation by copper/iron nanoparticles loaded on 3D carbon: Synthesis, characterizations, and mechanism

Exploitation of heterogeneous catalysts with high activity, stability and reusability gains increasing worldwide attention due to the tremendous demand for purification of dye wastewater. Copper/iron bimetallic catalysts have been proven to be powerful for persulfate activation to generate reactive radical species. Copper/iron nanoparticles loaded onto porous carbon (Cu/FeNPs@PC) was innovatively designed and used as catalyst for peroxymonosulfate (PMS) activation. Cu/FeNPs@PC manifests high catalytic activity for dye degradation over a wide pH range (4.0–10.0). Under conditions of 0.2 g/L catalyst, PMS 0.15 g/L and pH 4.8, nearly complete degradation (98.4%) of Rhodamine B occurs after 18 min. The rate constant is between 0.0946 and 0.1911 min−1 depending on initial solution pH. Mixed dyes can be efficiently degraded verified by UV–vis spectra and color variation of dye solution. Cu/FeNPs@PC has good stability, magnetism, and reusability for recycling. A synergistic effect of promoting Cu2+/Cu+ and Fe3+/Fe2+ cycle is probability ascribed to the enhanced catalytic activity. The mechanism of catalytic degradation of dyes involves radical species (SO4-• and •OH) and non-radical pathways including 1O2 and mediated electron transfer. This work provides insights into rational design of binary metal catalysts that apply to treatment of dye wastewater.

Construction of solvent resistance O‐PASS@UiO‐66‐NH2/O‐PASS composite membrane for methylene blue removal

AbstractThe purification of dye wastewater plays a critical role in water pollution treatment. Adsorption is a cheap and effective separation technology but is limited by the reuse of adsorption materials. Ultrafiltration membranes have a relatively high flux but their pores are too large to reject small dye molecules. In this study, negatively charged oxidized poly (arylene sulfide sulfone) (O‐PASS) membrane, NMP pretreatment oxidized O‐PASS (N‐O‐PASS) membrane, and O‐PASS@UiO‐66‐NH2/O‐PASS composite membranes were fabricated to retain cationic methylene blue (MB) from wastewater by combining ultrafiltration and adsorption techniques. The increased porosity of the N‐O‐PASS membrane provides more available adsorption sites for an equilibrium MB adsorption amount of 22.5 (mg g−1) and 100% rejection in the first 10 min during ultrafiltration with a pure water flux of 162.32 (L m−2 h−1 bar−1). Due to the enhanced hydrophilicity and separating property by deposited UiO‐66‐NH2 particles and PASS resin, O‐PASS@UiO‐66‐NH2/O‐PASS composite membrane shows a flux of 170.32 (L m−2 h−1 bar−1) and a 100% MB rejection in 60 min with great reusability. The O‐PASS@UiO‐66‐NH2/O‐PASS composite membrane is a new promising membrane for the removal of dyes from wastewater. Meanwhile, the superior solvent resistance endows it great adaptability in wide applications, especially in harsh conditions.

Preparation of GO/GOH/MOFs ternary blend membrane and its application for enhanced dye wastewater purification

A graphene oxide (GO)/hydroxylated graphene (GOH)/MOFs porous layered cross-flow membrane was constructed using a simple vacuum filtration method. Bimetallic MOFs (FeCuBDC) was inserted into the GO nanosheets to facilitate the expansion of adjacent GO layers in the aqueous solution, which increased the interlayer spacing of the composite films. Furthermore, successful loading of GOH not only increased the interlayer spacing of the composite membrane but also improved the self-cleaning catalytic degradation effect. The blend membrane was further characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM). Loading ratios of FeCuBDC and GOH were optimized and the results showed that the GO0.8/GOH0.2/(FeCuBDC)4 membrane had a water flux 9.5 times higher than GO membrane and 1.43 times higher than GO1/FeCuBDC4 membrane. Importantly, the separation efficiency of the GO0.8/GOH0.2/(FeCuBDC)4 membrane was very high (Rhodamine B(RhB) membrane separation efficiency was 99.98%), and the interception and flux remained almost constant even after seven RhB separation cycles. This membrane can be directly used for the degradation of pollutants through persulfate activation, and showed the high degradation efficiencies of RhB(99.89%) and methylene blue (MB) (99.87%). Overall, the GO/GOH/FeCuBDC porous layered cross-flow membrane exhibited excellent separation performance, stability, and catalytic activity, and can be used as a potential membrane for water purification and environmental protection.

One-step efficient separation of heavy/light oils, dyes and water by simple filtration with a 3D architecture of functional mesh and sisal fiber felt

Producing clean water by the harmless treatment of complex wastewater containing oils and organic pollutants (e.g., dyes) is highly desirable, but the major challenge is the lack of a simple, effective and low-cost way to remove simultaneously heavy oil, light oil and dyes. Here, we designed and constructed a three-dimensional architecture (3D-A) composed of the hydrophilic or hydrophobic functionalized copper mesh (as the upper layer) and the sisal fiber felts (SFs) modified with Mg/Fe-LDH or magnesium silicate (MgSi) (as the bottom layer), and confirmed that clean water was produced through filtering complex wastewater with the 3D-A in one step. For heavy oil/dyes wastewater, the dye solution in it can be trapped by hydrophobic mesh, while heavy oils passed through the mesh. The heavy oils were collected, while the dye solution flows into the light oils/dye mixed solution for further separation. The hydrophilic mesh may trap light oils in light oil/dyes wastewater, and allow dye solution to penetrate the mesh by gravity with a stable high flux [>18000 L/(m2·h)] and high oil–water separation efficiency of 99%. The light oils were collected, while the dye solution flows into the modified SFs layer. The Mg/Fe-LDH modified SFs and MgSi-modified SFs can capture above 99.9% of Congo red (CR) and Methylene blue (MB) dyes, respectively to obtain clean water, and each kilogram of Mg/Fe-LDH@SFs and MgSi@SFs adsorbents can treat 9400 and 18000 kg dye wastewater, respectively. The meshes are very stable and antifouling, and can resist acid and alkaline condition (pH 1 ∼ 13), as well as mechanical scratch. The 3D-A also shows high efficiency in purifying real oily emulsion wastewater from the iron and steel industry to produce clean water, and the used SFs can be easily regenerated for cyclic use in purification of dye wastewater.

A robust and renewable solar steam generator for high concentration dye wastewater purification

An optimized T-shaped Au/ceramic solar steam generator was fabricated, showing good robustness, pH and thermal stability. The blocked generator after long-term purification of high concentration dye wastewater can be regenerated by calcination.

Preparation of Go/Goh/Mofs Ternary Blend Membrane and its Application for Enhanced Dye Wastewater Purification

Preparation of Go/Goh/Mofs Ternary Blend Membrane and its Application for Enhanced Dye Wastewater Purification

High performance GO/MXene/PPS composite filtration membrane for dye wastewater treatment under harsh environmental conditions

As the world continues to develop, it faces increasingly serious environmental problems. For wastewater, membrane separation is widely used as an efficient technology. However, less research has been done for applications in harsh environments. Therefore, we proposed a two-dimensional (2D) composite GO/MXene-PPS (GMS) membrane formed by a simple vacuum self-assembly method. The obtained GMS membrane has a typical lamellar structure, and the composite membrane showed great surface wettability to water and organic solvents, as well as high resistance to harsh environments. The composite membranes allow ultra-fast transport of water molecules to reach a high pure water flux of 45.78 Lm-2h-1bar-1, meanwhile ensuring a high rejection rate of 99.99% for many organic dyes such as MB. In addition, the prepared composite membranes exhibited excellent performance in harsh environments such as strong acids/bases and organic solvents, indicating its potential application in dye wastewater purification treatment.

A novel solar-triggered MIL-125(Ti)/g-C3N4/SA composite aerogel with high catalytic activity for degradation of organic contaminants

• A novel solar-triggered MIL-125(Ti)/g-C 3 N 4 /SA aerogel was prepared. • It exhibited excellent photocatalytic degradation and antibacterial properties. • The removal efficiency of dye wastewater can reach up to 99.3% under visible light. • It has excellent stability and reusability, easily recycled from the wastewater. Sodium alginate (SA) aerogels have shown outstanding potential as regenerative adsorbent materials in the field of wastewater purification. Although SA aerogel adsorption has been demonstrated as a simple and resultful method for removing dyes, it has the limitation that it only transfers or concentrates dyes on the adsorbate, and does not actually degrade them. In this study, a three-dimensional (3D) MIL-125/g-C 3 N 4 /SA (CNTi-125@SA) composite aerogel with visible light photocatalytic activity was achieved for photocatalytic degradation of organic dyes, via in-situ growth, blending and freeze-drying strategy. The results demonstrate that CNTi-125@SA has high catalytic activity for the dyes rhodamine B (RhB), methylene blue (MB) and methyl orange (MO), and the degradation rate can reach up to 99.23%. Impressively, the composite aerogel exhibits excellent antibacterial ability, and the antibacterial rate can reach up to 100% against E. coli . In addition, the developed composite aerogel has excellent reusability and stability, and the degradation efficiency can still reach 85% after seven repeated tests. Owing to their high catalytic activity, excellent antibacterial properties and stability, the CNTi-125@SA composite aerogel can be potentially used in a wide range of dye wastewater purification.

Co-intercalation of TiO2 and LDH to reduce graphene oxide photocatalytic composite membrane for purification of dye wastewater

In this project, the Titanium dioxide nanowire (TiO2Nw) and layered double hydroxide (LDH) were introduced into the reduced graphene oxide (RGO) to make a composite material and then were assembled on the cellulose acetate (CA) membrane into photocatalytic composite membrane (RLT) through vacuum filtration with photocatalytic effect. The photocatalytic composite membrane (RLT) with high permeability and high rejection was constructed. Compared with other ratios of RLT membranes, RLT-0.5 composite membrane had a higher water flux of 432.38 L·m−2h−1bar−1, and the rejection rate of dye were above 99%. In the rejection process of 10 cycles, that the rejection rate and flux of RLT-0.5 composite membrane to methylene blue (MB), malachite green (Mg) and Congo red (CR) were more stable regardless of whether there was light or no light. Of course, the rejection effect was better under light conditions, showing its excellent photocatalytic performance. In conclusion, RLT-0.5 composite membrane had excellent water purification ability and photocatalytic efficiency, which made it have a wide application in water treatment.

Facile Preparation of Cu2S/Cu Mesh For High‐performance Solar Water Evaporation

AbstractSolar vapor generation has attracted tremendous attention as one of the most efficient ways of utilizing solar energy. Compared with bulk heating, interfacial solar steam generation efficiency is high, and the heat loss to the surrounding environment is minimal, which is an eco‐friendly and energy‐efficient way of harvesting solar energy for desalination and wastewater treatment. So it is highly desirable to develop low‐cost and high‐efficiency solar absorbers for practical applications of interfacial solar steam generation. In this work, Cu2S/Cu mesh was prepared by depositing Cu2S nanoparticles on copper mesh by one‐step hydrothermal method, which was used as photothermal conversion material for solar interfacial evaporation. This material owns a high solar absorptivity of 84.01 % within the wavelength range of 0.25–2.5 μm. Under one sun illumination, the evaporation rate is 1.55 kg m−2 h−1 and the solar thermal conversion efficiency reaches 96.9 %. The cycle stability tests showed that the evaporation rate decreased firstly and then was balanced at 1.34 kg m−2 h−1 in 10 cycles. Furthermore, this material can maintain a stable performance of interfacial solar steam generation during desalination of seawater and purification of dye wastewater containing Rhodamine B and Methyl Orange, respectively. This work provides a low‐cost, simple, and efficient preparation method for synthesizing an efficient Cu2S/Cu mesh solar steam evaporation material.

Facile Preparation of a Carbon-Based Hybrid Film for Efficient Solar-Driven Interfacial Water Evaporation.

Solar-driven interfacial water evaporation is one promising technology for seawater desalination and sewage purification because it offers a feasible and sustainable strategy to relieve global water scarcity. Herein, a novel hybrid film composed of recycled carbon soot and poly(vinyl alcohol) is developed by a very simple, green, and highly scalable "salt-assisted" assembling method. The hybrid film possesses characteristics with a porous structure, superhydrophilicity, ∼100% light absorption, and low thermal conductivity, which can effectively convert light into heat under solar illumination. Consequently, the hybrid film can achieve a photothermal conversion efficiency of 91.5% under a stimulated solar irradiation of 1 kW m-2. Furthermore, the hybrid film can be applied for seawater desalination and dye wastewater purification. The findings of our work not only provide a new photothermal platform with high light-to-thermal conversion ability and good reusability but also open a new avenue for the applications of carbon soot-based hybrid films in solar-assisted water evaporation and sewage purification.

TiO2/CTS/ATP adsorbent modification and its application in adsorption-ultrafiltration process for dye wastewater purification.

Industrial dyeing produces highly polluting wastewater and threatens the environment. Effective treatment of dyeing wastewater is a crucial step to prevent toxic chemicals from entering receiving waters. This study aimed to assess a modified attapulgite (ATP)-based adsorbent for dyeing wastewater purification by introducing chitosan (CTS) and titanium dioxide (TiO2) into the adsorbent material named TiO2/CTS/ATP. It was found that after modification, the adsorbent showed a lower hydrophilicity, as demonstrated by an increase in the water contact angle from 9.1° to 42°, which could reduce the water adsorption tendency and potentially facilitate contaminants adherence. The modification also led to a significantly increased specific surface area of 79.111 m2/g from 3.791 m2/g and exhibited more uniform and smaller particle size (reduced from 3.99 to 2.52 μm). When the TiO2/CTS/ATP adsorbent was applied to the adsorption of Congo red solution, the adsorption efficiency was observed to reach to 97.6% at the dosage of 0.5 g/L. Furthermore, the combination of adsorption and ultrafiltration was able to achieve 99% Congo red removal. Adsorption pretreatment prior to the ultrafiltration also enabled to reduce membrane fouling, increased the reversible membrane fouling, and resulted in a considerably lower transmembrane pressure as compared with the direct ultrafiltration filtration system.

Honeycomb-like activated carbon with microporous nanosheets structure prepared from waste biomass cork for highly efficient dye wastewater treatment

Cork, a porous biomass material, is consist of thin-walled hollow prismatic cells arranged into a compact and orderly honeycomb-like structure and could be applied as an adsorption material. Here, cork-activated carbons (CACs) with a fluffy honeycomb-like structure were synthesized by two-step pyrolysis with solid KOH chemical activation to rapidly and efficiently adsorb methylene blue (MB) (maximum wavelength: 664 nm). The structure, morphology and surface functional groups of the CACs were characterized using BET, SEM, and FTIR analysis. The results show that the CACs have a well-developed hierarchical porous structure and an ultra-high specific surface area of 2864.9 m2/g, which would facilitate the efficient diffusion and adsorption of MB molecules onto CACs. MB adsorption performance results show that the CACs have an outstanding maximum MB adsorption capacity (1103.68 mg/g) and fast adsorption kinetics (800 mg/L, 99.8% in 10 min), indicating that CACs possess significant advantages compared with most other adsorbents previously reported. The adsorption mechanism was studied by various kinetic models, isothermal models and thermodynamic models. Langmuir model is the most adapted to describe the adsorption process, indicating that the MB molecules are uniformly adsorbed on CAC’s surface in a single layer. Moreover, MB adsorption by the CACs was an endothermic, spontaneous and randomly increasing adsorption. The regeneration test showed that the uptake of MB onto CACs can still reached 580 mg/g after three adsorption-desorption cycles, demonstrating the excellent reusability of CACs. The continuous adsorption performance of MB onto CACs was evaluated by a packed column test, which further confirmed its potential as an adsorbent for dye wastewater purification.