Tannic acid modified SnS2 lamellar membranes with enhanced antifouling properties for dye wastewater treatment

Application of polymeric ferric sulfate combined with cross-frequency magnetic field in the printing and dyeing wastewater treatment

Micellar enhanced ultrafiltration in the treatment of dye wastewater: Fundamentals, state-of-the-art and future perspectives

An integrated system comprising coagulation, hydrolysis acidification, and multilevel contact oxidation was evaluated to make the dyeing effluent meet discharge standards. A new spiral biological carrier was first used in the treatment of dyeing wastewater. The chemical oxygen demand (COD), color, and biodegradability index (i.e., biological oxygen demand (BOD)/COD) of raw dyeing wastewater were 5051 mg/L, 404 times, and 0.29, respectively. During coagulation, 80% COD and 64% color were reduced with 80 mg/L polyaluminum chloride as coagulant. The hydraulic retention time (HRT) of subsequent hydrolysis acidification and multilevel contact oxidation was determined as 23.6 h. After the integrated treatment of coagulation–hydrolysis acidification–multilevel contact oxidation, COD, BOD, color, and ammonia removal efficiencies reached 98%, 99%, 92%, and 99%, respectively. The effluent met Class 1 discharge standards (GB4287-2012). In particular, the new spiral biological carriers used in multilevel contact oxidation led to significant total nitrogen (TN) removal. When the HRT of multilevel contact oxidation process was 16.4 h, the TN removal efficiency was 73.3%. The spiral carriers can provide an anoxic microenvironment in the inner part because of their high strength spiral structure, which facilitates the transformation from nitrate to nitrogen gas through simultaneous nitrification and denitrification. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 339–345, 2015

The anaerobic baffled reactor (ABR) is an anaerobic bioreactor that uses baffles to separate the working area into multiple reaction zones. The ABR-microbial fuel cell (MFC) reactor was constructed by embedding MFC in each reaction zone of the ABR. Its degradation of azo dye type (acid mordant red) wastewater and microbial power generation performance were investigated. For different electrode area ratios, the best enhanced treatment and electrical energy output of the coupled system was achieved with an anode/cathode area ratio of 1:1. Compared with the electrode area ratio of 2:1 and 1:2, the power density increased by 82.5% and 80.6%, and the Coulomb efficiency increased by 133.3% and 64.7%. In addition, the best enhanced treatment of printing and dyeing wastewater was achieved by ABR-MFC at 1:1. At a dye concentration of 200 mg/L and a sucrose concentration of 1000 mg/L, the coupled system obtained a COD removal of 92.85% and a chromaticity removal of 96.2%, which achieved a relative COD and chromaticity removal improvement of 1.82% and 2.64%, respectively, relative to the ABR. Scanning electron microscopy (SEM) observation of the electrodes at 1:1 revealed that more microorganisms were attached to the anode surface of the coupled system, the particle size of the granular sludge within the system was larger, and the UV scanning pattern showed lower dye concentration in the water. In conclusion, the microbial fuel cell enhanced anaerobic treatment of dyeing wastewater was the most effective when the electrode area ratio was 1:1, and the best electrical energy output was obtained at the same time. ABR-MFC provides a new idea for the enhanced treatment of dyeing wastewater and electrical energy production.

Removal of dye contamination from wastewater is crucial for protecting human health and the environment, and adsorption is considered an effective removal method. In addition, agricultural residues are attractive for use as adsorbents for the adsorption due to their renewability. Therefore, the present work aimed to develop silica xerogel from rice husk (agricultural residue in rice production) into an adsorbent for dye wastewater treatment. In the xerogel synthesis, a non-toxic organic acid (citric acid) was used instead of a toxic inorganic acid for leaching and precipitation steps to lower the environmental impact of the process. It was found that the obtained silica xerogel has physical properties such as a surface area and pore volume, comparable with silica xerogels in other literature. When applying it in the dye (methylene blue) wastewater treatment, the obtained silica xerogel showed better adsorption capacity than unprocessed silica at all studied conditions, i.e. various times, pH and initial concentration. The maximum adsorption capacity of the xerogel and unprocessed silica were 103.45 and 61.78 mg/g, respectively. This indicates the benefit of silica xerogel with low environmental impact when applied in dye wastewater treatment. The adsorption isotherms and kinetic for both types of silica were also conducted. It was found that the adsorption process of methylene blue on the silica fitted the Langmuir adsorption isotherm and followed the pseudo-second-order kinetic model. This provides valuable information for optimizing the operating parameters for best performance in a given situation.

Synthesis method, antibacterial and photocatalytic activity of ZnO nanoparticles for azo dyes in wastewater treatment: A review

Removal of methylene blue(MB) from aqueous solution by a new polyoxometalate-based metal-organic framework composite(POM@MOF) was systematically explored in batch tests. The chemical structure and surface properties of the composite were characterized by means of FTIR, XRD, EDS, N2 adsorption-desorption isotherms and zeta potential measurements. The results showed that MB adsorption onto H6P2Mo15W3O62@Cu3(BTC)2 highly depended on initial solution pH, which was mainly related to the electrostatic attraction between negatively charged composite surface and positively charged MB molecules. Thus, the improved adsorption performance of H6P2Mo15W3O62@Cu3(BTC)2 can be attributed to the modification of H6P2Mo15W3O62 resulting in its higher electronegative charge than Cu3(BTC)2. The thermodynamic parameters indicated that the adsorption was spontaneous and exothermic process. The isotherm obtained fitted the Langmuir model and the maximum adsorption capacity of the composite at 30 oC was 77.22 mg/g. All the results illustrated that H6P2Mo15W3O62@Cu3(BTC)2 composite can effectively and selectively remove cationic organic pollutants, represented by MB, implying the promising application of designing a novel adsorbent polyoxometalate-based metal-organic frameworks in treatment of dye wastewater.

Using ·OH from Fenton’s reagent, the strong oxidation treatment of methylene blue dye wastewater can destruct the chromophore in organic compounds, and yield CO2, H2O and small molecule inorganic compounds by oxidative degradation finally. The influence of Fenton's reagent dosage, initial pH, and reaction time on the degradation effect was studied. The experimental results show that the decolorization rate of 100mL 20mg/L methylene blue dye wastewater can achieve 96% in the conditions of 0.02g FeSO4·7H2O, 1mL 30% H2O2, initial pH at 3.0 ~4.0, reaction time is 30 min, at room temperature. This treatment of dye wastewater is easy to operate and with good effect.

Wastewater from industrial dyeing has become a major problem in modern water treatment, owing to their complex structures, bio-refractory, anti-oxidation, anti-photolysis, and strong heat stability. Thus, treatment of dye wastewater has attracted the attention of researchers. The focus of this work is the removal effect of 2,4,6-trimercaptotriazine (TMT) and polyacrylamide (PAM) independent action and synergistic effect on malachite green (MG). The removal effect with different factors, such as the dosage of TMT or PAM, pH value, and temperature, were investigated, and the removal mechanism is discussed. The results show that the decolour treatment of MG dye wastewater can achieve the ideal effect by the synergy of TMT and PAM.

Direct contact membrane distillation for the treatment of industrial dyeing wastewater and characteristic pollutants

Use and applications of metal-organic frameworks (MOF) in dye adsorption: Review

To reclaim and utilize wastepaper (WP), a WP/acrylamide double-network hydrogel (WP/PAM) was prepared to transform WP into efficient adsorbent for heavy metals and dye wastewater treatment. The structure and properties of the WP/PAM were characterized systematically by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), swelling performance (SR), Fourier transform infrared spectrum (FTIR), and X-ray photoelectron spectroscopy (XPS). Batch experiments showed that the adsorption process of Cu(ii) and MB followed the pseudo-second-order kinetic model and the Langmuir model. The maximum adsorption capacities of the WP/PAM for Cu(ii) and MB were 142.2 mg g−1 and 1714.5 mg g−1, respectively. The adsorption mechanism of Cu(ii) on the WP/PAM was related to ion exchange and complexation, while MB adsorption was driven by hydrogen bonding and electrostatic interaction. Besides, the WP/PAM performed well in treating simulated wastewater. The regeneration test indicated that the WP/PAM could be successfully reused after 6 cycles. This work provided an alternative choice for the recycling of WP and produced a potential adsorbent for the dye and heavy metals wastewater treatment.

The presence of high concentrations of inorganic salts significantly challenges the treatment of dye wastewater. This study employed the high-gravity ozonation technology to degrade the Acid Red 73 (AR73) dye wastewater with high-salinity. A high-gravity device – a rotating packed bed (RPB), was used as the reactor for the treatment of the AR73 wastewater with ozone. The impact of inorganic salts, including K2HPO4, (NH4)2SO4, Na2CO3, NaHCO3, and Na2SO4 with concentrations up to 50 g/L, on the treatment effect of the wastewater in the RPB/O3 process was investigated. The liquid detention phenomena in the RPB were also explored to enhance the treatment of the AR73 wastewater. It was found that with the AR73 concentration of 300 mg/L and Na2SO4 concentration of 30 g/L in the wastewater, the optimal treatment effect was achieved at the detained liquid volume of 150 mL, with the ozone absorption, AR73 and COD removal rates reaching 75.7%, 91.3%, and 32.4%, respectively, representing increases of 103.5%, 34.9%, and 106.3% compared to those without liquid detention. The RPB/O3/liquid detention process provides an efficient method for the treatment of high-salinity dye wastewater.

Environmental context Full mineralisation of synthetic azo dyes in industrial wastewater is a tough job for traditional wastewater treatment technologies. There is an urgent need for the development of both sustainable and environmentally friendly technology capable of fully mineralising these azo compounds. We show that solar-driven advanced oxidation processes are capable of completely mineralising azo compounds with high utilisation of solar energy. Abstract Mineralisation of synthetic azo dyes in industrial wastewater is an energy-intensive process in treatment technology. The Solar Thermal Electrochemical Process for advanced oxidation processes (STEP-AOPs) utilises solar energy and electricity for the activation and electrooxidation of organic pollutants to harmless, small and non-toxic molecules with no other energy consumption. Based on molecular structure and chemistry, the STEP-AOPs for the treatment of azo dyes in wastewater, as exemplified with a typical azo dye, methyl orange, is reported for the first time. Thermodynamic calculations of the temperature-dependent potentials of methyl orange demonstrate that Gibbs free energy decreased by 161 kJ mol–1 and the potential decreased by 0.019 V with an increase of temperature from 20 to 80 °C, which indicates that the drop in both energy and potential specifically fits the STEP-AOPs technique. Experimental results showed that the STEP-AOPs achieved a total organic carbon (TOC) removal of 95.6 % for methyl orange. The TOC removal rate improved by 39.8 % and the unit TOC electricity consumption decreased by 53.8 % at 80 °C compared with conventional methods (20 °C). The mineralisation mechanism for methyl orange was a gradual shortening of the molecular chain through cleavage of the azo bond, breakdown of the benzene ring and formation of inorganic small molecules susceptible to be oxidised to non-toxic small molecules, and carbon dioxide via STEP-AOPs. The evidence shows that the STEP-AOPs is capable of mineralising azo compounds completely.

Treatment of industrial dye wastewater and pharmaceutical residue wastewater by advanced oxidation processes and its combination with nanocatalysts: A review