Adsorptive removal of dye from real textile wastewater using graphene oxide produced via modifications of hummers method

Abstract

This work focused on producing different graphene oxide (GO) samples for further application in the adsorptive removal of dyes from real textile wastewater. Among all conditions tested, the sample produced using KMnO₄ and no sonication bath exhibited the best performance. Before the experiments using wastewater, kinetics and equilibrium of adsorption studies were performed with Methylene Blue (MB) dye. Experimental data showed the isotherm fitted the Freundlich model, and kinetic results fitted the pseudo-second order model. Theoretical q_max was 308.11?mg.g^?1 and over 90% removal of MB was reached in approximately 5?min. Although GO has been widely applied to remove cationic and anionic dyes from water, not many studies have presented GO as an adsorbent for real textile wastewater treatment. In 30?min, GO removed nearly 85% of turbidity and over 60% of color from a real sample, indicating that GO might be an excellent alternative to treat textile wastewater.     

Advanced treatment of textile dyeing wastewater through the combination of moving bed biofilm reactors and ozonation

A four-stage lab-scale treatment system [anaerobic moving bed biofilm reactor (MBBR)-aerobic MBBR-ozonation-aerobic MBBR in series] was investigated to treat textile dyeing wastewater. The MBBRs were operated in a continuous horizontal flow mode. To determine the optimum operating conditions, the effect of hydraulic retention time (HRT) and ozonation time on pollutant removal were analysed by continuous and batch experiments. The optimum operating conditions were found to be 14 h HRT for both anaerobic and no. 1 aerobic MBBRs, 14 min ozonation time and 10 h HRT for no. 2 aerobic MBBR. The average influent concentrations of chemical oxygen demand (COD), suspended solids (SS), ammonia and colour were 824 mg/L, 691 mg/L, 40 mg/L and 165°, respectively. Under these conditions, the average effluent concentrations of COD, SS, ammonia and colour were 47 mg/L, 15.2 mg/L, 5.9 mg/L and 6.1°, respectively, corresponding to total removal efficiencies of 94.3%, 97.8%, 85.3% and 96.3%, respectively. The final effluent could meet the reuse requirements of textile industry. The anaerobic MBBR process improved the biodegradability of the raw wastewater, while the two aerobic MBBRs played an important role in removing COD and ammonia. The ozonation process enhanced the biodegradability of no. 1 aerobic MBBR effluent, and finally, deep treatment was completed in no. 2 aerobic MBBR. The combined process showed a promising potential for treatment of high-strength dyeing wastewater.     

Control of the Fenton process for textile wastewater treatment using artificial neural networks

BACKGROUND: The Fenton process is a popular advanced oxidation process (AOP) for treating textile wastewater. However, high consumption of chemical reagents and high production of sludge are typical problems when using this process and in addition, textile wastewater has wide‐ranging characteristics. Therefore, dynamically regulating the Fenton process is critical to reducing operation costs and enhancing process performance. The artificial neural network (ANN) model has been adopted extensively to optimize wastewater treatment. This study presents a novel Fenton process control strategy using ANN models and oxygen reduction potential (ORP) monitoring to treat two synthetic textile wastewaters containing two common dyes. RESULTS: Experimental results indicated that the ANN models can predict precisely the colour and chemical oxygen demand (COD) removal efficiencies for synthetic textile wastewaters with correlation coefficients (R²) of 0.91–0.99. The proposed control strategy based on these ANN models effectively controls the Fenton process for various effluent colour targets. For treating the RB49 synthetic wastewater to meet the effluent colour targets of 550 and 1500 ADMI units, the required Fe⁺² doses were 13.0–84.3 and 5.5–34.6 mg L^?1 (Fe⁺²/H₂O₂ = 3.0), resulting in average effluent colour values of 520 and 1494 units. On the other hand, an effluent colour target of 550 ADMI units was achieved for RBB synthetic wastewater. The required Fe⁺² doses were 14.6–128.0 mg L^?1; the average effluent colour values were 520 units. CONCLUSION: The Fenton process for textile wastewater treatment was effectively controlled using a control strategy applying the ANN models and ORP monitoring, giving the benefit of chemical cost savings. Copyright © 2009 Society of Chemical Industry     

电絮凝-超滤集成技术处理洗浴废水

采用电絮凝-超滤集成技术处理洗浴废水,实验研究了电极材料、电流密度、电解时间和电导率等因素对电解洗浴废水COD、浊度去除率的影响,并确定了超滤膜的清洗周期和清洗方法.结果表明,电解工艺中Al电极较Fe电极具有更好的处理效果,电絮凝-超滤集成技术对洗浴废水的COD和浊度的去除率分别为85%和95%以上,超滤透过液达到了生活杂用水标准.超滤膜清洗周期为12天,采用化学清洗和水力冲洗相结合的清洗方法可使超滤膜的通量恢复.     

Colour and COD removal from textile effluent by coagulation and advanced oxidation processes

The aim of this study was to compare the performance of coagulation, Fenton's oxidation (Fe²⁺/H₂O₂) and ozonation for the removal of chemical oxygen demand (COD) and colour from biologically pretreated textile wastewater. FeSO₄ and FeCl₃ were used as coagulants at varying doses and varying colour removal efficiency was measured. For the Fenton process, COD and colour removal efficiencies were found to be 78% and 95% for the Fenton process, and to be 64% and 71% for the Fenton-like process (Fe³⁺/H₂O₂), respectively. Ozonation experiments were conducted at different initial pH values and fixed ozone doses. Ozonation resulted in 43% COD and 97% colour removal whereas these rates increased to 54% and 99% when 5 mg/l hydrogen peroxide was added to the wastewater before ozonation at the same dose. The operating costs of all proposed treatment systems were also evaluated in this study.     

Synthesis and characterization of composite flocculant PAFS–CPAM for the treatment of textile dye wastewater

In this study, a new composite flocculant was prepared by premixing polymeric aluminum ferric sulfate (PAFS) with cationic polyacrylamide (CPAM) to treat textile dye wastewater. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were conducted to investigate the structure and morphology of the PAFS–CPAM. The effects of flocculant dosage, initial pH of textile dye wastewater, and settling time after flocculation on the removal of turbidity and chemical oxygen demand (COD) were examined. The flocculation efficiency of PAFS–CPAM for dye treatment was compared with PAFS, CPAM, PAFS/CPAM (PAFS followed by CPAM), and CPAM/PAFS (CPAM followed by PAFS). The synergy of PAFS and CPAM increased the (Fe–Al)_b species of PAFS–CPAM. Treatment with PAFS–CPAM was more effective in removing turbidity and COD than PAFS, CPAM, PAFS/CPAM, and CPAM/PAFS. The turbidity and COD removal rates of textile wastewater were higher than 80 and 90% in the pH range of 5.5 to 8.5, respectively. Furthermore, PAFS–CPAM demonstrated excellent performance in reducing sludge volume after flocculation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40062.     

Physico-chemical treatment of indigo dye wastewater

In the present study, colour removal and chemical oxygen demand removal from indigo dye wastewater have been evaluated using various coagulants/flocculants. Laboratory-scale experiments were conducted using chemical coagulants–flocculants on synthetic as well as actual indigo dye wastewater and under ambient liquid temperature. Up to 99% colour removal was observed during treatment of synthetic indigo dye effluent with FeSO₄, alum, polyelectrolyte and lime. Colour removal efficiencies of up to 97%, 97% and 95% were observed when denim plant wastewater (equalisation tank) was treated with alum, lime and FeSO₄ at dosages of 2, 2.5 and 2.5 g/l, respectively. Up to 95%, 94% and 87% colour removal efficiencies were observed when denim plant (dyebath) wastewater was treated with alum, lime and FeSO₄ at dosages of 225, 1000 and 225 mg/l, respectively.     

The optimization of the photo-oxidation parameters to remediate wastewater from the textile dyeing industry in a continuous stirred tank reactor

The remediation of textile dying wastewater was carried out at ambient temperatures in a pilot-scale continuous stirred tank reactor by using the photo-Fenton oxidation process. The preliminary results suggest that the treatment system reached a steady state condition within 5–10 min after it was started up. By using a 2 ^k factorial design, the effects of various parameters on the removal efficiency of color, BOD and COD were identified under steady state conditions. The removal efficiencies of color and BOD were affected by the feed rate of H₂O₂ and Fe²⁺, whereas none of the parameters in the investigated ranges affected the removal efficiency of COD. Consequently, using univariate analysis to investigate higher parameter range values, the optimum conditions for treating textile wastewater were found to be 25 ml H₂O₂/min, 5 ml Fe²⁺/min and 90 W UV-A power for 20 min. In addition, the removal of all pollutants was enhanced within the acidic pH range. Approximately 69.2, 99.4 and 48.5% of color, BOD and COD were removed, respectively. However, the concentration of TDS increased slightly during the treatment period due to the formation of new species or intermediate oxidation products. Nevertheless, all values of pollutants in the treated wastewater except COD were in the range of the standard values permitted for discharge into the environment.     

Using electrocoagulation-electroflotation technology to treat synthetic solution and textile wastewater, two case studies

The purpose of this study was to investigate the effects of the operating parameters, such as pH, initial concentration (C_i), duration of treatment (t), current density (j), interelectrode distance (d) and conductivity (κ) on the treatment of a synthetic wastewater in the batch electrocoagulation (EC)-electroflotation (EF) process. The optimal operating conditions were determined and applied to a textile wastewater. Initially a batch-type EC-EF reactor was operated at various current densities ranging from 11.55 to 91.5 mA/cm² and various electrode gaps (1, 2 and 3 cm). For solutions with 300 mg/L of silica gel, good turbidity removal (89.6%) was obtained without any coagulant when the current density was 11.55 mA/cm², and with initial pH at 7.6, conductivity at 2.1 mS/cm: the treatment time was hold for 10 min and the electrode gap was 1 cm. Application of the optimal operating parameters on a textile wastewater showed a high removal efficiency for the following variables: suspended solid (SS) 85.5%, turbidity 76.2%, biological oxygen demand (BOD₅) 88.9%, chemical oxygen demand (COD) 79.7%, and color over 93%.     

Spent green tea leaves for decolourisation of raw textile industry wastewater

True colour measurements of wastewater samples, in terms of American Dye Manufacturers' Institute values, were used to evaluate the effectiveness of decolourisation of textile wastewater using spent green tea leaf powder waste. Raw wastewater samples with a true colour of 868 ADMI were used in the batch adsorption experiments. Results revealed that the true colour removal efficiency of the raw textile wastewater was high in acidic solution and at high temperature, indicating an endothermic nature of the system. The major functional groups of the green tea leaf powder waste involved in adsorption were identified by Fourier Transform‐infrared spectroscopy analysis. Adsorption kinetic data were modelled using the modified Freundlich and intraparticle diffusion kinetics equations. Fitting results of the Langmuir adsorption isotherm showed that the adsorption capacity of the green tea leaf powder waste was 775 ADMI g^?1, which is higher than that of powder activated carbon (526 ADMI g^?1). The low activation energy values (13.9 kJ mol^?1) suggested that adsorption was governed by a diffusion process and the reaction involved a physisorption mechanism. From the perspectives of waste utilisation, remarkable colour adsorption capacity and inexpensive and abundant availability, green tea leaf waste is an attractive alternative for decolourisaton of textile wastewater. Because high temperature favours colour removal, green tea leaf powder can be directly applied in raw textile wastewater treatment.     

Evaluation of the Efficiency of a Combined Adsorption–Ultrafiltration System for the Removal of Heavy Metals,Color, and Organic Matter from Textile Wastewater

In this work an ultrafiltration (UF) membrane system was investigated for the treatment of textile wastewater. UF membranes were assisted by activated sludge and minerals, which were employed as sorbents, to remove Cu(II), Pb(II), Zn(II), Ni(II), color, and organics. Significant variations were observed in metal removal efficiencies among the textile wastewater samples of different origin, even at the same pH (= 6) due to the presence of different compounds in wastewater. At the examined pH range (5.63–9.21), the dominant mechanism for copper and lead removal was the formation of insoluble metals due to precipitation and complexation of metal ions with wastewater compounds, including adsorption of metals on suspended solids and colloidal matter. The adsorption process of metals on minerals and activated sludge was the dominant process for nickel and zinc removal at low pH, while precipitation/complexation prevailed at higher pH. The examined adsorption-UF system could produce a treated effluent having low metal concentrations that could be safely discharged into municipal sewers. COD removal ranged from 76%–92% for the five textile wastewater samples. The color removal accomplished was significant (45%–70%), and depended on the type of dye.     

自动反冲活性炭净水器处理饮用水的实验研究

粒状活性炭净水器是净化饮用水的经济实用的深度净化设备,自动反冲洗活性炭净水器在使用寿命和运行操作上均优于传统活性炭净水器。本文对自动反冲洗活性炭净水器处理上海某区的自来水进行实验,考察了自动反冲洗活性炭净水器在不同处理水量时对污染物的去除效率,实验发现：该净水器对CODMn、色度、浊度及余氯均有较好的处理效果;自动反冲洗装置可延长活性炭使用寿命,活性炭依靠过滤截留和吸附的共同作用去除水中的浊度,利用现场快速检测余氯浓度,可间接判断活性炭是否失效。     

Advanced oxidation of raw and biotreated textile industry wastewater with O3, H2O2 /UV‐C and their sequential application

The advanced chemical oxidation of raw and biologically pretreated textile wastewater by (1) ozonation, (2) H₂O₂ /UV − C oxidation and (3) sequential application of ozonation followed by H₂O₂ /UV − C oxidation was investigated at the natural pH values (8 and 11) of the textile effluents for 1 h. Analysis of the reduction in the pollution load was followed by total environmental parameters such as TOC, COD, UV–VIS absorption kinetics and the biodegradability factor, f_B. The successive treatment combination, where a preliminary ozonation step was carried out prior to H₂O₂ /UV − C oxidation without changing the total treatment time, enhanced the COD and TOC removal efficiency of the H₂O₂ /UV − C oxidation by a factor of 13 and 4, respectively, for the raw wastewater. In the case of biotreated textile effluent, a preliminary ozonation step increased COD removal of the H₂O₂ /UV − C treatment system from 15% to 62%, and TOC removal from 0% to 34%. However, the sequential process did not appear to be more effective than applying a single ozonation step in terms of TOC abatement rates. Enhancement of the biodegradability factor (f_B) was more pronounced for the biologically pretreated wastewater with an almost two‐fold increase for the optimized Advanced Oxidation Technologies (AOTs). For H₂O₂ /UV − C oxidation of raw textile wastewater, apparent zero order COD removal rate constants (k_app), and the second order OH· formation rates (r_i) have been calculated. © 2001 Society of Chemical Industry     

Treatment of textile dyeing wastewater by electrocoagulation using Fe and Al electrodes: optimisation of operating parameters using central composite design

Textile dyeing wastewater was treated by electrocoagulation using aluminium and iron plate electrodes. Response surface methodology and central composite design were applied in the experiments and in statistical data analysis. A current density of 30–100 A m^?2, an initial pH of 4–8, and an operating time of 10–40 min were chosen as independent variables, and the chemical oxygen demand, total organic carbon, and turbidity removal efficiencies and the operating cost were selected as responses in the electrocoagulation process. The developed quadratic models for the responses and the experimental data were in good agreement with model predictions statistically (R² ≥ 0.92, Adj R² ≥ 0.82, and Prob > F < 0.004). The optimised operating variables (initial pH, current density, and operating time) and the maximum total organic carbon, chemical oxygen demand, and turbidity removal efficiencies for textile dyeing wastewater were 5.5, 63.2 A m^?2, 30.4 min, 77%, 82%, and 94% for the iron electrode and 5.6, 52.5 A m^?2, 33.9 min, 68%, 69% and 99% for the aluminium electrode respectively. Minimum operating costs for the iron and aluminium electrodes under optimum conditions were €2.1 m^?3 (€1.0 kg^?1 COD) and €2.4 m^?3 (€1.6 kg^?1 COD). The iron electrode was found to be superior to the aluminium electrode in terms of removal efficiencies and operating cost for the treatment of textile dyeing wastewater.     

Electrochemical oxidation of reactive dyes: method validation and application

Electrochemical oxidation is a very effective technique for wastewater processing and, in the textile industry, it can be employed to remove colour from residual dyeing and washing liquors. In previous studies, the main factors were established for the control of the electrochemical removal of reactive dyes from textile wastewater. Mathematical models were proposed for the decolorisation of these dyes and for the electrical consumption. In the present work, these models are analysed and a three-step methodology is established in order to determine whether a dye can be removed from wastewater by electrochemical treatment. This methodology is applied and verified on a further four reactive dyes. The mathematical models are also employed to evaluate the colour removal from textile wastewater samples containing reactive dyes.     

Experimental study on electrocoagulation of textile wastewater by continuous horizontal flow through aluminum baffles

We investigated the feasibility of applying a continuous textile wastewater (TWW) treatment, which was accomplished by using electrocoagulation (EC) unit with zigzag horizontal flow across a series of mono-polar aluminum plate baffles. The effects of operating parameters such as current density (20-80 A/m²) and detention time (5-40 min) on turbidity, color, chemical oxygen demand (COD), total suspended solids (TSS) and total dissolved solids (TDS) removal were studied. The optimum conditions were determined as 60 A/m² and 20min by monitoring zeta potential (ζ) of effluent. At the optimum conditions, removal efficiencies for turbidity (97.63%), color (87.87%), COD (93.3%), TSS (94.02%), and TDS (52.13%) were observed. Further, addition of 4mg/L of NaCl dose in the TWW modified conductivity suitably, thereby reducing electrical energy consumption per cubic meter of waste water and specific electrical energy consumption (SEEC) from 13.33 to 2.67kWh/m³, and 23.84 to 4.77kWh/kg Al, respectively. Comparing the EC with conventional coagulation process, EC showed better pollutant removal efficiency.     

Effect of coagulant types on textile wastewater reclamation in a combined coagulation/ultrafiltration system

A combination of coagulation and ultrafiltration (UF) processes for textile wastewater reclamation was investigated using various types of coagulating chemicals such as polyamine, alum, polyaluminum chloride (PACl), and ferric salts. The potential of the combined system was evaluated to replace the existing treatment processes which are composed of a flotation tank (primary step) and a series of filtration beds including sands, granular carbons, and diatomaceous powders. Regardless of the type and dosage of the coagulants, the UF system achieved substantial colloidal particle removal (>97% of turbidity was removed), but membrane fouling was mitigated in a different manner. The degree of fouling reduction was highly dependent upon the type of coagulants used, even though the turbidity and organics removal efficiencies were nearly the same. The polymeric coagulant aggravated membrane fouling, whereas the inorganic coagulants always helped reduce fouling. A residue of the coagulating polymer, which was added in the primary step and its concentration in the effluent was at an immeasurable level, was found to cause serious membrane fouling. The use of polymeric coagulants should be prevented or minimized if UF is considered for textile wastewater reclamation. Polymerized aluminum was found to be the most effective among the coagulants tested, although ferric salt was better than alum in controlling fouling. In particular, it seemed that the characteristics of coagulation chemistry and the coagulated particles had a great impact upon membrane fouling.     

Sonophotocatalytic treatment of methyl orange dye and real textile effluent using synthesised nano‐zinc oxide

In this work, experiments were carried out by combining the sonication technique with the photocatalytic technique (ultraviolet light source) for the degradation of methyl orange dye and real textile effluent. Studies were performed with variation in parameters such as oxidant (sodium persulfate), commercially available zinc oxide, methyl orange concentration, and sonochemically synthesised zinc oxide. Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and X‐ray diffraction analysis of synthesised zinc oxide showed that the particle size was in the nano range. Near‐complete colour removal by sonophotocatalytic treatment was observed for a concentration of 10 mg l^?1 of methyl orange with 1 g l^?1 of synthesised zinc oxide and 1500 mg l^?1 of sodium persulfate. For 100 mg l^?1 of methyl orange, the colour removal was 77% for 1 g l^?1 commercially available zinc oxide and 84% for 1 g l^?1 synthesised zinc oxide respectively, with 1500 mg l^?1 sodium persulfate. Similar experimental conditions were applied for the sonophotocatalytic treatment of real textile effluent with different dilutions (1:100, 1:10, and 1:1) and raw effluent. For real textile effluent, sonophotocatalytic treatment was found to be highly effective both in colour and chemical oxygen demand removal. The chemical oxygen demand removal was 88, 65, 63, and 41% for 1:100, 1:10, and 1:1 dilutions and raw effluent respectively.     

絮凝-O/A/O-絮凝工艺处理印染废水

印染废水由于色度高、水质变化大、生化性差等特点,是当前工业废水处理的难点和焦点之一。采用絮凝-O/A/O-絮凝工艺处理印染废水,经过一年的实际运行,结果如下:其中CODCr、色度、SS、氨氮的平均去除率分别为97.1%、87.5%、95.2%、87.2%以上,出水达到《纺织染整工业水污染排放标准》(GB4287-92)的一级标准。该工艺具有运行稳定、耐冲击负荷能力强、难降解的有机物去除效果好,在印染废水处理中具有明显优势。     

聚合氯化铝对印染废水的混凝效果研究

采用烧杯搅拌实验,研究了聚合氯化铝（PAC）混凝剂处理3种模拟染料废水样品的最佳投加量和最佳pH值。实验结果表明,投药浓度为2g／L（以铝计）时,且分散棕黄水样、酸性深蓝水样、混合染料水样的pH分别为9、7及6时,PAC的最佳投药量分别为18、14及21mL,除浊效果良好,其浊度去除率可达98．0％、95．7％及93．3％,色度去除率可达55．6％、73．1％及55．1％。