Reductive decolorization of a textile reactive dyebath under methanogenic conditions

The objective of the present study was to assess the biological decolorization of an industrial, spent reactive dyebath and its three dye components (Reactive Blue 19 [RB 19], Reactive Blue 21 [RB 21], and Reactive Red 198 [RR 198]) under methanogenic conditions. Using a mixed, methanogenic culture, batch assays were performed to evaluate the rate and exten of color removal as well as any potential toxic effects. Overall, a high rate and extent of color removal (>10 mg/[L·h] and 88%, respectively) were observed in cultures amended with either RB19 (an anthraquinone dye) or spent dyebath at an initial dye concentration of 300 mg/L (expressed as RB 19 equivalent) and 30 g/L of NaCl. Inhibition of acidogenesis and, to a larger degree, of methanogenesis resulting in accumulation of volatile fatty acids was observed in both RB 19- and spent dyebath-amended cultures. RB 21 (a phthalocyanine dye) and RR 198 (an azo dye) tested at an initial concentration of 300 mg/L did not result in any significant inhibition of the mixed methanogenic culture. Based on results obtained with cultures amended with RB 19 with and without NaCl, as well as a control culture amended with 30 g/L of NaCl, salt was less inhibitory than either RB 19 or the dyebath. Therefore, the toxic effect of the spent dyebath is at least partially attributed to its major dye component RB 19 and NaCl. Further testing of the effect of RB 19 decolorization products on the methanogenic activity in the absence of NaCl demonstrated that these products are much less inhibitory than the parent dye. Although color removal occurred despite the severe culture inhibition, biological decolorization of full-strength reactive spent dyebaths using methanogenic cultures in a repetitive, closed-loop system is not deemed feasible. For this reason, a fermentative and halotolerant culture was developed and successfully used in our laboratory for the decolorization of industrial reactive dyebaths with 100 g/L of NaCl.     

Biosorption of Basic Green 4 from aqueous solution by Ananas comosus (pineapple) leaf powder

Biosorption characteristics of Ananas comosus (pineapple) leaf powder was investigated for decolorization of Basic Green 4 (BG 4), a cationic dye from its aqueous solutions employing a batch experimental set-up. Parameters that influence the sorption process such as pH, biosorbent dosage, contact time, initial dye concentration and temperature were systematically studied. The optimum conditions for removal of BG 4 were found to be pH 9.0, contact time=150 min, biosorbent dosage=5.0 g L(-1), initial dye concentration=50 mg L(-1). The temperature had a strong influence on the biosorption process. Further, the biosorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Brunauer, Emmett, Teller (BET) surface area and pore size analysis. Experimental biosorption data were modeled by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The biosorption process followed the Langmuir isotherm model with high coefficients of correlation (R(2)>0.99) at different temperatures. The pseudo second order kinetic model fitted well in correlation to the experimental results. Activation energy of the biosorption process (E(a)) was found to be 45.79 kJ mol(-1) by using the Arrhenius equation, indicating chemisorption nature of BG 4 sorption onto pineapple leaf powder. Thermodynamic parameters suggest that the biosorption process is spontaneous and exothermic in nature. Overall, the present findings suggest that this environmentally friendly, efficient and low-cost biosorbent may be useful for the removal of BG 4 from aqueous media.     

Optimization of the oxalate catalyzed photoelectro-Fenton process under visible light for removal of Reactive Red 195 using a carbon paper cathode

The decolorization of Reactive Red 195 (RR195) by the oxalate catalyzed photoelectro-Fenton (PEF) process using carbon paper electrode as a cathode under visible light was studied. Comparison between electro-Fenton (EF), PEF, and PEF/oxalate processes for the removal of RR195 showed that color removal follows in decreasing order: PEF/oxalate > PEF > EF. Response surface methodology (RSM) was used to determine the effects of the four main independent parameters (initial dye, oxalate and Fe³⁺ concentrations, and reaction time) on decolorization efficiency. A high coefficient of determination value (R ² = 0.963) has resulted from the analysis of variance (ANOVA). The optimum values of the initial Fe³⁺ concentration, the initial amount of oxalate, the initial dye concentration, and the reaction time were found to be 0.3 mM, 0.6 mM, 20 mg/L, and 120 min, respectively. A high decolorization efficiency (>93 %) was experimentally obtained for RR195 under the established optimum conditions. The response surface plots were employed to establish the effect of experimental parameters on the decolorization efficiency. These results clearly indicated the success of RSM as a suitable method for optimizing the operating conditions. The mineralization of the dye was investigated by total organic carbon (TOC) measurement. 96.2 % mineralization of 50 mg/L RR195 was observed at 9 h.     

Adsorption of Acid Dyes from Aqueous Solutions by Calcined Alunite and Granular Activated Carbon

Dyestuff production units and dyeing units have always had a pressing need for techniques that allow economical pretreatment for color in the effluent. The effectiveness of adsorption for dye removal from wastewaters had made it an ideal alternative to other expensive treatment options. This paper deals with an investigation on alunite, existing wide reserves in Türkiye and in the world, for dye removal. Calcined alunite was utilized for this study and its performance evaluated against that of granular activated carbon (GAC). The use of calcined alunite for the removal of Acid Blue 40 and Acid Yellow 17 (AB 40 and AY 17) from aqueous solution at different calcination temperature and time, particle size, pH, agitation time and dye concentration has been investigated. The adsorption followed by Langmuir and Freundlich isotherms. The process follows first order adsorption rate expression and the rate constant was found to be 7.65 × 10^–2 and 5.74 × 10^–2 min^–1 for adsorption of AB 40 and AY 17 on calcined alunite, and 8.41 × 10^–2 and 10.04 × 10^–2 min^–1 for adsorption of AB 40 and AY 17 on GAC, respectively. The equilibrium saturation adsorption capacities were 212.8 mg dye/g calcined alunite and 151.5 mg dye/g calcined alunite for AB 40 and AY 17, respectively. The adsorption capacities were found to be 57.47 mg and 133.3 mg dye per g of GAC for AB 40 and AY 17, respectively. The results indicate that, for the removal of acid dye, calcined alunite was most effective adsorbent, although comparable dye removals were exhibited by GAC.     

Biosorption of Acid Blue 25 by unmodified and CPC-modified biomass of Penicillium YW01: kinetic study, equilibrium isotherm and FTIR analysis

The main objective of this work was to investigate the biosorption performance of unmodified and Cetylpyridinium chloride (CPC)-modified biomass of Penicillium YW 01 for Acid Blue 25 (AB 25). Maximum biosorption capacity of AB 25 onto CPC-modified biosorbent was 118.48 mg g(-1) under phosphoric-phosphate buffer with initial dye concentration of 200 mg L(-1) at 30°C. The biosorption pattern of AB 25 onto unmodified biosorbent in aqueous solution and phosphoric-phosphate buffer was well fitted with both Langmuir and Freundlich isotherm models. While the equilibrium data of CPC-modified biosorbent in aqueous solution and phosphoric-phosphate buffer failed to fit the Freundlich isotherm model, indicating the monolayer biosorption formed onto CPC-modified biosorbent. The values of initial biosorption rate of biosorbent in phosphoric-phosphate buffer were found to be higher than that of corresponding values in aqueous solution, indicating phosphoric-phosphate buffer enhanced the initial biosorption rate of biosorption process. Weber-Morris model analysis indicated that the boundary layer effect had more influence on the biosorption process in phosphoric-phosphate buffer. The BET surface area of CPC-modified biosorbent (0.5761 m(2) g(-1)) was larger than that of unmodified biomass (0.3081 m(2) g(-1)). Possible dye-biosorbent interactions were confirmed by Fourier transform infrared spectroscopy.     

Fabrication of PANI@Fe–Mn–Zr hybrid material and assessments in sono-assisted adsorption of methyl red dye: Uptake performance and response surface optimization

In recent decades, industrial wastewater discharge containing toxic or hazardous manufactured dyes has risen tremendously, creating a serious environmental threat. A new hybrid adsorbent, [email protected]–Mn–Zr synthesized by mixing Fe–Mn–Zr metal oxide composite with polyaniline (PANI), was used to study methyl red (MR) dye removal from aqueous solution. The adsorption process was observed to be influenced by the sonication time, dose of [email protected]–Mn–Zr, and initial concentration of MR dye. At an initial MR dye concentration of 25 mg/L, 0.25 g/L of [email protected]–Mn–Zr dose, 15 min of sonication, and pH 7.0, the maximum MR dye adsorption efficiency of 90.34% was achieved. Kinetic analysis was performed using five different kinetic models, which shows that the pseudo-second-order kinetic model had the best fit among the five models. The Langmuir isotherm best fits the adsorption experiments at pH 7.0, yielding a significant MR dye uptake capacity of 434.78 mgg^?1. The most significant adsorption mechanisms that have been observed in uptake of MR dye onto [email protected]–Mn–Zr were electrostatic attraction, π-π bond interactions and hydrogen bonding. Response surface optimization study was performed for optimizing the experimental conditions from which maximum dye removal of 98.19% was obtained at contact time of 12 min, initial MR dye concentration of 15 mg/L and [email protected]–Mn–Zr dose of 0.4 g/L. Use of real wastewater and water samples suggest that there is only 6–19% reduction in the dye removal efficiency as compared to the blank or controlled experiments conducted with deionized water.     

Modeling the mechanism involved during the sorption of methylene blue onto fly ash

Batch sorption experiments were carried out to remove methylene blue from its aqueous solutions using fly ash as an adsorbent. Operating variables studied were initial dye concentration, fly ash mass, pH, and contact time. Maximum color removal was observed at a basic pH of 8. Equilibrium data were represented well by a Langmuir isotherm equation with a monolayer sorption capacity of 5.718 mg/g. Sorption data were fitted to both Lagergren first-order and pseudo-second-order kinetic models and the data were found to follow pseudo-second-order kinetics. Rate constants at different initial concentrations were estimated. The process mechanism was found to be complex, consisting of both surface adsorption and pore diffusion. The effective diffusion parameter D(i) values were estimated at different initial concentrations and the average value was determined to be 2.063 x 10(-9)cm2/s. Analysis of sorption data using a Boyd plot confirms the particle diffusion as the rate-limiting step for the dye concentration ranges studied in the present investigation (20 to 60 mg/L).     

Adsorption of Hazardous Azorhodanine Dye from an Aqueous Solution Using Rice Straw Fly Ash

The potential of using rice straw fly ash (RSFA) as low-cost adsorbents for the removal of hazardous azorhodanine (AR) dye from aqueous solution was investigated. The effects of different variables in the batch method as a function of solution pH, contact time, concentration of adsorbate, adsorbent dosage, and temperature were investigated, and optimal experimental conditions were ascertained: 0.05 g for initial dye concentration of 20–100 mg/L at pH 2. The experimental equilibrium data were tested by the isotherm models, namely the Langmuir and Freundlich adsorption and the isotherm constants were determined. The kinetic models, pseudo-first-order and pseudo-second-order, were employed to analyze the kinetic data. The activation energy of adsorption was also evaluated and found to be +10.89 kJ.mol^?1, indicating that the adsorption is physisorption. Various thermodynamic parameters, such as Gibbs free energy, entropy, and enthalpy of the ongoing adsorption process, have been calculated and found to be spontaneous and exothermic, respectively.     

镁铝二元水滑石的焙烧产物对染料废水酸性红88的吸附

研究了镁铝水滑石的焙烧产物(LDO)对阴离子染料废水酸性红88(AR88)的吸附特征。分别考察了染料的初始浓度、吸附剂投加量、初始pH值、反应温度和竞争离子等因素的影响,并用XRD、红外光谱对水滑石以及吸附前后的LDO进行了表征。实验结果表明：LDO对高浓度的AR88具有良好的去除效果,在15 ℃、pH=10～11下,1.0 g·L^-1的LDO对浓度为2 000 mg·L^-1的AR88的去除率可高达99.95%,吸附容量为1 999.0 mg·g^-1。经4次回收重复利用的LDO对AR88的去除率仍为90%以上。     

Green synthesis and application of nanoscale zero-valent iron/rectorite composite material for P-chlorophenol degradation via heterogeneous Fenton reaction

A zero-valent iron/rectorite nanocomposite (NZVI/rectorite) was developed as a heterogeneous H₂O₂ catalyst for P-chlorophenol degradation. The physicochemical properties of NZVI/rectorite were characterized by various techniques including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive spectrometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller analysis. Results showed that NZVI sphere nanoparticles were successfully loaded on the rectorite surface with less aggregation and good dispersion. Moreover, compared with acid-leached rectorite (30.91 m²/g), the NZVI/rectorite appeared to have larger surface area (50.75 m²/g). In addition, the effects of pH, reaction time, initial P-chlorophenol concentration, catalyst amount, and H₂O₂ dosage on the P-chlorophenol degradation were systematically investigated. Results showed that NZVI/rectorite presents better properties for the degradation and mineralization of P-chlorophenol compared with pristine NZVI due to the large surface area, low aggregation, and good dispersion of the former. The degradation mechanisms of P-chlorophenol by NZVI/rectorite were adsorption and reduction coupled with a Fenton-like reaction. Four successive runs of the stability and regeneration study also showed that the NZVI/rectorite were unchanged even after 100% of P-chlorophenol degradation ratio. This study has extended the application of NZVI/rectorite as environment function material for the removal of P-chlorophenol from the environment.     

木质素阳离子絮凝剂的合成及其絮凝性能研究

以酶解木质素、甲醛、二甲胺及阳离子化试剂为原料,制备了木质素基阳离子絮凝剂.改变阳离子化试剂的用量、缩合反应的温度和时间等因素,制备不同阳离子度的木质素阳离子絮凝剂;通过其对酸性黑10B的脱色效果研究,确定了最优的制备方案.利用最优条件制备的木质素阳离子絮凝剂对三种不同种类阴离子染料废水进行了絮凝脱色处理.结果表明,原...     

Removal of Pararosaniline Hydrochloride Dye (Basic Red 9) from Aqueous Solution by Electrocoagulation: Experimental,Kinetics, and Modeling

In this work, the removal of pararosaniline hydrochloride (Basic red 9) dye from aqueous solutions by electrocoagulation was investigated. The effect of parameters such as current density, initial pH, electrolysis time, inter-electrode distance, initial dye concentration and salt concentration on dye removal efficiency were investigated. The experimental results showed that 99% dye removal was observed after 30 minutes of electrolysis for an initial dye concentration of 100 mg/L, current density of 111.1 A/m² and initial pH of 7.0. It was observed that an increase in current density, time of operation and decrease in inter-electrode distance improved the dye removal efficiency. The optimum pH range for highest dye removal was 5.0–10.25. It was also observed that increase in salt concentration in the solution reduces the specific electrical energy consumption. The kinetic study inferred that the dye removal primarily follows a first order reaction. Finally, phenomenological models were proposed to illustrate the dependence of dye removal rate constant and specific electrical energy consumption on current density, inter-electrode distance, initial dye concentration and salt concentration.     

Study of flocculation with PONILIT GT-2 anionic polyelectrolyte applied into a chemical wastewater treatment

This paper discusses the applications of synthetic PONILIT GT-2 anionic polyelectrolyte in conjuction with ferric sulfate in a chemical wastewater treatment viz. wastewater from ceramics manufacturing. Synthetic wastewaters with different colloid concentrations were prepared and the coagulation-flocculation process followed by sedimentation and/or filtration was studied. Variables associated with the chemical wastewater composition, mixing time, and the coagulant and flocculant dose are considered in order to appreciate the process efficiency in terms of turbidity, chemical oxygen demand (COD), and color removal. The degrees are higher for turbidity and color (> 80 %) removal respectively, and, satisfactory for COD (< 50 %). An empirical model was elaborated by a third order rotatable design 2³ type, considering ferric sulfate dose, polyelectrolyte dose, and mixing time as independent variables, while the turbidity and color removal efficiencies were chosen as optimization criteria. The empirical model was found adequate for the chemical wastewater treatment. Also, an analysis of the model was performed to find the optimal operating conditions, in order to apply this process for an efficient chemical wastewater treatment using ferric sulfate as coagulation agent and PONILIT GT-2 anionic polyelectrolyte as flocculation agent. The optimal values correspond to a ferric ions concentration of 6.093 mg/L, a polyelectrolyte dose of 0.651 mg/L, and a mixing time of 24.024 minutes for turbidity removal (95.869 %), respectively, and, to a ferric ions concentration of 6.01 mg/L, a polyelectrolyte dose of 0.69 mg/L, and a mixing time of 26 minutes for color removal (98.741 %).      

Dye Pollutants removal from Waste water using Metal Oxide Nanoparticle embedded Activated Carbon: An Immobilization study

This study evaluated the feasibility of Rhodamine-B dye (Rh B) removal from aqueous solution, using Lead-Iron Oxide nanoparticles Loaded Activated Carbon (FePbO@AC). The parameters like pH, contact time, adsorbent/adsorbate dosage and temperature on adsorption was studied. Optimized conditions are pH of 7.0, 25?min contact time, 50?ppm of dye concentration and 200?mg of adsorbent concentration. The kinetics of adsorption was calculated using pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The calculations revealed that the pseudo-second-order kinetic equation best-fit the adsorption data. The Langmuir isotherm model best fit the equilibrium data. The maximum sorption capacity (Q_max) for dye is 1000?mg Rh B/g FePbO@AC. Change in entropy (ΔS), Gibb’s free energy change (ΔG), and enthalpy (ΔH) were calculated for the adsorption of Rh B dye.     

Cellulose nanocrystals as promising adsorbents for the removal of cationic dyes

Cellulose nanocrystals (CNCs) prepared from cellulose fibre via sulfuric acid hydrolysis was used as an adsorbent for the removal of methylene blue (MB) from aqueous solution. The effects of pH, adsorbent dosage, temperature, ionic strength, initial dye concentration were studied to optimize the conditions for the maximum adsorption of dye. Adsorption equilibrium data was fitted to both Langmuir and Freundlich isotherm models, where the Langmuir model better described the adsorption process. The maximum adsorption capacity was 118 mg dye/g CNC at 25 °C and pH 9. Calculated thermodynamic parameters, such as free energy change (ΔG = ?20.8 kJ/mol), enthalpy change (ΔH = ?3.45 kJ/mol), and entropy change (ΔS = 0.58 kJ/mol K) indicates that MB adsorption on CNCs is a spontaneous exothermic process. Tunability of the adsorption capacity by surface modification of CNCs was shown by oxidizing the primary hydroxyl groups on the CNC surface with TEMPO reagent and the adsorption capacity was increased from 118 to 769 mg dye/g CNC.     

On-line monitoring of opaque liquids by photoacoustic spectroscopy

A new photoacoustic sensor system for on-line monitoring of highly concentrated and optical opaque liquid samples is presented. The dyeing of textiles is performed with highly concentrated dye solutions with concentrations ranging from 50 mg L(-1) up to 40 g L(-1). For process optimization and control of the wastewater, an on-line monitoring of the dye concentration is needed. Optical transmission measurements allow the determination of the dye concentration in a relatively small range. Samples with concentrations in the upper mg L(-1) and g L(-1) range have to be diluted before the measurement due to their optical opacity. Additionally, light-scattering particles have a strong effect on the transmitted light intensity. By photoacoustic spectroscopy, concentrations in condensed matter can be determined over several orders of magnitude. Furthermore, scattering particles do not generate any photoacoustic signal.     

Adsorption of Acid Blue 193 from aqueous solutions onto Na-bentonite and DTMA-bentonite

Dodecyltrimethylammonium bromide-modified bentonite (DTMA-bentonite) was prepared and tested as an adsorbent for an acid dye (Acid Blue 193, AB193) removal from aqueous solution in comparison with Na-bentonite. The effect of various experimental parameters was investigated using a batch adsorption technique. In this manner, the adsorption isotherms, adsorption kinetics, and temperature and pH effects upon Acid Blue 193 adsorption on Na-bentonite and DTMA-bentonite were thoroughly examined. Results show that a pH value of 1.5 is favorable for the adsorption of Acid Blue 193. The isothermal data could be well described by the Freundlich equation. The dynamical data fit well with the pseudo-second-order kinetic model. The adsorption capacity of DTMA-bentonite (740.5 mg g(-1)) was found to be around 11 times higher than that of Na-bentonite (67.1 mg g(-1)) at 20 degrees C. Thermodynamic parameters such as activation energy (E(a)) and change in the free energy (DeltaG(0)), the enthalpy (DeltaH(0)), and the entropy (DeltaS(0)) were also evaluated. The overall adsorption process was exothermic but it is only spontaneous at 20 degrees C. The results indicate that Na-bentonite and DTMA-bentonite could be employed as low-cost alternatives to activated carbon in wastewater treatment for the removal of color which comes from textile dyes.     

Enhanced adsorption performance of a novel Fe‐Mn‐Zr metal oxide nanocomposite adsorbent for anionic dyes from binary dye mix: Response surface optimization and neural network modeling

A novel adsorbent, Fe‐Mn‐Zr metal oxide nanocomposite was synthesized and investigated for removal of methyl orange (MO) and eosin yellow (EY) dyes from binary dye solution. The magnetic nanocomposite has shown surface area of 143.01 m²/g and saturation magnetization of 15.29 emu/g. Optimization was carried out via response surface methodology (RSM) for optimizing process variables, and optimum dye removal of 99.26% and 99.55% were obtained for MO and EY dye, respectively with contact time 62 min, adsorbent dose 0.45 g/l, initial MO concentration 11.0 mg/l, and initial EY concentration 25.0 mg/l. A feed forward back propagation neural network model has shown better prediction ability than RSM model for predicting MO and EY dye removal (%). Adsorption process strictly follows Langmuir isotherm model, and enhanced adsorption capacities of 196.07 and 175.43 mg/g were observed for MO and EY dye, respectively due to synergistic effects of physicochemical properties of trimetal oxides. Surface adsorption and pore diffusions are the mechanisms involved in the adsorption as revealed from kinetic studies.     

聚合氯化铝的制备及在微污染水处理中的应用

用酸溶法制备聚合氯化铝,对合成产品进行红外光谱分析,并应用于微污染原水的处理。处理微污染原水结果表明:当投加量为40.0 mg/L,pH值为6.0～9.0时,剩余浊度达到1.0NTU以下,总有机碳(Total Or-ganic Carbon,TOC)去除率达到41.2%。对比试验结果表明自制的聚合氯化铝的除浊效果优于一些常见工业聚合氯化铝。     

超声协同TiO_2光催化脱除燃料油中有机硫的研究

采用溶胶凝胶法制备纳米TiO2光催化剂,引入超声作用,以空气中的氧气为氧化剂,正辛烷为模拟油品对燃料油中硫化物的脱除进行了研究。考察了光照强度、催化剂用量、反应时间、二苯并噻吩(DBT)初始浓度、超声功率等因素对TiO2光催化二苯并噻吩溶液降解效率的影响。结果表明,引入超声后DBT的降解率提高了10%左右,并在TiO2用量为2 g/L,通气量为800 mL/min,光照距离20 cm,DBT初始浓度为600 mg/L,反应时间为150 min,超声功率为500 W的条件下,DBT降解率达到了72.6%。