Electrocoagulation induced treatment of indigo carmine textile dye in an aqueous medium: the effect of process variables on efficiency evaluated using biochemical response of Gammarus pulex

Indigo carmine removal from aqueous solutions was investigated by the electrocoagulation process and biochemical responses of Gammarus pulex to solutions before and after treatment were studied. Electrocoagulation experiments in the first stage were carried out with central composite design (CCD) using response surface methodology (RSM). Optimization of process variables that maximize indigo carmine removal by electrocoagulation process was carried out by using a second-order model within the studied test range of various process variables. According to the optimization results, optimum conditions for obtaining 82.55% maximum indigo carmine removal were pH 5.86, a current density of 13.31 mA/cm², an indigo carmine concentration of 20.01 mg/L, and a time period of 115.80 min. Under optimum conditions for indigo carmine removal, the amount of sludge formed was 0.928 kg/m³, electrode consumption was 0.0305 kg/m³, and energy consumption was 7.461 kWh/m³. The operating cost was calculated as 0.79 US$/m³ under treatment conditions where optimum indigo carmine removal was achieved. In the second stage, G. pulex was exposed to treated and untreated synthetic indigo carmine solutions obtained from experiments according to optimum conditions in order to investigate the biochemical response for 24 and 96 h. Treatment efficiency was evaluated with superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and cytochrome P450 1A1 (CYP1A1) biomarkers. Results clearly showed that the electrocoagulation process was a simple and effective treatment method for the decolorization of wastewaters containing indigo carmine dye. The bioassays used in the present study provided good credibility for checking the detoxification of treated and untreated indigo carmine solutions.

Adsorptive removal of methylene blue (MB) and malachite green (MG) dyes from aqueous solutions using graphene oxide (GO)

Graphene oxide (GO) synthesized via modified Hummers method was studied for adsorption of methylene blue (MB) and malachite green (MG) dyes from aqueous solutions. It is hypothesized that electrostatic interactions between dye molecules and surface of GO will facilitate charge carrier movements and degrade the dye in an efficient way. The as synthesized GO was characterized using various characterization techniques such as XRD, Raman, FTIR, UV–Vis, SEM and EDAX. The experimental results suggest that dye removal percentage will increase with increase in adsorbent dosage, time as well as solution pH and the process was exothermic in nature. The adsorption data at 293 K could be fitted by Langmuir equation with a maximum adsorption amount of 119.04, 102.4 mg/g and Langmuir adsorption equilibrium constant of 1.58, 0.867 L/mg for MB and MG dyes, respectively. The outcomes of present article will help not only to understand the adsorption characteristics of GO on MB and MG dyes but also paves path towards development of highly oxidized GO surface for degradation of complex dyes.

Decolorization of Reactive Black B from wastewater by electro-coagulation: optimization using multivariate RSM and ANN

The present study is aimed to model and optimize the electrocoagulation (EC) process with five important parameters for the decolorization of Reactive Black B (RBB) from simulated wastewater. A multivariate approach, response surface methodology (RSM) together with central composite design (CCD) is used to optimize process parameters such as pH (5–9), electrode gap (0.5–2.5 cm), current density (2.08–10.41 mA/cm2), process time (10–30 min), and initial dye concentration (100–500 mg/l). The predicted percentage decolorization of dye is obtained as 97.21% at optimized conditions: pH (6.8), gapping (1.3 cm), current density (8.32 mA/cm2), time (23 min), and initial dye concentration (200 mg/L), which is very close to experimental percent decolorization (98.41%). The statistical analysis of variance (ANOVA) is performed to evaluate the quadratic model (RSM), and shows good fit of experimental data with coefficient of determination R2 >0.93. An Artificial Neural Network (ANN) is also used to predict the percentage decolorization and gives overall 94.96% which shows performance accuracy between the predicted and actual value of decolorization. The additional considerations of operating cost and current efficiency are also taken care to show the efficacy of EC process with mathematical tool. The sludge characteristics are determined by FE-SEM/EDX.

Synthesis of nickel nanoparticles using Citrullus colocynthis stem extract for remediation of Reactive Yellow 160 dye

In current years, pollution caused by synthetic dyes has become one of the most serious environmental issues. By rapidly developing industrial units, effluents having synthetic dyes are directly or indirectly being discharged into the environment. Bio-sorption is cost-effective way for the eradication of toxic dyes present in textile effluent. The present study involves the synthesis of nickel nanoparticles using Citrullus colocynthis stem extract. The characterization of synthesized nickel nanoparticles (Ni-NPs) was done by SEM. The synthesized Ni-NPs were used to degrade the Reactive Yellow 160 dye following the optimization of different experimental parameters. The maximum decolorization (91.4%) was obtained at 0.02% dye conc., 9 mg/L conc. of Ni-NPs, pH 7 at 40 °C. TOC and COD were used to assess the efficiency of this experiment. Percent reduction in COD and TOC was found to be 84.35% and 83.24% respectively. The degradation pathway of dye under study confirmed the formation of non-toxic end-products.