A review of the literature published in from 2008 to 2010 on topics related to electrochemical treatment within wastewater was presented. The review included several sections such as optimization, modeling, various wastewater treatment techniques, analytical and instrumentation, and comparison with other treatment methods.

https://engagedscholarship.csuohio.edu/cgi/viewcontent.cgi?article=1108&context=encee_facpub

Electrocoagulation in Wastewater Treatment

Textile industry is one of the fastest growing industries and significantly contributes to the economic growth in Malaysia. However, this industry also has high water consumption and subsequently produces high discharge rate of wastewater with high load of contaminants. The release of dyes into the environment during textile fiber dyeing and finishing processes is a main source of water pollution. Individual wastewater treatment through physical, biological, or chemical method is often very costly and results in large amount of sludge. Thus, there is a need to look for alternative treatment processes that covers from pre to post wastewater treatment stage. This paper reviews the current scenario with respect to textile industry effluent in Malaysia and technologies available for the treatment of the effluent. Prospects, challenges, and recommendations for future direction as well as on-going research works dedicated to the treatment of textile wastewater are also reviewed in detail.

Current Status of Textile Industry Wastewater Management and Research Progress in Malaysia: A Review

Natural dyes have been used from ancient times for multiple purposes, most importantly in the field of textile dying. The increasing demand and excessive costs of natural dye extraction engendered the discovery of synthetic dyes from petrochemical compounds. Nowadays, they are dominating the textile market, with nearly 8 × 105 tons produced per year due to their wide range of color pigments and consistent coloration. Textile industries consume huge amounts of water in the dyeing processes, making it hard to treat the enormous quantities of this hazardous wastewater. Thus, they have harmful impacts when discharged in non-treated or partially treated forms in the environment (air, soil, plants and water), causing several human diseases. In the present work we focused on synthetic dyes. We started by studying their classification which depended on the nature of the manufactured fiber (cellulose, protein and synthetic fiber dyes). Then, we mentioned the characteristics of synthetic dyes, however, we focused more on their negative impacts on the ecosystem (soil, plants, water and air) and on humans. Lastly, we discussed the applied physical, chemical and biological strategies solely or in combination for textile dye wastewater treatments. Additionally, we described the newly established nanotechnology which achieves complete discharge decontamination.

https://www.mdpi.com/2076-3417/11/14/6255/pdf

Diversity of Synthetic Dyes from Textile Industries, Discharge Impacts and Treatment Methods

In this research, the efficiency of electrocoagulation treatment process using aluminum electrodes to treat synthetic wastewater containing Reactive Red198 (RR198) was studied. The effects of parameters such as voltage, time of reaction, electrode connection mode, initial dye concentration, electrolyte concentration, and inter electrode distance on dye removal efficiency were investigated. In addition, electrical energy consumption, electrode consumption, and operating cost at optimum condition have been investigated. The results showed that dye and chemical oxygen demand removals were 98.6 and 84%, respectively. Electrode consumption, energy consumption and operating cost were 0.052 kg/m 3 , 1.303 kWh/m 3 and 0.256 US$/m 3 , respectively. Dye removal kinetic followed first order kinetics. It can be concluded that electrocoagulation process by aluminum electrode is very efficient and clean process for reactive dye removal from colored wastewater.

Dye Removal, Energy Consumption and Operating Cost of Electrocoagulation of Textile Wastewater as a Clean Process

Heavy metals have frequently been detected in metal plating wastewater. In this study, electrocoagulation method using iron (Fe) and aluminum (Al) electrodes was applied to simultaneously remove four heavy metals (Cu, Ni, Zn, Cr) in artificial metal plating wastewater. The Fe electrode showed greater removal efficiency for especially Cr than did the Al electrode due to the reduction of Cr6+ ion by Fe2+ ions produced from electrode. Alkaline pH favored electrocoagulation because of the abundance of hydroxide (OH−) ions; thus, metal hydroxides can be formed readily under alkaline pH. The metal removal increased with current density, as Fe2+ ion was generated more effectively at high current. However, the electrolyte concentration did not significantly affect metal removal efficiency. In electrocoagulation experiments using Fe electrodes, the mass of sludge formed was 0.68–2.50 kg/m3 and the amount of energy consumed was 0.37–2.78 kW h/m3, respectively, during the treatment of artificial metal plating wastewater containing four heavy metals in the absence of cyanide, which increased to 3.64–4.74 kg/m3 and 4.80–5.04 kW h/m3 for artificial wastewater in the presence of cyanide. The FTIR spectra of the sludge samples generated when using Fe and Al electrodes showed that all four metals exhibited OH stretching peaks, implying that main removal mechanism of metals during electrocoagulation is the precipitation with metal hydroxide. Iron sludge was composed mainly of Fe3O4 and FeO(OH), and Al sludge was mostly AlO(OH). When using Fe electrode in the presence of cyanide, cyanide was also adsorbed onto iron sludge via Fe-CN bonding.

Removal mechanism of heavy metal (Cu, Ni, Zn, and Cr) in the presence of cyanide during electrocoagulation using Fe and Al electrodes

The electrocoagulation (EC) treatment of Acid Blue 113 (AB 113) was performed on the basis of chemical oxygen demand (COD) removal efficiency using an iron anode. The process variables, including current density (1-5 A/dm 2 ), pH (5.5-7.5), and supporting electrolyte concentration (1-3 g/L) were investigated. Under the optimum operating conditions, more than 91 % COD removal efficiency was found. The optimum conditions were obtained with 3 A/dm 2 of current density, pH 6.5, and 2 g/L of supporting electrolyte concentration. COD removal rates obtained during the EC process can be described using a pseudo-kinetic model. The experimental kinetic data fit well with pseudo first-order kinetic model, with no significant change on the rate constant after 3 A/dm 2 of current density. The absorption spectra and Fourier transform infra red analysis were also performed to characterize the mechanism and nature of dye cleavage.

Mohan Saravanan

Papers

Treatment of Acid Blue 113 Dye Solution Using Iron Electrocoagulation