Application of low-cost adsorbents for dye removal – A review

As the environment preservation gradually becomes a matter of major social concern and more strict legislation is being imposed on effluent discharge, more effective processes are required to deal with non-readily biodegradable and toxic pollutants. Synthetic organic dyes in industrial effluents cannot be destroyed in conventional wastewater treatment and consequently, an urgent challenge is the development of new environmentally benign technologies able to mineralize completely these non-biodegradable compounds. This review aims to increase the knowledge on the electrochemical methods used at lab and pilot plant scale to decontaminate synthetic and real effluents containing dyes, considering the period from 2009 to 2013, as an update of our previous review up to 2008. Fundamentals and main applications of electrochemical advanced oxidation processes and the other electrochemical approaches are described. Typical methods such as electrocoagulation, electrochemical reduction, electrochemical oxidation and indirect electro-oxidation with active chlorine species are discussed. Recent advances on electrocatalysis related to the nature of anode material to generate strong heterogeneous OH as mediated oxidant of dyes in electrochemical oxidation are extensively examined. The fast destruction of dyestuffs mediated with electrogenerated active chlorine is analyzed. Electro-Fenton and photo-assisted electrochemical methods like photoelectrocatalysis and photoelectro-Fenton, which destroy dyes by heterogeneous OH and/or homogeneous OH produced in the solution bulk, are described. Current advantages of the exposition of effluents to sunlight in the emerging photo-assisted procedures of solar photoelectrocatalysis and solar photoelectro-Fenton are detailed. The characteristics of novel combined methods involving photocatalysis, adsorption, nanofiltration, microwaves and ultrasounds among others and the use of microbial fuel cells are finally discussed.

Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods. An updated review

A review on biodiesel production using catalyzed transesterification

Recent developments of zinc oxide based photocatalyst in water treatment technology: A review

A review on chemical coagulation/flocculation technologies for removal of colour from textile wastewaters.

Treatment of textile wastewaters by electrocoagulation using iron and aluminum electrodes.

The photocatalytic decolorization of aqueous solutions of Remazol Red RR, a commercial azo-reactive textile dye, in the presence of various semiconductor powder suspensions has been investigated in a quartz batch reactor with the use of artificial light sources (UV-C). ZnO and TiO2 have been found the most active photocatalysts; however ZnO indicated slightly higher efficiency. The effects of various process variables on decolorization performance of the process have been investigated. The results showed that the decolorization efficiency increases with increase in pH, attaining maximum value at pH 10 for ZnO. The zero-point charge for ZnO is 9.0 above which ZnO surface is negatively charged by adsorbed OH− ions, favoring the formation of strong oxidant OH radicals. The efficiency is inversely related to the dye concentration; increasing dye concentration enhances dye adsorption on the active sites of the catalyst surface, and consequently hinders OH− adsorption on the same sites, this results with a decreasing OH formation rate.

Photocatalytic decolorization of Remazol Red RR in aqueous ZnO suspensions

Operating cost analysis of electrocoagulation of textile dye wastewater

Treatment of the textile wastewater by combined electrocoagulation.

The removal of pollutants from effluents by electrocoagulation has become an attractive method in recent years. This paper deals with the batch removal of the reactive textile dye Remazol Red RB 133 from an aqueous medium by the electrocoagulation method using aluminum electrodes. The effects of wastewater conductivity, initial pH, current density, stirring rate, dye concentration, and treatment time on the decolorization efficiency and energy consumption have been investigated. Aluminum hydroxypolymeric species formed during an earlier stage of the operation efficiently remove dye molecules by precipitation, and in a subsequent stage, Al(OH)3 flocs trap colloidal precipitates and make solid−liquid separation easier during the flotation stage. These stages of electrocoagulation must be optimized to design an economically feasible electrocoagulation process.

Mahmut Bayramoglu

Papers

Treatment of textile wastewaters by electrocoagulation using iron and aluminum electrodes.

Photocatalytic decolorization of Remazol Red RR in aqueous ZnO suspensions

Operating cost analysis of electrocoagulation of textile dye wastewater

Treatment of the textile wastewater by combined electrocoagulation.

Decolorization of Reactive Dye Solutions by Electrocoagulation Using Aluminum Electrodes