Electrocoagulation studies on removal of cadmium using magnesium electrode

Abstract

The removal of cadmium from aqueous solution was carried out by electrocoagulation using magnesium as anode and stainless steel as cathode. Various operating parameters on the removal efficiency of cadmium were investigated, such as initial cadmium ion concentration, initial pH, current density and temperature. The optimum removal efficiency of 98.6% was achieved at a current density of 0.2 A dm -2 at a pH of 7.0. The experimental data were tested against different adsorption isotherm models for describing the electrocoagulation process. The adsorption of cadmium preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules. First and second-order rate equations were applied to study adsorption kinetics. The adsorption process follows second order kinetics model with good correlation. Temperature studies showed that adsorption was endothermic and spontaneous in nature.

Removal of lead from aqueous solutions by electrocoagulation: isotherm, kinetics and thermodynamic studies

“…The 1,476.6/cm peak indicates the bent vibration of H-O-H. Absorption band at 3,696.4/cm implies the transformation from free protons into a proton conductive state in brucite. The strong peak at 439.2/cm is assigned to the Mg-O stretching vibration (Golder et al 2006;Vasudevan et al 2010). The spectrum data are in good agreement with the reported data (Golder et al 2006).…”

“…Positive values of entropy change show the increased randomness of the solution interface during the adsorption of lead on the adsorbent (Table 4). The enhancement of adsorption capacity of magnesium hydroxide at higher temperatures may be attributed to the enlargement of pore size and/or activation of the adsorbent surface (Vasudevan et al 2010). Using Lagergren rate equation, second-order rate constants and correlation coefficient were calculated for different temperatures (303-333 K).…”

“…In this process, anodic dissolution of metal electrode takes place with the evolution of hydrogen gas at the cathode (Vasudevan et al 2010). Electrochemically generated metallic ions from the anode can undergo hydrolysis to produce a series of activated intermediates that are able to destabilize the finely dispersed particles present in the water to be treated.…”

Treatment of Cr, Ni and Zn from galvanic rinsing wastewater by electrocoagulation process using iron electrodes

“…The EC process does not require any supplementary addition of chemicals, reduces the volume of produced sludge and is cost-effective as compared to the conventional methods. Recently, the EC process was employed for the removal of metals, such as Cu, Cr and Ni, from a metal plating wastewater with Fe-Fe and Fe-Al plate electrode pairs [10]; Ni, Cu and Cr from a galvanic wastewater with Fe and Al electrodes [12]; Ni and Cd from an electroplating rinse water with Fe electrode [13]; Cu, Pb and Cd from a synthetic wastewater with Fe plate electrode [14]; Cu from a copper polishing wastewater with Al-Fe electrodes [15]; Mn from a synthetic wastewater with Al plate electrode [16]; Hg from a synthetic wastewater with Fe and Al plate electrodes [17]; Ni and Zn from a metal plating wastewater using steel electrodes [18], and other similar studies [19][20][21][22][23][24][25][26][27]. Table 1 also provides an overview of EC studies performed in the literature with real and synthetic wastewaters containing heavy metals.…”

Analysis of the Adsorption Behaviour of Cadmium on Aluminium-Pillared Diatomite in a Solid/Liquid System Using Classical Adsorption Theory

“…A large amount of wastewater is discharged into surface water owing to the rapid development of various industries such as mining, metal plating, metallurgy and fertilizer production (Singh et al 2003;Wang et al 2006;Srivastava and Majumder 2008;Aksoy et al 2011;Sarkar et al 2011). These kinds of wastewaters have to be treated in order to remove toxic metals, such as cadmium, lead, copper, zinc, mercury, chromium and nickel, before being discharged into the environment.…”