Decolourization of melanoidins by a electrocoagulation process using aluminium electrodes

Abstract

The decolourization of melanoidins was studied with a batch electrocoagulation (EC) process using aluminium electrodes. The effects of conductivity (kappa = 500-3000 mu S/cm), initial pH(i) (4.2-8.2), current density (j = 2.5-7.5A/m(2)), initial melanoidin concentration (C-0 = 100-800 mg/L) and operating time (t(EC) = 0-60 min) were investigated on the decolourization efficiency. The results obtained from the EC process were extremely efficient and able to achieve a decolourization efficiency of >98% at pH(i) = 4.2, j = 5A/m(2), kappa = 2500 mu S/cm, C-0 = 100 mg/L and t(EC) = 10 min. The decolourization performance was dependent on pH(i) value since the lower pH values led to faster reactions and higher decolourization efficiency. Melanoidins in the EC process were removed by precipitation and charge neutralization at pH <6.5, and both adsorption and sweep coagulation by amorphous Al(OH)(3(s)) occurred at pH > 6.5. The operating cost was calculated as 0.0096 (sic)/m(3).