Electro-coagulation coupled electro-flotation process: Feasible choice in doxycycline removal from pharmaceutical effluents

Abstract

Electrochemical treatment involving a coupled coagulation and floatation was performed in the removal of doxycycline hyclate (DCH) from aqueous solutions. All the experiments were carried out in an electrochemical reactor of 1.5 L which contained aluminum electrodes as cathode and anode. The removal of doxycycline hyclate (DCH) species by EC/EF was determined as a function of electrolysis time, pH, current intensity, flow rate and DCH concentration. From the observed results, it was corroborated that the DCH removal through the EC/EF process was excellent. The effective contribution from initial pH (7.03) and current intensity (5.39 mA cm−2) was very much remarkable and well apparent from flocs of good buoyancy. The removal of DCH was inversely proportional to spacing between electrodes (SBE) and circulating flow rate in the presence of the supporting NaCl electrolyte of 1 g L−1. It was also highly promoted by the addition of NaCl in comparison with NaNO3 and KCl to the electrolytic system. The compliance of four kinetic models was verified with DCH removal system. The free energy values from DKR model suggested the nature of bonding by chemical forces. Characterization by FTIR, SEM and XRD interpreted the assignments of various functional groups, surface morphology and crystalline incorporated amorphous nature, respectively of electro-generated flocs. The current efficiency and specific electrical energy consumption at optimized conditions of the EC/EF system were calculated. Keywords: Electro-coagulation–flotation, Aluminum electrodes, Doxycycline hyclate