Development of an integrated electro-coagulation–flotation for semiconductor wastewater treatment

Abstract

In this study, an electro-coagulation-flotation process was used as a polishing treatment of semiconductor wastewater after precipitation. Batch mode experiments were undertaken using aluminium sheets as anode and stainless steel as cathode. Experiments on a synthetic solution showed that coupling electro-coagulation with electro-flotation in the same cell is efficient for simultaneous defluoridation and clarification. This combination was carried out by proper electrode arrangement and material choice. The performance is ascribed to the combined effect of anodically created coagulants and hydrogen micro-bubbles evolving on the cathode. The effects of the main parameters: electrode nature and arrangement, treatment time, current intensity, initial pH, initial concentration, type and concentration of supporting electrolytes were studied. Defluoridation efficiency may reach 90% corresponding to residual fluoride of 4.61 mg/L, while, turbidity removal efficiency may reach about 85% which corresponds to a residual turbidity of 3.09 NTU. The obtained final concentrations comply with national hazardous waste regulations.

Simultaneous removal of chromium(VI) and fluoride by electrocoagulation–electroflotation: Application of a hybrid Fe-Al anode

“…Determined amounts of K 2 Cr 2 O 7 are added to the solution. After mixing at 400 rpm of 1 min, the pH was adjusted and stirring at 200 rpm takes place for 30 min [31]. Solutions are immediately introduced in the EC reactor for polishing treatment.…”

“…These anions originate from neutralization of corresponding acids used in wafer etching process [9,13,31]. In order to assess their effect, four types of salts (NaCl, NaNO 3 , Na 2 SO 4 and NaH 2 PO 4 ) were examined.…”

“…31 species The (Cr, Fe)(OH) 3 was inferred as product of co-precipitation of Cr(III) and Fe(III) [42,56].…”

“…However, attack by medium alkalinity results in additional dissolution of Al/Fe cathode [29] which gives rise of electrode consumption. Thus, the use of an inert cathodic material like stainless steel would be a better choice [30,31].…”

Treatment of Fez City (Morocco) Effluent by Chemical Coagulation (CC) and Electrocoagulation (EC)

“…This study aims at clarifying sewage of the most polluted area, recognized by many craft activity in the region of Fes (AinNokbi ,Old Medina), by conducting a comparative test of treatment by two techniques: The chemical coagulation(CC) and ectrocoagulation (EC) using aluminum plates . Which have proven their effectiveness on several types of effluents [6,7,8].…”