Sequential application of aerated electrocoagulation and γ-Fe2O3 nanoparticle adsorption for COD removal: Consuming the least amount of energy and economic evaluation

Abstract

Although promising, in many applications electrocoagulation (EC) is not adequate for decreasing pollutants to permissible levels for discharge. In this study, treatment of industrial wastewater from a textile dyeing plant was investigated by a combined process of aerated EC, followed by the use of γ-Fe2O3 (Maghemite) nanoparticle adsorbents. The properties of the synthesized nanoparticles were determined by XRD, SEM and FTIR analyses. The effect of aeration rate (0–2.65 L/min), nanoparticle concentration (0–480 mg/L) and initial pHEC (3–7), were investigated on COD removal of the sequential process and a quadratic model (p-value 0.98) was developed. Then, under two scenarios, optimization was performed. In the first scenario, the highest COD removal was targeted irrespective of energy or chemical use. Under the second scenario, energy and chemical use were considered as well as the reduction of capital and operating expenditures. The comparison of the two scenarios led to aeration rates of 1.5 L/min vs. 0.86 L/min, nanoparticle concentration of 160 mg/L vs. 120 mg/L, and pHEC of 4 vs. 5.32. The COD removal in the first scenario was 88.7% whereas it was reduced to 67.7% when CAPEX and OPEX were considered. An economic evaluation was performed to investigate the commercial application of the system, showing promising results. According to this evaluation operating costs were reduced from 13.01$/ m3 (scenario 1) to 9.78 $/ m3 (scenario 2) that is in competitive range compared with other commonly proposed processes such as AOP. According to the obtained results, the combined method of aerated electrocoagulation and maghemite nanoparticle adsorption has a good performance in removing COD from textile wastewater.

Keywords

• Electrochemistry
• Gamma Fe2O3 nanoparticles
• Energy consumption
• Sludge volume ratio
• Optimization