Xiujuan Chen

Date of Graduation

2017

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Industrial and Managements Systems Engineering

Committee Chair

Xingbo Liu

Committee Co-Chair

Konstantinos A Sierros

Committee Member

Jason P Trembly

Abstract

This study has investigated the removal of zinc ions from the synthetic wastewater models by electrocoagulation (EC) with aluminum for both cathode and anode. The results showed that EC process had a great removal when it comes to zinc contaminated water. The effects of parameters on the EC performance have been systematically investigated, such as solution conductivity, electrode spacing, initial pH, current density and initial zinc concentration. Since the wastewater in real situations usually contains several types of metals, a series of mixed cases were also studied in this work.;The results indicated that current density is critical to EC performance, in terms of the removal efficiency and energy consumption. The basic conductivity of the solution is required to decrease the EC voltage. It was demonstrated that the neutral pH is favorable for zinc removal by EC process, while the effect of electrode spacing on EC performance was not significant in this case. With a relatively low energy consumption of 0.35 kWh/m3, more than 99.5% of zinc ions were removed from the synthetic wastewater (zinc concentration 50 mg/L) within 20 min. Later with an energy consumption of 0.88 kWh/m3, highly similar removal efficiency has been achieved at zinc concentration of 250 mg/L at EC time of 50 minutes.;The kinetic study for zinc removal was performed to describe the adsorption system during EC process. The results show that the removal of zinc ions by EC process follows the first-order model with current-dependent parameters. Additionally, the removal of zinc ions fitted well with the first order model at related low initial concentration, and fitted well with the pseudo-first order model at high initial concentrations. Different mechanisms of zinc removal were implied by comparing the results of the low initial concentration (≤ 250 mg/L) and the high one (≥ 500 mg/L). It was reasonable to conclude that, beside the co-precipitation effect of the aluminum hydroxides coagulants, the reduction of zinc ions at the cathode also contributed to the zinc removal, especially at a high initial concentration. The different removal pathways of metal ions usually exist at high initial concentrations of metal ions and alkaline pH medium.

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