Electrocoagulation for removal of phosphate from aqueous solution: Statistical modeling and techno-economic study

The focus of this study is to evaluate electrocoagulation as a process for the remediation of phosphate contaminated synthetic aqueous solutions using scrap aluminium plate electrodes in monopolar-parallel mode. An attempt was made in modeling the phosphate removal as a function of the significant parameters as well as to optimize the process statistically with the help of Response Surface Methodology using Design Expert software Version 7.0.0. The full factorial central composite design was followed to obtain the required number of runs for batch study. Five parameters namely initial pH, inter-electrode distance (IED), the concentration of the supporting electrolyte (SEC), electrolysis-time and voltage were considered for the experimentations. A valid model to predict the removal efficiency was established and the removal efficiencies witnessed were as high as 98%. The techno-economic optimization yielded the following set of parameters as the most economical solution: pH = 7, Voltage = 11.23 V, IED = 3 cm, t = 14.03 min and SEC = 0.46 g/L exhibiting a 90% removal efficiency and an operating cost of 0.22 $/m³ of water treated or 2.52 $/Kg of phosphate removed. The study of crystallinity of the electrocoagulation byproduct was also conducted using XRD analysis, which showed the presence of amorphous or poorly crystalline phases.