Using experimental design for the screening and optimization of key factors on silica particles adsorption using magnetic nanoparticles – a case study of chemical mechanical polishing wastewater treatment

Abstract

This study applied magnetic nanoparticles (MNPs) to chemical mechanical polishing wastewater treatment using experimental design (Plackett–Burman methods) to select the key factors among pH, mixing, Polyaluminum chloride dosage, settling time, MNPs dosage, and temperature and using response surface methodology (RSM) to determine the optimal values of key factors. Research results showed that the key factors influencing processing performance were pH and rpm, and the optimal conditions were a pH of 4.9 and rpm of 68. The turbidity removal rate through RSM simulation was 90%; under this parameter, the actual turbidity removal rate in the experiment was 89%, which was extremely close to the simulation value; this value was also much higher than the nonoptimized removal rate of 61 ± 8%. Additionally, in the subsequent regeneration and reuse experiment involving mixing and ultrasound for desorption and regeneration, the number of recoveries were 4 and 5, respectively. The study showed that the average particle size of MNPs following ultrasonic vibration was reduced; the effect was optimal at 23 to 15 nm. Therefore, a removal rate of over 80% could be maintained for the fifth ultrasonic regeneration, and the energy of the mixing method may not have been sufficient, causing incomplete desorption and a turbidity removal rate of only 71%.