Coagulation and flocculation behavior of fines in foid-bearing rock processing plant (FRPP) wastewater at alkaline environment

Abstract

In this study, the effects of two different coagulants with different valence counter-ions; iron (II) sulphate; (FeSO4) and iron (III) chloride (FeCl3), and high molecular weight (HMW) flocculants with three different ionic charges (anionic, cationic and nonionic) on turbidity removal from wastewater of foid-bearing rock processing plant were investigated depending concentration and time (0–60 min) at alkaline pH values (pH 8–12). In addition, the effects of binary coagulant/flocculant and flocculant/flocculant mixtures on turbidity removal were also investigated depending on the time (0–60 min) using previously determined coagulant/flocculant concentrations at natural pH value (pH 8.0 ± 0.1) of the plant wastewater. According to the results, the turbidity removal efficiencies varied depending on pH and time; the highest turbidity removal (≤97%) was obtained with 160 mg/L of FeCl3 at pH 12 while the highest turbidity removal (≤99%) in flocculation processes were obtained with 1.50 mg/L of non-ionic flocculant at the same pH. In the analyses with binary coagulant/flocculant and flocculant/flocculant mixtures at pH 8; the turbidity removal efficiency of ≤99% was obtained with the binary mixtures of 80 mg/L FeCl3 and 0.50 mg/L non-ionic flocculant, and the turbidity removal efficiency of ≤98% was obtained with the binary mixtures of 0.50 mg/L no-ionic flocculant and 0.50 mg/L cationic flocculant.