Evaluation of Zeta Potential and Particle Size Measurements of Multiple Coagulants in Semiconductor Wastewater

摘要

Chemical precipitation method utilizing calcium salts has been extensively used to treat fluoride-containing wastewater from semiconductors industries. Aim of this paper it to investigate the coagulation behavior of calcium salts (CaCl_2), aluminium salts (PACl) and polymer by using dynamic light scattering technique that is applied as an alternative methodology to pre-determine the optimum pH and dosage range. The stability and behavior of the wastewater sample and coagulants were studied in terms of zeta potential and z-average hydrodynamic diameter profiles as a function of pH (pH 2 to 12). It is observed that optimum pH range and dosage range for fluoride-containing wastewater, CaCl_2, and PACl were at pH 9, pH 5 with 3 mg/L CaCl_2, and pH 7 with 1 mg/L PACl, respectively. This condition is followed by the addition of polymer which act as a flocculant at three different pH regimes; pH below than pHPZC (pHH_(PZC)), pH at pH_(PZC) (pH=pH_(PZC)) and pH above pH_(PZC) (pH> pH_(PZC)). Experimental results indicated that addition of polymer at pH=pH_(PZC) (CaF2/PACl at pH 5) and dosage of 2 mg/L promotes the biggest size of z-average hydrodynamic diameter of the particles which is 4500±0.9 d.nm with zeta potential value of 0.2±0.1 mV. Therefore from this study proved that pH adjustment played an important roles during coagulation and flocculation process especially in aggregation or disaggregation of the particles.