Synthesis of polyaluminum chloride: Optimization of process parameters, characterization and performance investigation for water treatment

The present work was aimed to synthesis of polyaluminum chloride (PAC) using calcium oxide as a basification agent and optimization of process parameters on the yield of medium polymer species in PAC. The synthesis parameters were concentration of aluminum chloride hexahydrate (0.4 to 0.8 M), basicity ratio (2.0 to 2.4), reaction temperature (60 to 80 °C) and time (180 to 360 min). The performance of PΑC for water treatment was also investigated. The monomeric, medium polymeric and colloidal species of PAC were determined by Ferron test method. The PAC samples were characterized using various analytical techniques such as X-ray diffractometer (XRD), Fourier transformer infrared spectrometer (FTIR), scanning electron microscope (SEM), differential scanning calorimeter (DSC), dynamic light scattering (DLS) and electrophoretic light scattering (ELS). The turbidity and natural organic matter (NOM) of water samples were also determined using turbidimeter and UV–vis methods, respectively. The optimum yield of medium polymeric (Alb) content in PΑC species was predicted to 74.6 %, and the verification experiment result was 73.5 % at 0.5 M, 2.2, 75 °C and 273 min. The performance of PAC for water treatment revealed that the removals efficiencies of turbidity and NOM were reached to 98 % (pH = 7.2) and 86 % (pH = 6.8), respectively, at coagulant dose of 15 mg L−1 as Al. The residual aluminum concentration in the treated water was <0.2 mg L−1 which confirmed that the PAC could be used to treat drinking water.