Abstract:
Contamination of surface and groundwater water reservoirs with arsenic (As)
oxyanions has raised global concerns for humans as well as ecosystem. Therefore,
there is an urgent need to improve existing treatment systems with the capability of
decreasing concentration of toxic As species to a safe level. In this regard, the
optimization of process parameters of conventional C/F/S treatment systems may
provide feasible solutions to ensure public health safety. Herein, the removal response
of As oxyanions were investigated using ferric chloride (FC) in context of single,
binary, and ternary systems. Moreover, response surface methodology (RSM) and
Fourier transform infrared spectroscopic (FTIR) analysis was conducted to identify
the optimum process conditions. The results of single system with varying pH
conditions indicated that the ideal pH range for the removal of As(III, V) using FC
was (8-9) and (5-6), respectively. Furthermore, binary system showed higher removal
on As(III, V) in case of humic acid when compared with phosphate ions during
chemical coagulation process, probably because of the existence of more reactive
functional groups. The RSM study indicated that the solution containing higher
concentration of phosphate and humic acid needs a higher concentration of FC to
achieve higher As(III, V) removal in ternary environment. The As removal response
model was successfully developed and validated in the presence of humic acid and
phosphate. Moreover, RSM was found useful in determining optimum As removal
conditions by FC coagulation. In binary and ternary systems, the FTIR analysis
revealed the combined impact of reduction, complexation, and charge neutralization
as dominant As removal mechanism from complex water environment. Overall, the
current study's findings will be useful in providing new insights on the removal,
mobility, and fate of toxic As oxyanions in multicomponent environment.
