Factors affecting iron and manganese dissolution in groundwater: treatments with simultaneous oxidation and precipitation methods.

Abstract

This study explores variations in groundwater (GW) pH, conductivity, ammonium, iron, and manganese parameters to reveal prospective interactions having an impact on the dissolved metal concentrations. To this end, bivariate and partial correlation procedures were applied to the data to obtain incisive evaluation. Besides characterisation efforts, photocatalytic iron and manganese removal experiments were also carried out with Ni-doped TiO₂ nano-composite thin films (TFs) on real GW samples. UV-A (365 nm) An LED array was used as the illumination source. The experimental setup was based on three treatment routes including photocatalytic oxidation (PCO), NaOH-aided precipitation and PCO with simultaneous precipitation (SPCO-P). The main statistical analysis and treatment efforts have been performed on data and samples of a single well, respectively (N = 15). However, extended statistical analysis has also been performed on larger data groups (N = 1366) obtained from different GW sources as well. Analytical results have revealed that about 90% of iron and manganese were in oxidised forms which do not precipitate by simple pH regulation. Statistical analysis has also revealed significant interactions between metal concentrations and observed parameters depending on the level of pH and conductivity. Furthermore, the SPCO-P strategy has provided a four-fold increase in reaction rate (pseudo-first-order, k_obs: 0.04 min^-1). Removal efficiencies of iron and manganese also increased from 10% to 96% - 85%, respectively.