Scrutiny of interference effect of ions and organic matters on water treatment using supported nanoscale zero-valent iron

Nanoscale zero-valent iron (nZVI) supported on heat-modified activated charcoal (nFe(0)/AC) can improve nitrate reduction and phosphate adsorption regarding reaction conversion, adsorption capacity, and kinetics. It is more effective in terms of mobility and stability than bare nZVI. Both nZVI and its supported type were synthesized, characterized, and examined in interference studies for applications in environmental remediation technologies. Solutions of 45.18 mg nitrate-N/L, 50 mg phosphorus/L, and a mixture of them were treated using nZVI and nFe(0)/AC in municipal wastewater body and also deionized water body in the coexistence of anions (phosphate and sulfate), cations (cuprous and cupric), organic matters (humic acid), and hardness (calcium carbonates) at different concentrations. Results showed the significant impact of interference on nitrate reduction and superiority of nFe(0)/AC by ca. 27% to ca. 183% increase in treatment efficiency over nZVI. Anions were easily attracted to the surface of nano-iron particles resulting in a negative intervening effect. Hardness and contaminants of municipal wastewater provided a negative impact and significantly interfered with nitrate removal, while organic matters had a lower negative interference compared to others. On the contrary, copper cations could improve removal efficiency until complete elimination of nitrate. The experimental data were best-fitted to a kinetic rate model that combined the pseudo-first-order rate with the deactivation rate arising from the passivation of interfering substances on the surface of nZVI-based materials. The value of parameters of this rate equation could estimate the degree and type of interference occurring during nitrate decontamination.