Optimization of oxide coating process on quartz sand for arsenic (III) removal from groundwater

This paper presents optimization of various oxide coating processes on quartz sand surface. The chemical characteristics of quartz sand collected from the Yamuna river, Allahabad, India, shows 82.022% SiO₂ besides other oxides. The optimal coating temperature was 60°C; optimal pH_coating≈0.5; optimal heating time was 60 hours and percentage iron salt [Fe(NO₃)₃·9H₂O] was 8–10% w/w for iron oxide coated sand (IOCS) with maximum As(III) removal efficiency. The 60 h heating time in iron oxide coating process yields maximum Fe (mg/g) on the sand surface. The pH_coating has shown considerable effect on arsenic removal efficiency during optimization of sulfate modified iron oxide coated sand (SMIOCS) media. The SMIOCS prepared at pH_coating<1.0 was quite efficient compared to media prepared at pH_coating≅neutral and pH_coating≅12.05. The mixed oxide coated sand (MOCS) prepared at pH_coating<1.0 has shown better arsenic removal efficiency in comparison to other mixed oxide coated sand media. The BET surface area varied between 2.55 and 7.895 m²/g for particle size ranging from 0.324 mm to 0.716 mm for different coated sand media. The pH_zpc values indicate that the IOCS and SMIOCS media are positively charged at neutral pH, whereas uncoated sand is negatively charged. Equilibrium and column studies results show that IIS and MIOCS media have better As(III) removal potential compared with other media.