Preparation of a phenylboronic acid and aldehyde bi-functional group modified silica absorbent and applications in removing Cr(vi) and reducing to Cr(iii)

Abstract

Cr(VI) is a great threat to the ecological environment and human health, so it is urgent to remove Cr(VI) from the environment. In this study, a novel silica gel adsorbent SiO₂–CHO–APBA containing phenylboronic acids and aldehyde groups was prepared, evaluated and applied for removing Cr(VI) from water and soil samples. The adsorption conditions including pH, adsorbent dosage, initial concentration of Cr(VI), temperature and time were optimized. Its ability in removing Cr(VI) was investigated and compared with three other common adsorbents, SiO₂–NH₂, SiO₂–SH and SiO₂–EDTA. Data showed SiO₂–CHO–APBA had the highest adsorption capacity of 58.14 mg g⁻¹ at pH 2 and could reach adsorption equilibrium in about 3 h. When 50 mg SiO₂–CHO–APBA was added in 20 mL of 50 mg L⁻¹ Cr(VI) solution, more than 97% of Cr(VI) was removed. A mechanism study revealed that a cooperative interaction of both the aldehyde and boronic acid groups is attributed to Cr(VI) removal. The reducing function was gradually weakened with the consumption of the aldehyde group, which was oxidized to a carboxyl group by Cr(VI). This SiO₂–CHO–APBA adsorbent was successfully used for the removal of Cr(VI) from soil samples with satisfactory results which indicates a good potential in agriculture and other fields.