Sulfide-enhanced carboxymethyl cellulose stabilised nano zero-valent iron for chromium(VI) mitigation in water: Evidence from batch and column studies

The primary source of chromium pollution in water is industrial operations such as electroplating, leather tanning, and textile manufacture, which use chromium for its ability to resist corrosion. Hexavalent chromium (Cr(VI)), the most detrimental variant, presents significant health hazards, such as cancer. It is crucial to effectively manage and decrease chromium levels to protect human and environmental health, especially in industrial regions where its presence in water is a persistent issue. This work examined the removal of Cr(VI) by sulfidated carboxymethyl cellulose stabilised nano zerovalent iron (S-CMC-nZVI). S-CMC-nZVI exhibited outstanding uniformity and corrosion resistance. Batch experiments revealed that several factors influenced the degree to which S-CMC-nZVI particles eradicated Cr(VI). The parameters to be considered included pH, initial Cr(VI) concentration, coexisting ions, and S/Fe molar ratio. When the sulfur to iron molar ratio was increased from 0 to 0.4, Cr(VI) removal efficiency increased from 73.89 % to 99 %. A pseudo-second-order kinetic model described Cr(VI) removal, and the Langmuir isotherm model determined the highest adsorptive capacity (311.02 mg/g). The presence of bicarbonate and nitrate anions have minimal inhibitory effects on removal of Cr(VI). Experiments on polluted groundwater showed that synthesised nanoparticles may remove Cr(VI) over a long time. Column investigations showed that increasing S-CMC-NZVI concentration increased Cr(VI) removal. The Adsorption, reduction and coprecipitation were major processes responsible for Cr(VI) removal. The research demonstrates that S-CMC-nZVI is a promising material for the in-situ remediation of Cr(VI)-contaminated groundwater.