Valorization of Agricultural Wastes as Low‐Cost Adsorbents Towards Efficient Removal of Aqueous Cr(VI)

Extent of heavy metal ions in natural aqueous environment increases alarmingly owing to improper discharge of waste water from industries and mining sites. This not only deteriorates the water quality but also potentially threatens human health through the water cycle. Among various heavy metal ions, contamination of Cr(VI) has been an important cause of concern because of its carcinogenic and mutagenic effects. Biosorption is preferred over other existing technologies for remediation of aqueous Cr(VI) as it is environmentally benevolent, inexpensive, and logistically easier. Biomaterials like agricultural wastes (AWs) are found beneficial for Cr(VI) sequestration since these have advantages of no sludge generation, high metal selectivity, efficient regeneration and good recycling ability. In this chapter, adsorption behavior of AWs toward Cr(VI) has been discussed. We have overviewed the influence of adsorption parameters like pH, time, temperature, initial Cr(VI) concentration, and bio-adsorbent dose for maximum removal. Parameters of thermodynamics, kinetic models, and isotherm equations were systematically reviewed for predicting possible uptake mechanism. Finally, advantages, limitations, and perspectives of AWs toward sequestration of aqueous Cr(VI) were depicted in the conclusion.