A Comprehensive Review of the Current Progress of Chromium Removal Methods from Aqueous Solution.

Chromium (Cr) exists in aqueous solution as trivalent (Cr 3+ ) and hexavalent (Cr 6+ ) forms. Cr 3+ is an essential trace element while Cr 6+ is a dangerous and carcinogenic element, which is of great concern globally due to its extensive applications in various industrial processes such as textiles, manufacturing of inks, dyes, paints, and pigments, electroplating, stainless steel, leather, tanning, and wood preservation, among others. Cr 3+ in wastewater can be transformed into Cr 6+ when it enters the environment. Therefore, research on Cr remediation from water has attracted much attention recently. A number of methods such as adsorption, electrochemical treatment, physico-chemical methods, biological removal, and membrane filtration have been devised for efficient Cr removal from water. This review comprehensively demonstrated the Cr removal technologies in the literature to date. The advantages and disadvantages of Cr removal methods were also described. Future research directions are suggested and provide the application of adsorbents for Cr removal from waters.