Green fabrication of bentonite/chitosan@cobalt oxide composite (BE/CH@Co) of enhanced adsorption and advanced oxidation removal of Congo red dye and Cr (VI) from water.

Bentonite/chitosan composite supported by green fabricated Co3O4 was successfully synthesized and its physicochemical properties were investigated utilizing several analytic techniques. The formation of the composite was confirmed by the XRD patterns, SEM, HRTEM images, and FT-IR analysis. The adsorption properties of bentonite/chitosan@Co3O4 for acidic dye (Congo red) and Cr(VI) ions were investigated. The kinetic studies reflected the saturation of the composite surface after 480 min for both Congo red molecules and Cr(VI) ions. Additionally, the systems are of chemisorption nature and showed excellent fitting with Pseudo-second order model. The mathematical parameters of the isotherm models revealed a monolayer uptake of Congo red molecules and Cr(VI) ions and represented mainly by the Langmuir model. The theoretical calculated maximum adsorption capacity (qmax) is 303 mg/g and 250 mg/g for Congo red molecules and Cr(VI) metal ions, respectively. The composite is of high reusability and can be used effectively for six runs of decontamination of Congo red molecules and Cr(VI) ions. Moreover, it is of high oxidation properties and can be used in the photocatalytic reduction of Congo red molecules and Cr(VI) ions from water. Besides that, bentonite/chitosan@Co3O4 green composite was used in purification of realistic water samples which make it one of the promising adsorbents.