Multi-functional Biochar Novel Surface Chemistry for Efficient Capture of Anionic Congo Red Dye: Behavior and Mechanism

Abstract

Anionic ionizable synthetic dyes can exert specific toxicity in human health as well as disorder aquatic life. Plus it is quite difficult to remove them by applying conventional adsorbents having negative surface charges. To resolve this crucial issue, the multi-functionalized biochar having novel surface chemistry was tested to make it more efficient for Congo red (CR) anionic dye elimination from an aqueous solution even under severe acidic conditions as well as in the presence of unwanted co-present constituents. The prepared amino grafted biochar (AMBC) showed maximum monolayer adsorption capacity of 89.3 mg g−1 at 20 °C due to the presence of both –COOH and –NH2 protonated groups. In order to support the successful involvement of both grafted dominantly available amino group and the fraction of residual –COOH group present on AMBC surface for CR dye uptake, the TEM and XPS analysis were employed. On behalf of the adsorption kinetics, isotherms and thermodynamics studies as well as XPS results, it was deduced that CR anionic dye adsorption onto AMBC was exothermic and spontaneous, and the anticipated CR dye removal mechanism was referred to chemisorption such as electrostatic interactions. Desorption experiments were conducted to ensure the feasibility of the exhausted AMBC adsorbent regeneration and its reusability potential. These research findings provide an environmentally friendly adsorbent having versatile applications and inexpensive adsorbent for potential elimination of anionic ionizable CR dye from aqueous solution.