Efficient Removal of Methyl Red Dye by Using Bark of Hopbush

Abstract

Highlights: Analysis of low-cost, bio-adsorbent bark of the D. viscosa plant, proved to be an efficient ad-sorbent for the removal of methyl red dye from aqueous solution. The pseudo-second-order kinetic model and Freundlich adsorption isotherm appeared to be the best fit for describing the adsorption of methyl red onto D. viscosa plant bark. D. viscosa plant bark as an adsorbent showed good adsorption capability in tap water and river water. Methyl red (MR) dye, one of the azo dyes, is mutagenic and its persistence has negative effects on the environment and people’s health. The current work is the first to demonstrate that methyl red dye can be removed effectively and sustainably, utilizing biomass derived from the bark of the Dodonaea viscosa (Hopbush) plant. The Hopbush bark shows effective adsorption of MR, upto 73%, under optimized conditions in an aqueous medium. The experimental conditions were optimized by examining the effect of time, initial dye concentration, pH and ionic strength on the adsorption process in an aqueous medium. Maximum (i.e., 73%) adsorption of MR removal (500 ppm) was observed in highly acidic conditions (pH = 1) at a contact time of 75 min. The pseudo-second-order kinetic model and Freundlich adsorption isotherm appeared to be the most appropriate for characterizing the MR’s adsorption onto the bark of the D. viscosa plant. Furthermore, it was shown that bark powder outperformed animal charcoal, silica gel, and powdered flowers, as well as the leaves of the same species, in terms of adsorption capacity. Thus, a natural adsorbent that is inexpensive and readily available—the bark of the D. viscosa plant—can be used to effectively remove harmful dyes from contaminated water and protect water resources from harmful pollutants.