Experimental and DFT theoretical study for understanding the adsorption mechanism of toxic dye onto innovative material Fb-HAp based on fishbone powder

Abstract

The massive production of liquid discharges from the textile industry represents a global challenge based primarily on maintaining the equilibrium between ecological safety and commercial gain. In this regard, the physicochemical treatment of fishbone powder leads to hydroxyapatite (Fb-HAp) which is an innovative nanocomposite with effective morphology and specific surface area for the removal of the toxic dye Brilliant Green (BG) in an aqueous solution. The maximum adsorption capacity of BG on the Fb-HAp adsorbent’s surface is 49.1 mg g−1. The kinetics and isotherm of BG dye adsorption on Fb-HAp are best represented by the pseudo-second order’s equation and Langmuir's model, while the thermodynamic parameters show that the reaction is physical, feasible, spontaneous, and endothermic. The adsorption of BG on Fb-HAp experimental values were consistent with the values predicted by the response surface methodology and lead to a maximum removal rate of 99.87% under the conditions of pH 12, adsorbent dose 1 g L−1, and dye’s concentration 10 mg L−1. Quantum chemical calculations were executed using density functional theory (DFT) calculations at B3LYP 6-31G (d,p) to correlate their electronic properties with the experimental results. Based on the high electrophilicity values, low electronegativity, and Monte Carlo results, it is found that the basic form of the BG dye has a large overlap with the Fb-HAp adsorbent compared to the acid form. The low cost of the Fb-HAp material ($1.384 per gram) and its regeneration cycles show that it is environmentally friendly and very effective for dye removal in the textile industry.