Anthill clay activated Ocimum gratissimum extract for effective adsorption of methylene blue and chromium (VI) ion from wastewater: Insights into the adsorption isotherms, kinetics, thermodynamics, and mechanisms
Lukman Shehu Mustapha, Samuel Oluwaseun Kolade, Sodiq Olayemi Durosinmi, Inn Shi Tan, Sie Yon Lau, Kehinde Shola Obayomi
Abstract
The removal of methylene blue (MB) dye and hexavalent chromium (Cr(Vl)) ions from water bodies have necessitated the search for a promising adsorbent material with high adsorptive performance, facile operation, and economical. Here, a novel adsorbent was prepared by activating anthill clay (AC) with Ocimum gratissimum leaf extract (OG@AC) by ultrasonic strategy method to eliminate MB and Cr(Vl) from the aqueous environment; however, the activation strategy serves as an important factor that influenced the adsorptive performance towards MB and Cr(Vl). Furthermore, a high BET surface area of 120.48 m 2 /g was measured for OG@AC which is attributed majorly to the green activation strategy. The SEM micrograph of OG@AC was seen to have displayed a leaf-like plate formed by quartz and kaolin. In the batch experimental study, the MB and Cr(Vl) adsorption capacities towards OG@AC were determined to be 227.52 and 143.45 mg/g, respectively. Also, the adsorption kinetics and isotherms models results revealed that the adsorption process of OG@AC towards MB and Cr(Vl) was best described by pseudo-first-order and Freundlich models, suggesting that the adsorption process involves a multilayer physisorption. Moreso, thermodynamic results revealed the adsorption process is feasible, spontaneous, and endothermic in nature. The OG@AC exhibited an outstanding regeneration ability and stability towards MB and Cr(Vl) by maintaining a removal efficiency of 79.11 % and 81.20 % even at the tenth successive adsorption-desorption cycles. Overall, this research sheds more insight on how anthill clay is activated using a feasible design and green chemical ( Ocimum gratissimum leaf extract) to enhance its adsorptive performance towards MB and Cr(Vl), which can broaden its wide application in the real world. • Enhanced OG@AC was developed for MB and Cr(Vl) adsorption. • OG@AC) exhibited an improved BET surface area of 120.48 m2/g. • OG@AC adsorption capacity reached 227.52 and 143.45 mg/g for MB and Cr(Vl). • OG@AC exhibits excellent stability (>75 %) after ten adsorption-desorption cycles.