Swift adsorption of mercury(II) and industrial anionic dye contaminants from aqueous solutions utilizing raw potato peels: performance, isotherm, kinetic, and thermodynamic assessment
摘要
This study investigates the feasibility of utilizing raw potato peels (RPP), an abundant agricultural waste, as a low-cost and sustainable biosorbent for the removal of mercury(II) ions (Hg2+) and methyl orange (MO) dye from aqueous solutions. The motivation stems from the pressing need for effective wastewater treatment methods capable of eliminating hazardous heavy metals and synthetic dyes that pose serious environmental and public health risks. Experimental conditions were optimized for maximum adsorption efficiency: for Hg2+, the optimal parameters were an initial concentration of 600 mg/L, 0.2 g of RPP, 100 min of contact time, and pH 6.02; for MO, optimal removal occurred at 500 mg/L dye concentration, 0.2 g of RPP, 100 min, and pH 3.15. All tests were conducted using a 25 mL working solution. The maximum adsorption capacities of RPP increased with temperature, indicating endothermic behavior. For Hg2+, capacities were 71.94 mg/g (298 K), 86.21 mg/g (308 K), and 107.53 mg/g (318 K); for MO, values were 80.64 mg/g, 90.09 mg/g, and 104.16 mg/g, respectively. Kinetic studies revealed that the adsorption followed a pseudo-second-order model, suggesting chemisorption as the rate-limiting step. Thermodynamic parameters further confirmed spontaneous and endothermic adsorption: for Hg2+, ΔHo = 8.314 kJ/mol, ΔSo = 107.558 J/mol.K, and ΔGo ranged from − 23.738 to − 25.889 kJ/mol; for MO, ΔHo = 33.256 kJ/mol, ΔSo = 195.661 J/mol.K, and ΔGo ranged from − 25.051 to − 28.964 kJ/mol. The calculated activation energies (Ea) were 8.322 kJ/mol for Hg2+ and 12.863 kJ/mol for MO, aligning with the observed temperature dependence and endothermic nature of the process. Overall, the results establish RPP as an effective, sustainable, and environmentally benign biosorbent with significant potential for practical applications in water treatment and environmental remediation, particularly for the dual removal of heavy metals and dyes from contaminated water systems.