Green biomass-derived from Carpobrotus edulis plant for the removal of emerging pollutant and its adsorption mechanism

Abstract

In this paper, the plant Carpobrotus edulis was used in its natural form as a new, cost-effective, and environmentally friendly biosorbent. The adsorption performance of this biomaterial for crystal violet, a cationic dye, was subsequently investigated. The biomaterial was characterized using SEM-EDX, mapping, BET, FT-IR, and pH z analyses, and the effect of the initial concentration (20–1000 mg/L) and temperature (298–308 K) on adsorption efficiency was studied in a batch process. Based on the obtained results, the adsorption mechanism of CV on the biosorbent fit well with the Langmuir isotherm model (q m,exp ≈ q m,cal = 86.95 mg/g). Thermodynamic parameters revealed negative enthalpy (-8.72 kJ/mol), negative Gibbs free energy (-17.31 kJ/mol), and negative entropy (-28.84 J/K·mol), indicating that the adsorption process is energetically favorable, exothermic, and spontaneous. The mechanism of CV adsorption on the biomaterial surface was explained by hydrogen bonding and electrostatic interactions. According to regeneration data, the biosorbent retained 57.5 % uptake capacity for CV dye after four desorption-adsorption cycles. This study demonstrates the potential of using native plants as eco-friendly biosorbents for removing cationic dyes from wastewater. • The specific surface area and pH z of the green local natural plant were 2.08 m 2 /g and 7.6, respectively. • Langmuir isotherm was best obeyed model and the maximum adsorption amount is 86.95 mg/g for CV at 298 K. • The results of the adsorption-desorption tests indicated that the biosorbent is capable of reuse up to four cycles. • The adsorption was spontaneous, exothermic and accompanied by decrease of entropy. • The biomass can be used as cost-effective adsorbent for the removal of hazardous dyes in wastewater treatment.

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