Invasive plant-crofton weed as adsorbent for effective removal of copper from aqueous solution

Abstract

Crofton weed, a noxious invasive plant, was evaluated as a biosorbent for the adsorption of Cu(II) from aqueous solution. Firstly, the physicochemical characteristics of crofton weed biosorbent (CWBS) were determined by chemical and instrumental analyses. Secondly, the batch adsorption experiments of various influence parameters were carried out to investigate the Cu(II) adsorption behaviors by CWBS. Thirdly, the reusability of CWBS was determined by an adsorption–desorption experiment. Lastly, the Cu(II) adsorption mechanisms by CWBS were explored. CWBS had a certain cation exchange capacity (1.05 meq g −1 ), an irregular and rough surface, and abundant functional groups. The pseudo-second-order kinetic model and Langmuir isotherm fitted the adsorption experimental data well, and the maximum Cu(II) adsorption capacity obtained by the Langmuir isotherm was 33.87 mg g −1 at 308 K. Thermodynamics indicated that the adsorption process was spontaneous and endothermic. Moreover, the Cu(II) adsorption efficiency was 50.84% after four adsorption–desorption cycles, indicating that CWBS can be reused. The main Cu(II) adsorption mechanisms by CWBS included ion exchange, coordination with π electrons, and electrostatic adsorption, wherein ion exchange was predominant. Overall, crofton weed can be used as an effective and feasible biosorbent to remove Cu(II) from aqueous solution, which broadens the utilization of crofton weed. • Crofton weed was evaluated as a novel biosorbent (CWBS) to remove Cu(II). • Langmuir isotherm and pseud-second-order kinetic model fitted the Cu(II) adsorption process well. • CWBS had a desired Cu(II) adsorption capacity (33.87 mg g -1 ). • Ion exchange was the predominant adsorption mechanism for the Cu(II) adsorption by CWBS.