A high activity adsorbent of chemically modified Cucurbita moschata (a novel adsorbent) for the removal of Cu(II) and Ni(II) from aqueous solution: Synthesis, characterization and metal removal efficiency

Remarkable adsorption potential towards Cu(II) and Ni(II) ions from wastewater under competitive sorption conditions was shown by alkali treated Cucurbita moschata biomass (ATCMB). The improvement in the adsorption properties of Cucurbita moschata biomass on treatment was because of the increase in the acidic functional groups on the surface of the adsorbent due to the chemical reaction taking place between sodium carbonate and lignocellulosic material. The alkali treatment of the adsorbent is simple and less time consuming as compare to other methods like physical activation such as the steam pyrolysis, etc. The influence of independent parameters, viz contact time, initial metal ion concentration, pH and adsorbent dosage on the process was investigated. The equilibrium equations were extensively investigated and found to be efficiently represented by Langmuir, Freundlich and Temkin isotherm models at different temperatures. Kinetic studies showed better applicability of second order kinetic model. The thermodynamic parameters (ΔH⁰ and ΔG⁰) suggest that adsorption of Cu(II) and Ni(II) ions was endothermic and spontaneous. The practical efficiency of ATCMB was demonstrated by removing Cu(II) and Ni(II) from single and binary-metal systems by column process. The breakthrough capacities of Cu(II) and Ni(II) ions in single metal system were higher than in binary-metal system. The desorption studies of Cu(II) and Ni(II) ions with 0.1 M HCl were conducted by column process. Therefore, these methods were further used for the extraction and pre-concentration of Cu(II) and Ni(II) ions from solutions of these metal ions prepared in DDW and in tap water for their determination using Atomic absorption spectrometry. Hence the highly efficient alkali treated Cucurbita moschata biomass showed rapid uptake of Cu(II) and Ni(II) indicating that it could be an excellent alternative for the removal of heavy metals by sorption process.