Isothermal, kinetic, thermal, and economic characteristics of NaOH-modified charred–desiccated coconut waste as adsorbent for lead (II) in water phase

다국어 초록 (Multilingual Abstract)

In this study, charred–desiccated coconut waste was treated with several chemicals, such as NaOH,NaOCl, H2O2, and HNO3, to prepare chemically modified adsorbents. Fourier transform infrared spectroscopyrevealed that chemical modification enhanced the surface chemistry of the adsorbent by introducingnew functional groups and increasing their concentration. The chemically modified adsorbentshad lower surface areas of 0.13–17.36 m2/g, which were substantially lower than that of the pristineadsorbent. Regardless of the surface area, all modified adsorbents exhibited higher Pb(II) adsorptioncapacities, wherein that of desiccated coconut-waste char (DCWC)-NaOH was the highest, with a removalefficiency of 96% (Q = 29.854 mg/g) for an adsorption time of 1 min. The equilibrium and kinetic data forthe DCWC-NaOH adsorbent best fit the Freundlich isotherm and pseudo-second-order kinetic models,respectively, with a maximum monolayer adsorption capacity of 1666.67 mg/g. The adsorption of Pb(II) ions was an exothermic process, with an optimum temperature of 40 C. Compared to existing commercialadsorbents, the proposed adsorbent was highly regenerable and considerably low-cost, showingpromising potential for commercial applications.