Isotherms, kinetics and thermodynamic studies of adsorption of Cu~(2+) from aqueous solutions by Mg~(2+)/K~+ type orange peel adsorbents

摘要

Orange peel (OP) was used as raw material to prepare two novel adsorbents: MgOP (Mg~(2+) type orange peel adsorbent) and KOP (K~+ type orange peel adsorbent). FT1R and SEM were used to characterize the adsorbents. Effects of pH, solid/liquid ratio, time and metal ion concentration on the Cu~(2+) adsorption by these two adsorbents were investigated. The isotherms data were analyzed using the Langmuir, Freudlich, Temkin and Dubinin-Radushkevich models. Langmuir model provides the best correlation for the adsorption of Cu~(2+) by both MgOP and KOP, and the mono-layer adsorption capacity for Cu~(2+) removal by MgOP and KOP are 40.37 and 59.77 mg/g, respectively. The adsorbed amounts of Cu~(2+) increased with the increase in contact time and reached equilibrium within 20 min. The kinetics data were analyzed using four adsorption kinetic models: the pseudo-first and second-order equations, the Elovich equation and intraparticle diffusion equation. Results show that the pseudo-second-order equation fits the experimental data very well. Thermodynamic studies showed the spontaneous and exothermic nature of the adsorption of Cu~(2+) by MgOP and KOP.