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Keywords:Copper(II) and zinc(II) Muskmelon peel biochar Langmuir Pseudo-second order Exothermic a b s t r a c tThe muskmelon peel, an abundant common food waste material, has been gainfully utilized for the production of biochar. The biosorptive characteristics of muskmelon peel biochar towards copper(II) and zinc(II) from water are investigated. The biochar is characterized by infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) studies. The various process parameters for the removal of copper(II) and zinc(II) using biochar are optimized. The maximum biosorption of Cu(II) and Zn(II) is attained at pH 7. Maximum Langmuir adsorption capacity (q m ) are 78.74 for copper(II) and 72.99 mg/g for zinc(II) at 303 K. Langmuir isotherm is found to best fit the equilibrium data indicating homogeneous adsorption of metal ions onto the biochar surface. The pseudo-second order kinetic model describes the data best indicating adsorption of one molecule of metal ions onto two surface sites. Thermodynamic parameters suggest the adsorption process to be spontaneous and exothermic. Both liquid-film and intra-particle diffusions controll the overall kinetics of the adsorption process. Biochar proved to be an inexpensive and efficient adsorbent for the removal of titled metals from liquid phase. Ó 2017 Mansoura University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

In this study, the adsorption efficiency of epichlorohydrin modified fresh water green algal biomass was assessed for Pb(II) and Cd(II) uptake from aqueous solution. The process parameters such as contact time, dose, initial metal concentration, solution pH and temperature were optimized. The Langmuir, Freundlich, Temkin and Dubnin-Redushkevich isotherm model was applied to the equilibrium data, which best fitted the Langmuir isotherm indicating homogenous distribution of adsorption sites. The monolayer adsorption capacity was 100.00 for Pb (II) and 72.46 mg/g for Cd(II) adsorption. The kinetic data was best described by pseudo-second order model, with intraparticle and liquid film diffusion controlled mechanism. The negative values of Gibbs free energy change (ΔG º ) and positive enthalpy change (ΔH º ) showed that adsorption process was spontaneous and endothermic. The functional groups, surface morphology and elemental composition of adsorbent, before and after adsorption, was evaluated using FTIR spectra, SEM and EDS studies. The study revealed that the modified algal biomass can effectively and efficiently remove the title metal ions from aqueous solution.