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This work aims for the development and characterization of a new biosorbent with enhanced capacity for recovery of Cr(III) from aqueous solutions. The adsorbent was developed by chemical modification of pine bark (Pinus pinaster) (PB). Initially, several chemical agents (HCl, H2SO4, HNO3, H3PO4, citric acid, acetic acid, NaOH) were tested, but the best results were obtained with NaOH. The adsorbent developed was characterized regarding chemical composition and thermal behaviour before and after adsorption tests. Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) showed the morphology and the most relevant elements on the surface before and after adsorption of Cr(III). Fourier transform infrared spectroscopy (FTIR) revealed the important role of carboxylate groups in Cr(III) uptake. The adsorption process was studied under different conditions, namely for testing the particle size (in the ranges from 0.088 to 0.149 and 0.250 to 0.595 mm). The equilibrium isotherms showed that Cr(III) adsorption is strongly dependent on particle size. According to the Langmuir model, the maximum adsorption capacity of Cr(III) increased from 17.15 to 31.40 mg/g as the particle range decreased. The experimental Cr(III) removal efficiencies as a function of the adsorbent dosage were well predicted by the mass balance equation for the batch adsorption process coupled with the equilibrium isotherm. This article is protected by copyright. All rights reserved

Compost from poultry hatchery waste (CPHW) was used as an efficient biosorbent for the removal of heavy metals from aqueous solutions. Single and competitive adsorption of Cd(II) and Pb(II) onto CPHW were studied. The optimum pH of the aqueous solution for Cd(II) and Pb(II) adsorption was found to be in the range 3 to 5. The pseudo-second order model enabled a better description of the adsorption kinetics. Equilibrium data obtained at 25, 35, and 45 °C were better described by the Sips isotherm than by the Freundlich and Langmuir models. The maximum adsorption capacities calculated by applying the Sips isotherm were 32.3 mg/g for Cd(II) and 142.6 mg/g for Pb(II) at 25 °C. In binary metal ion solutions, a decrease in the adsorption capacity for both heavy metals was observed. The single and competitive adsorption tests revealed that the adsorption affinity was higher for Pb(II) than for Cd(II). Thermodynamic parameters such as ΔG0, ΔH0, and ΔS0 indicated that the adsorption was feasible, spontaneous, and endothermic. FTIR spectroscopy characterization showed that carboxyl and hydroxyl groups were involved in the adsorption of the metals. SEM-EDX analysis confirmed that Cd(II) and Pb(II) may replace Ca(II) from biosorbent surface. Therefore, the results suggest that CPHW can be used as an economical biosorbent for Pb(II) and Cd(II) removal from aqueous solutions.