Adsorption of Cu2+ ions by polyurethane-type rigid foam produced from peanut shell

Polyurethane-type rigid foam produced from peanut shell (peanut shell-based polyurethane foam (PSPUF)) was used as an adsorbent for the removal of Cu2+ ions from aqueous solution. The effects of contact time, solution pH, and temperature on the adsorption were investigated at a constant concentration of Cu2+ ions. The equilibrium time of the adsorption was determined as 60 min. The maximum adsorption for Cu2+ ions onto the PSPUF was revealed to be between 597.75 and 632.63 mg g(-1) under all the experimental conditions such as contact time, solution pH, and temperature. The distribution coefficients for Cu2+ ions adsorbed onto the PSPUF were found to be between 781 and 984 L kg(-1) for all the pH and temperatures. The distribution coefficients indicated that Cu2+ ions could be adsorbed by extraction from aqueous solution. Adsorption kinetics followed the pseudo-second-order and the intraparticle diffusion models. The negative values of Gibbs free energy change (Delta G degrees) showed spontaneous nature of the adsorption. The value of 2.68 kJ mol(-1) of the standard enthalpy change of the adsorption (Delta H degrees) indicated a physical adsorption. The positive value of 17.32 J mol(-1)K(-1) of the standard entropy change of the adsorption (Delta S degrees) showed a randomness adsorption of Cu2+ ions onto the PSPUF surface. Moreover, Fourier transform infrared, scanning electron microscopic, and the intraparticle diffusion studies indicated a surface adsorption of Cu2+ ions onto the PSPUF.