Low-cost biosorbents from pines wastes for heavy metals removal from wastewater: adsorption/desorption studies

The use of inexpensive materials such as agricultural by-products and industrial waste has received considerable attention because of their high efficiency for heavy metal retention, low cost and availability. This study aimed to investigate the technical feasibility of residual biomass from pines (cones and leaves) for Cr(VI) and Cu(II) removal from aqueous solutions. The effect of various parameters, such as pH, metal concentration, contact time, temperature and biosorbent/solution ratio was examined. Biosorbents were characterized using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy. The specific surface area was evaluated by the Brunauer-Emmett-Teller isotherm. The equilibrium data showed better fitting to the Langmuir model, indicating the monolayer adsorption behavior. The Langmuir model predicted a maximum adsorption capacity of 27.78 mg g(-1) of Cu(II) on pine cones and 64.04 mg g(-1) of Cr(VI) on pine leaves. The kinetic study revealed that the pseudo-second-order model fitted the experimental data. The thermodynamic study showed that the biosorption process was endothermic for Cu and exothermic for Cr(VI). The biosorbent can be reactivated with 0.1 mol L-1 HNO3 allowing the recovery of the metals and the recycling of the biosorbent. These results showed that pine waste materials can be used as efficient, economic and eco-friendly biosorbent for Cu(II) and Cr(VI) recovery from contaminated effluents.