The fate of wood wastes: from the gasification and its application as adsorbent of textile pollutants

This work reports the use of wood wastes (WWs) to generate clean energy through gasification. WW chips were fed into two gasifiers, which generated 24.7 kWe and 1.2 kWe of electrical energy. Each gasifier generated synthesis gas (CO + H ₂ ) and biochar as solid residue. Furthermore, biochar samples were employed as low-cost adsorbent for textile dyes, and was characterized through porosity (BET), scanning electron microscopy (SEM), thermogravimetry (TGA), infrared spectroscopy (FTIR), X-ray diffraction and point of zero charge techniques. A 2² factorial planning was carried out to investigate the effects of agitation velocity and particle size over the adsorption. Kinetic and equilibrium studies were applied to achieve the adsorption parameters of the biochars: kinetic constant, 0.08–0.54 g/mg/min (for pseudo-second-order model), maximum adsorption capacity 190–192 mg/g and equilibrium time 60 min; the data were compared with commercial activated carbon. Biochar material was pointed as the best alternative from the environmental point of view. This is due to the gasifier capacity to generate greater amounts of energy. Moreover, biochar structure exhibited a great uniformity and although its surface area is smaller than wood residue biochar, the average pores diameter is larger which may end up compensating. Real textile wastewater was collected from laundry effluent and its fate after adsorption onto the three samples of biochars was analyzed through phytotoxicity assessment, which showed germination index varying from 50%– 98%. Therefore, the results were very promising for wood residue biochars, with maximum adsorption capacity (192 mg/g) similarly to commercial activated carbon.