Preparation of biochar adsorbent from straw and its adsorption capability

In order to find a new way of using discarded biomass materials, the wheat straw was used to prepare biochar adsorbent by means of carbonization at low and middle temperatures. Then, the Cu2+ was taken as adsorbed substance to investigate the biochar adsorbent adsorption capability for heavy metal from the wastewater. The results showed that the biochar adsorbent prepared at low and middle temperatures (200-500℃) obtained higher productivity with less energy consumption, easier process, higher adsorption speed and short time to reach the adsorption equilibrium. At the same time, it was found that the longest time to reach the adsorption equilibrium was 3 h (P200), and the shortest time was just only 0.5 h (P500). The maximum adsorption capacity of P500 could reach to 11.19 mg/g at 30℃. The adsorption kinetic process was consistent with the Lagergren pseudo-second order kinetic model. The adsorption isotherm agreed well with the Langmuir formulae, and the separation factor (RL) located in the range of 0-1 for favored adsorption. The SEM results indicated that the pore deformation and the straw roughness increased as the carbonization temperature rising, which made the pore canal effect easier and the adsorption properties more excellent. The research can provide a reference for engineering application of biomass adsorbent.