Preparation Of The Adsorbent By Wheat Straw And The Study Of Its Adsorption Properties On Cu²⁺ In Aqueous Solution

Based on lots of the related literatures, a series of anionic sorbents were prepared by wheat straw from agriculture residues. In this work the wheat straw was used as biomass to prepare the original adsorbent and the biochar adsorbent respectively by means of physical modification. According to the static and dynamic adsorption experiment, variety of factors to adsorption effect were investigated. In addition, the adsorption balance and the adsorption kinetics were studied systematically. Further more, we had also researched on the regeneration of adsorbent. It will provide some scientific basis for straw biomass scale application on treatment of wastewater. The main contents and results are following:The static adsorption of Cu²⁺ from solution by wheat straw have been studied. Batch adsorption experiment were carried out by considering various dosage of adsorbent, pH of the solution and interaction time. The results showed that the adsorption was strongly dependent on pH of the medium. The kinetics of the interactions showed better agreement with the Lagergren second order kinetics, and the adsorption data showed a good fitting with Langmuir isotherm. The maximum adsorption capacity was 24.6 mg·g^-1.Its separation factors (RL) are in range of 0¹ which showing a favorable adsorption. Wheat straw saturated can be regenerated by HCl of 0.2M under 30℃, and the regeneration of the adsorbent showed a favorable adsorption which is similar with fresh wheat straw.The dynamic adsorption of Cu²⁺ from solution by wheat straw have been studied. In this part, we researched on adsorption and desorption of Cu²⁺ with wheat straw through dynamic adsorption experiments, dynamic desorption experiments and regeneration experiments. The results showed that the influences of influent flow rate and influent metal concentration for the removal of Cu²⁺ from aqueous solutions on wheat straw column were significantly determined. If increased the flow rate, the breakthrough volume will be decreased and the breakthrough time will be increased, the equilibrium adsorption will be decreased while the removal rate of Cu²⁺will be increased. In a certain flow rate, when the initial concentration increased, the equilibrium adsorption of wheat straw for Cu²⁺ will be increased while the removal rate of Cu²⁺will be decreased. If increased pH of solution, the equilibrium adsorption and the removal rate of Cu²⁺will be increased. The ideal conditions of adsorption were:Q=4.395.0mL·min^-1, [Cu²⁺]=43.2mg·L^-1, pH=5.0. The equilibrium adsorption capacity of wheat straw was 1.54mg·g^-1 under the ideal conditions. The adsorbed Cu²⁺ could be easily desorbed from wheat straw with a 0.5mol·L^-1 HCl.In this work the wheat straw was used as biomass to prepare the biochar adsorbent by means of carbonization at low and middle temperatures. We took Cu²⁺ as an example to investigate the adsorption of heavy metal from wastewater by the biochar adsorbent. The results showed that the biochar adsorbent obtained at low and middle temperatures exhibited higher productivity, less energy consumption, higher adsorption speed and less time to reach adsorption equilibrium than that obtained at high temperatures. It took the longest time (3h) for the adsorbent (P200) to achieve adsorption equilibrium, while for the adsorbent (P500) it took the shortest time (only 0.5 h). The maximum adsorption capacity of P500 could reach 11.19 mg·g ^-1 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; the separation factor (R_L) was in the range of 0¹, which favored adsorption. The SEM results indicated that the pore deformation and the roughness of the straw increased with increasing the carbonization temperature.