氯化钙活化稻草秸秆生物质炭的制备工艺及其吸磷性能研究

Preparation of rice straw-derived biochar( RB ) activated by CaCl_2 and its adsorption on phosphorus

在大多数生态系统中,磷(P)元素是植物生长的限制性元素,也是造成水体富营养化的主要原因.而水体中P的去除方法中尤以吸附法的研究和应用最为广泛.本文以稻草秸秆为原料,Ca Cl2(质量分数10%)为活化剂制备活性生物质炭,作为控制农业面源污染的吸P材料.通过控制稻草秸秆炭制备的炭化温度、浸渍比等工艺条件及溶液初始P浓度、吸附时间、秸秆炭用量、干扰离子、pH等试验条件,研究改性稻草秸秆炭吸P性能及其吸附机理.试验结果表明:在考虑经济性的前提下,稻草秸秆炭吸P性能最优的制备工艺条件为:炭化温度为700℃,浸渍比(m稻草∶m氯化钙)为1∶0.5;改性稻草秸秆炭处理含10 mg·L-1PO3-4-P(以P计)水样,P去除率可达到97%,溶液pH从6.87升至9.52;对稻草秸秆炭对P的吸附情况采用Langmuir和Freundlich吸附模型进行拟合,R2可分别达到0.947和0.892,说明其主要为单分子层化学吸附;此外,根据溶液的pH和P浓度的变化情况,推测P的吸附主要由离子交换实现,即PO3-4-P(主要为H2PO-4)取代结合在Ca离子上的氢氧根而被吸附,秸秆炭上的氢氧根释放,水样pH值上升.

Phosphorus（ P） is a limiting nutrient for plant growth in most ecosystems and a major factor for eutrophication. In the past several decades,the P removal from waste water systems has received great attention. In this paper,a rice straw-derived biochar（ RB） activated by CaCl2（ wt = 10%） was prepared for P removal from P-contained solution. The preparation conditions（ including carbonization temperature and immersion rate（ mrice straw/mCaCl2）） and experimental parameters（ including RB pack levels,adsorption time,interference ion,and initial pH of aqueous solution） were studied.Results showed that in consideration of economy,the optimal RB preparation conditions were found at carbonization temperature of 700 ℃ and immersion rate of 0. 5; Under middle initial P loading rates（ 10 mg·L（-1）,based on P）,the P removal efficiency could reach 97%,and the pH of solution increased from 6. 87 to 9. 52. The P adsorption equilibrium fit well both with the Langmuir isotherm（ R2= 0. 947） and Freundlich isotherm（ R2= 0. 892）. The change of pH values and the adsorption process suggested that ion exchange was possibly the mechanism of phosphate ions adsorption by RB.