粉煤灰微波改性及其对甲基橙的吸附性能

Coal fly ash modified by microwave irradiation and its adsorption behavior for methyl orange from aqueous solution

将取自于热电厂的粉煤灰(FA)球磨5h得到超细粉煤灰(UFA),再经过微波处理得到微波辐照改性超细粉煤灰(MFA),并研究其对水溶液中甲基橙的吸附性能。动力学研究结果表明,改性粉煤灰对甲基橙的吸附符合二级吸附动力学模型,通过模型计算出的FA,UFA和MFA的二级吸附速率常数(k2)分别为9.30×10-3,13.00×10-3,18.35×10-3g.mg-1.min-1;热力学研究结果表明,吸附过程可以用Langmuir方程描述。计算吸附热力学参数ΔG,ΔS和ΔH,FA,UFA和MFA对甲基橙的吸附焓(ΔH)分别为-23.03,-25.98和-29.42kJ·mol-1。ΔG和ΔH均为负值,表明吸附为一自发的放热过程。

Coal fly ash （FA） collected from a thermoelectricity power station was ball milled for 5 h and got ultra-fine coal fly ash （UFA）. UFA was modified by microwave irradiation and then obtained modified ultrafine coal fly ash （MFA）. The adsorption behavior and mechanism of methyl orange adsorption onto FA, UFA and MFA were studied. Kinetic studies showed that methyl orange adsorption onto modi- fied coal fly ash fitted the second-order kinetic model. The second-order rate constants （k2 ） calculated from the equation were 9.30 10^-3, 13.00 10^-3 and 18.35 10^-3 g·mg^-l min^-l for FA, UFA and MFA, respectively. Isotherm studies illustrated that adsorption could be described by Langmuir isotherm model. The adsorption thermodynamic parameters such as change in free energy （△G）, enthalpy （ △H）, entropy （△S） were also determined. Values of AH for methyl orange adsorption on FA, UFA and MFA were - 23.03, - 25.98 and - 29.42 kJ·mol^-1, respectively. The negative value of △G and △H indicated the adsorption process was spontaneous and exothermic.