粉煤灰微波改性及其对Cr^(6+)的吸附特性

Modification of microwaved coal fly ash and its adsorption properties for Cr^(6+)

将粉煤灰(fly ash,FA)微波辐照制得微波改性粉煤灰(MFA),选择用H2SO4、NaOH和Ca(OH)2对MFA进行化学改性制得微波化学改性粉煤灰(MMFA),结果表明,用2 mol/L NaOH并按与MFA的质量体积比为1∶4制得的MMFA对Cr6+的吸附去除效果最好,与原灰相比,去除率显著增强。研究了NaOH改性MMFA对废水中Cr6+的吸附性能。动力学研究结果表明,MMFA对Cr6+的吸附动力学符合二级吸附动力学速率方程,吸附受颗粒内扩散过程控制。热力学研究结果表明,在25、35和45℃下MMFA对Cr6+的等温吸附行为均可用Langmuir方程、Freundlich方程和线性方程描述,所得热力学参数吸附自由能(ΔG)、吸附焓(ΔH)和吸附熵(ΔS)均为负值,说明MMFA对Cr6+的吸附过程为自发进行的放热吸附过程。

Raw fly ash（FA） was modified by microwave irradiation and microwaved fly ash（MFA） was obtained,and then H2SO4,NaOH and Ca（OH）2 were added into MFA and further modified microwaved fly ash（MMFA） was prepared.The results showed that MMFA prepared under the condition of MFA mass and 2 mol/L NaOH volume ratio of 1∶ 4 had the best adsorption effect for Cr6＋ and removal rate enhanced markedly,comparing with FA.Adsorption properties of Cr6＋ onto MMFA modified by NaOH were researched.Kinetic studies indicated that the adsorption process kinetics of Cr6＋ on MMFA fitted the second-order adsorption kinetic model and adsorption processes was controlled by intra-particle diffusion.Isotherm studies illustrated that the adsorption under different temperatures followed Langmuir,Freundlich and Linear equations and corresponding thermodynamic parameters of the adsorption process such as free energy（ΔG）,enthalpy（ΔH） and entropy（ΔS） were also determined,and their values were all negative which indicated the adsorption process was a spontaneous and exothermic proces