改性镍铁渣吸附剂对Cr(VI)吸附性能的影响及机理分析

以镍铁渣为原料,加入硝酸和表面活性剂对其矿物相改性,制备改性镍铁渣吸附剂,考察表面活性剂种类、十六烷基三甲基溴化铵(CTAB)掺量、吸附剂掺量、溶液初始pH值、Cr(VI)浓度对Cr(VI)吸附效果的影响。结果表明:镍铁渣经改性后可制得结构疏松、比表面积高达180.6 m²/g的无定形SiO₂;改性镍铁渣对Cr(VI)的吸附率在10 min内可达到90%,吸附等温线符合Langmuir模型,最大理论吸附容量为42.55 mg/g,吸附动力学符合拟二级动力学模型。改性镍铁渣吸附剂对Cr(VI)的吸附机理主要是物理吸附和氧化还原,即吸附剂表面范德华力将HCrO ^-₄吸附至吸附剂表面,CTAB提供的电子对将Cr(VI)还原为Cr(III)。对镍铁渣改性获得的高比表面积无定形SiO₂不仅可以有效吸附净化Cr(VI),同时可以实现镍铁渣资源化利用,达到以废治污的目的,具有良好的环境效应和经济效益。

Effect and Mechanism Analysis of Modified Ferronickel Slag Adsorbent on Cr(VI) Adsorption Performance

Using ferronickel slag as raw material, adding nitric acid and surfactant to modify its mineral phase, a modified ferronickel slag adsorbent was prepared, and the effects of surfactant type, cetyltrimethylammonium bromide (CTAB) dosage, adsorbent dosage, initial pH value of solution, Cr(VI) concentration on Cr(VI) adsorption were investigated. The results show that amorphous SiO₂ with loose structure and high specific surface area of 180.6 m²/g is prepared from ferronickel slag after modification. The adsorption rate of modified ferronickel slag on Cr(VI) reaches 90% within 10 min. The adsorption isotherm conforms to the Langmuir model, the maximum theoretical adsorption capacity is 42.55 mg/g, and the adsorption kinetics conforms to the pseudo-second-order kinetic model. The adsorption mechanism of Cr(VI) by modified ferronickel slag adsorbent is mainly physical adsorption and redox, that is, the Van der Waals force on the surface of adsorbent adsorbs HCrO ^-₄ to the surface of adsorbent, and the electron pair provided by CTAB reduces Cr(VI) to Cr(III). The amorphous SiO₂ with high specific surface area obtained by modified ferronickel slag can not only adsorb and purify Cr(VI) effectively, but also realize the resource utilization of ferronickel slag to achieve the purpose of treating pollution with waste, and has good environmental effects and economic benefits.