镁改性泡沫炭对水中镉(Ⅱ)的吸附性能及去除机理

Adsorption performance and removal mechanism of Cd(Ⅱ) in water by magnesium modified carbon foam

以酶解木质素液化产物树脂(LP树脂)为前驱体,借助微波加热和直接混合法,成功制得了镁改性泡沫炭(Mg/CF)吸附材料,通过红外光谱、X射线衍射、X射线光电子能谱等对其结构性能进行了分析表征,并借助静态吸附实验对其水中Cd(Ⅱ)的脱除性能进行了考察。结果表明,负载于CF表面的镁以MgO纳米颗粒的形式集中分布于CF的泡孔孔壁上,MgO的负载并未减少CF的比表面积,但可使其微孔孔容增大。该吸附材料对水中Cd(Ⅱ)表现出优越的脱除性能,与单独使用MgO相比,Mg/CF对Cd(Ⅱ)的理论最大吸附容量可达308.51 mg·g^(-1),约为MgO的2.0倍,且平衡吸附时间为720 min,较MgO明显缩短。Mg/CF对Cd(Ⅱ)的去除过程满足准二级动力学方程、Langmuir吸附等温线模型,且去除过程为吸热熵增的自发过程。去除机理研究表明,Mg/CF对Cd(Ⅱ)的去除是以离子交换和沉淀等化学作用为主,并伴有物理吸附的过程。

This study displayed a preparation method of efficient and environmentally friendly adsorbent for the removal of Cd(Ⅱ)from water.By directly mixing the modifier Mg(NO3)2 with the precursor resin derived from enzymatic hydrolysis lignin liquefied product resin(LP resin),followed by microwave-foaming and carbonization,a magnesium-modified carbon foam(Mg/CF)was successfully fabricated.The surface functional groups and phase composition of Mg/CF composite adsorbent material were analyzed using an infrared spectrum,X-ray polycrystalline diffractometer,X ray photoelectron spectroscopy,and other characterization methods.The results revealed that the loaded MgO was evenly distributed on the cell wall of carbon foam in the form of nanoparticles after carbonization.The presence of MgO had a negligible effect on the specific surface area of carbon foam but increased the micropore volume instead.Furthermore,to evaluate the Cd(Ⅱ)removal ability of Mg/CF composite in water,batch adsorption experiments were carried out.The findings indicated that this adsorbent exhibited excellent removal ability for Cd(Ⅱ)in water,with a theoretical maximum adsorption capacity of 308.51 mg·g^(-1),which was approximately 2.0 times as neat as MgO adsorbent.Further,the equilibrium time(12 h)of this adsorbent was significantly shorter than that of MgO(24 h).Meanwhile,the thermodynamic analysis showed that the Cd(Ⅱ)removal was a spontaneous,endothermic,and entropy-increasing process.The removal behavior of Mg/CF for Cd(Ⅱ)satisfied the pseudo-secondorder kinetic equation and Langmuir adsorption isotherm model.It was proposed that the Cd(Ⅱ)removal by Mg/CF composite adsorbent could be mainly attributed to ion exchange and chemical precipitation,accompanied by physisorption.