氨基功能化纳米复合材料对磷酸盐的吸附研究

Adsorption Studies on Phosphate by Amino-functionalized Nano-size Composite Materials

合成了4种氨基(乙二胺(EDA),二乙烯三胺(DETA),三乙烯四胺(TETA)和四乙烯五胺(TEPA))功能化纳米复合材料(NH2-NCMs,分别命名为EDA-NCMs,DETA-NCMs,TETA-NCMs和TEPA-NCMs).采用FTIR(傅立叶变换红外光谱分析),TG/DTG(热重差热分析),XPS(X-射线光电子能谱分析)等手段对其进行了表征,并考察了其对水中磷酸盐的吸附性能.结果表明:溶液pH对其吸附性能影响较大,在pH为2.5的条件下,4种吸附剂对磷酸盐的吸附效果最佳;在5min内即可达到平衡吸附量的90%;4种吸附剂对磷酸盐的吸附均符合Langmuir等温吸附模型;吸附行为均符合准二级速率模型;吸附反应为自发进行的放热反应和熵减的过程;推测其吸附机理以静电作用力为主.4种吸附剂用于磷酸盐含量为50 mg/L的废水处理的吸附率均大于97%,均达到一级A出水的排放标准(≤1.53 mg/L,以3PO4-计).

Four kinds of amino-functionalized nano-size composite materials（NH2-NCMs） were prepared firstly by radical co-polymerization,of which methylmethacrylate（MMA） and glycidylmethacrylate（GMA） acted as monomers and benzoyl peroxide（BPO） acted as initiator,to obtain epoxyl-functionalized polymers and then modified by ethanediamine（EDA）,diethylenetriamine（DETA）,triethylenetetramine（TETA）,or tetraethylenepentamine（TEPA）,named as EDA-NCMs,DETA-NCMs,TETA-NCMs and TEPA-NCMs,respectively.They were fully characterized by Fourier-transformed infrared spectroscopy（FTIR）,thermogravimetry and differential analyses（TG/DTG）,and X-ray photoelectron spectroscopy analysis（XPS）.The NH2-NCMs were used as phosphate adsorbents to remove phosphate in water.Effects of pH values,initial concentration of phosphate,adsorption time,adsorption temperature and type of functional amines were studied.To investigate the effects of pH value of solutions on adsorption,40 mL of 200 mg/L phosphate solutions with pH ranging from 1.5 to 7.0 were mixed with 0.05 g NH2-NCMs for 12 h.The adsorption capacities were investigated at pH 2.5,with 0.05 g NH2-NCMs by varying the initial phosphate concentration from 50 to 800 mg/L at 308 K.Adsorption kinetic studies were investigated at pH 2.5,by adding 0.05 g NH2-NCMs into 40 mL 200 mg/L phosphate solutions at 308 K with contacting time ranging from 1 min to 180 min.Results indicated that the adsorptive properties of the four kinds of NH2-NCMs were highly pH dependent and reached optimum at pH 2.5.Adsorption processes reached 90% of the equilibrium within 5 min.The adsorption data of the NH2-NCMs were well fitted with the Langmuir isotherm.The maximum adsorption capacity calculated from Langmuir isotherm was 142.85,156.25,172.41 and 196.08 mg/g for EDA-NCMs,DETA-NCMs,TETA-NCMs and TEPA-NCMs,respectively.Thermodynamic studies suggested that the adsorption processes of phosphate were exothermic（ΔH〈0）,entropy disfavored（ΔS〈0）,and spontaneous（ΔG〈0） in nature.The adsorption mechanism of phosphate could be mainly related with electrostatic interaction.By using the present NH2-NCMs to treat phosphate contained wastewater at concentration of 50 mg/L,the adsorption efficiencies for phosphate can be reached to more than 97% with the residue concentration of phosphate less than 1.16 mg/L,which reached the national criterion of drainage（≤1.53 mg/L,3 PO4-）.