海藻酸钠/锆@钙水凝胶的制备及其对磷的吸附研究

Preparation of sodium alginate/zirconium@calcium hydrogel and its sorption behavior to phosphate

利用简便的方法制备了一种新型的海藻酸钠/锆@钙(SA/Zr@Ca)水凝胶材料,采用SEM、XRD对该材料进行了表征,并通过拟合吸附等温模型及吸附动力学模型,结合XPS和Zeta电位分析,研究了该材料对磷酸盐吸附的性能和机理.结果表明,该材料为非晶态的无定型材料.在溶液初始pH为2~7时,SA/Zr@Ca对磷酸盐(以PO_(4)^(3-)计)的吸附量均大于60 mg·g^(-1),pH=2时,吸附性能最佳(124.23 mg·g^(-1)).HCO_(3)^(-)、SO_(4)^(2-)和NO_(3)^(-)对SA/Zr@Ca水凝胶吸附磷酸盐的影响不大,其中,NO_(3)^(-)在pH=3的条件下对磷的吸附有轻微抑制作用,在pH为5~7时,则对磷的吸附具有促进作用.吸附动力学过程更符合粒子内扩散模型,吸附热力学过程符合Redlich-Peterson模型,且随温度的升高,反应的ΔG^(θ)降低,说明该吸附过程为自发的混合吸附过程.此外,XPS和Zeta电位分析结果表明,在初始溶液pH低于3.19时,SA/Zr@Ca水凝胶对磷的吸附通过静电吸附和配位交换实现;pH高于3.19时,吸附作用通过配位交换实现.

A novel sodium alginate/zirconium@calcium(SA/Zr@Ca)hydrogel was synthesized by a simple method,and its phosphate adsorption performance and mechanism were investigated.The hydrogel was characterized as an amorphous material by scanning electronic microscopy(SEM)and X-ray diffraction(XRD).The adsorption amount of SA/Zr@Ca for phosphate(calculated by PO_(4)^(3-))was higher than 60 mg·g^(-1) in initial solution pH range of 2~7,of which the best adsorption capacity was found at pH 2 with 124.23 mg·g^(-1).Coexistent ion HCO_(3)^(-),SO_(4)^(2-) and NO_(3)^(-) had a little effects on phosphate adsorption,where NO_(3)^(-) could slightly inhibit the phosphate adsorption process at pH 3,promote at pH 5~7.The phosphate adsorption kinetics course was consistent with intraparticle diffusion model,which indicated that film and intraparticle diffusions occurred simultaneously in the adsorption process.The Redlich-Peterson model could well fit adsorption isotherm data and with the increase of temperature,theΔG^(θ) of adsorption was decreased,indicating that phosphate adsorption was a spontaneous mixed process.In addition,the results obtained by both X-ray photoelectron spectroscopy(XPS)and Zeta-potential showed that SA/Zr@Ca hydrogel adsorbed phosphate via electrostatic attraction and ligand exchange when the initial solution pH value was lower than 3.19,and mainly through ligand exchange when pH value was higher than 3.19.