海藻酸锆/聚N-异丙基丙烯酰胺半互穿网络凝胶球的除磷性能

利用离子交联和自由基聚合反应制备了一种海藻酸锆/聚(N-异丙基丙烯酰胺)半互穿网络凝胶球(ZA/PNIPAM),用于吸附水中的磷酸盐.考察了溶液初始pH、吸附剂投加量、初始磷酸盐浓度和共存阴离子等因素对凝胶球吸附性能的影响.结果表明:ZA/PNIPAM在pH=2时可获得较大的吸附能力;随着投加量的减少、初始磷酸盐浓度的升高,凝胶球的吸附性能逐渐增大;SO_4~(2-)对吸附性能影响较Cl~-和NO_3~-明显.准二级动力学模型和颗粒内部扩散模型可以较好地拟合动力学吸附数据,表明表面吸附和颗粒内部扩散是吸附速率的主要控制步骤.吸附等温线数据可以较好地被Freundlich模型描述,表明吸附过程为非均匀多分子层吸附.FTIR、XPS、零电荷点(pH_(pzc))的结果以及相关吸附数据揭示凝胶球吸附磷酸盐的机制为静电吸附(物理吸附)以及配位交换(化学吸附)的共同作用.经过4次循环再生后,ZA/PNIPAM吸附性能保持稳定,具有良好的重复使用性.

Phosphate Removal on Zirconium Alginate/Poly(N-isopropyl acrylamide) Hydrogel Beads with a Semi-interpenetrating Network

Zirconium alginate/poly(N-isopropyl acrylamide) hydrogel beads with a semi-interpenetrating network (ZA/PNIPAM) were prepared by using the ionic crosslinking and radical polymerization method and investigated for phosphate removal from aqueous solutions. The effects on the adsorption performance of hydrogel beads, including initial pH, adsorbent dose, initial phosphate concentration, and co-existing anions, were evaluated systematically. Results showed that the ZA/PNIPAM could exhibit a maximum uptake capacity of phosphate at pH 2.The uptake capacity of the adsorbent increased with a decrease in the dose or an increase in the initial phosphate concentration. The presence of SO₄^2- had a more negative effect on phosphate removal compared to Cl^- and NO₃^-. The kinetics fitted a pseudo-second-order model and intraparticle diffusion model, suggesting the adsorption rate was mainly controlled by surface adsorption and diffusion into the interior of the hydrogel beads. The isotherm data could be described by the Freundlich model, indicating that the adsorption process was heterogeneous multilayer adsorption. The studies of FTIR, XPS, and zero point of charge with relevant adsorption data revealed that the phosphate adsorption mechanisms could be electrostatic attraction (physical adsorption) and ligand exchange reactions (chemical adsorption). After four cycles of regeneration, ZA/PNIPAM exhibited a stable uptake capacity, indicating favorable reusability.