Yu Xiaolong, Zhang Juan, Zheng Yan
State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China; Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China; College of Environmental Sciences and Engineering, Nankai University, Tianjin 300350, China.
State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China; Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
Sci Total Environ. 2021 Mar 20;761:143236. doi: 10.1016/j.scitotenv.2020.143236. Epub 2020 Oct 26.
Perchlorate (ClO) in water is an emerging contaminant that threatens human health by inhibiting the uptake of iodine in the thyroid gland. Biopolymer adsorbents including chitosan hydrogel beads (CSBs) have attracted increasing attentions in water treatment for their low costs, ease in preparation, and environmental friendliness. However, the adsorption capacity for ClO by several crosslinked CSBs has been shown to be low. To overcome this, epichlorohydrin (ECH) crosslinked CSBs (ECH-CSBs) that preserved -NH functional groups as potential sites for adsorption are synthesized and characterized, followed by batch adsorption experiments to evaluate adsorption and desorption reactions. The point of zero charge is determined to be 5.1 ± 0.1. Both XPS spectra and DFT calculations support that electrostatic interaction between ClO and protonated -NH functional groups is responsible for adsorption that reaches a capacity of 63.4 to 76.3 mg/g between pH of 4.0-10.0 at 303.15 K that follows Langmuir isotherm. ECH crosslinking also enhances hydrophilicity of CSBs to allow for increased adsorption for ClO. Adsorption of ClO (10 and 100 mg/L) follows a pseudo-first order kinetics with equilibrium time of 2-6 h but is limited by intra-particle diffusion. Anions common in natural waters exhibit interference effects due to similar electrostatic attraction mechanism, thus HCO and SO with high abundance in natural waters need pre-treatment. Regeneration of the adsorbents to 100% of its adsorption capacity by rinsing with 0.1 M NaOH is demonstrated for 12 cycles due to complete desorption of ClO via electrostatic repulsion, assuring reusability.
水中的高氯酸盐（ClO）是一种新出现的污染物，它通过抑制甲状腺对碘的摄取来威胁人类健康。包括壳聚糖水凝胶珠（CSBs）在内的生物聚合物吸附剂因其成本低、易于制备和环境友好等特点，在水处理中受到越来越多的关注。然而，几种交联CSBs对ClO的吸附容量已被证明较低。为了克服这一问题，合成并表征了保留 -NH官能团作为潜在吸附位点的环氧氯丙烷（ECH）交联CSBs（ECH-CSBs），随后进行批量吸附实验以评估吸附和解吸反应。零电荷点测定为5.1 ± 0.1。XPS光谱和DFT计算均支持ClO与质子化 -NH官能团之间的静电相互作用是吸附的原因，在303.15 K、pH值为4.0 - 10.0的条件下，吸附容量达到63.4至76.3 mg/g，符合朗缪尔等温线。ECH交联还增强了CSBs的亲水性，从而增加了对ClO的吸附。ClO（10和100 mg/L）的吸附遵循准一级动力学，平衡时间为2 - 6小时，但受颗粒内扩散限制。天然水中常见的阴离子由于类似的静电吸引机制而表现出干扰效应，因此天然水中高丰度的HCO和SO需要预处理。通过用0.1 M NaOH冲洗，吸附剂可在12个循环中再生至其吸附容量的100%，这是由于ClO通过静电排斥完全解吸，确保了可重复使用性。
