Developing low-cost and high-performance adsorbents is of great significance for the treatment of wastewater containing heavy metal ions. Herein, dodecyl dimethyl betaine modified Na-based montmorillonite (BS-MMT) is successfully prepared by a facile wet method for enhanced lead ion (Pb2+) adsorption. The interlamellar spacing of Na-MMT is effectively regulated ranges from 1.25 to 1.79 nm by changing the ratio of BS-12 content from 5% to 150% (vs. MMT). The Pb2+ capacity adsorption of BS-MMT could reach up to 255.36 mg/g when the usage of BS-12 is 15%. Pb2+ adsorption process on BS-MMT follows the Langmuir model and is endothermic. Mechanism analysis suggests that the main Pb2+ adsorption pathways on BS-MMT include ion exchange, functional group complexation, electrostatic attraction and precipitation by CO3 2  . Moreover, the modification of BS-12 could not only brings carboxyl and amine functional groups to trap of Pb2+ on the surface and interlayer of MMT, but also optimize the layer spacing of MMT since its long carbon chain. This work provides a feasible strategy to optimize the adsorption capacity of organic modified MMT for heavy metals.

Fabricating highly efficient and low-cost absorbents to remove organic contaminants in industrial effluents is urgent yet of great importance. Herein, a facile one-pot hydrothermal approach was developed to successfully construct magnesium silicate and bentonite composite (MS-Bt) with uniform multilayer porous structure by using Bt as structural promoter. The specific surface area of MS-Bt can reach up to 392 m2 center dot g-1 along with an average pore diameter of 2.29 nm and a pore volume of 0.22 cm3 center dot g-1. MS-Bt composite exhibits a maximal adsorption capacity of 253.92 mg center dot g-1 for methylene blue (MB) in model wastewater treatment. Adsorption behavior fitted well with Langmuir isotherm and pseudo-second-order kinetics adsorption equations. The adsorption pathways of MB on MS-Bt mainly include chemical precipitation by Mg-OH, electrostatic attraction and surface hydroxyl functional group capture. This work is anticipated to give a new insight into constructing organic contaminants adsorbent by using clay mineral material as an auxiliary agent.

A zeolitic imidazole framework-8/montmorillonite (ZIF-8/MMT) composite was synthesized by a simple method through in-situ growth of ZIF-8 on MMT for efficient Pb2+ capture from water. The adsorption process of Pb2+ by ZIF-8/MMT composite followed the Langmuir model and the maximum adsorption could reach up to 336.89 mg/ g, which was much better than that of the monocomponent of ZIF-8 (117.78 mg/g) or MMT (85.20 mg/g). Kinetics result suggested that Pb2+ adsorption by ZIF-8/MMT was a pseudo-second-order dynamic process, indicating a chemisorption process dominates. Ion exchange, electrostatic attraction and hydroxyl complexation were main pathways for Pb2+ removal by ZIF-8/MMT composite. The enhanced performance of ZIF-8/MMT composite should be attributed to following points. Firstly, the lamellar structure of MMT was in favor of ZIF-8 nanoparticles grow and disperse uniformly on the surface, thus avoiding the aggregation. Secondly, the pos-itive charge on ZIF-8 was neutralized by the negative charge on the surface of MMT, and thus the adsorption capacity of ZIF-8 for Pb2+ is effectively released. Thirdly, the combination of MMT and ZIF-8 optimized the pore structure, which was favorable for Pb2+ adsorption and diffusion. Therefore, the synthesized ZIF-8/MMT com-posites is a prospective candidate for Pb2+ removal from wastewater.

以河南南部天然钙基膨润土为原料,通过钠化改性得到了钠基膨润土.通过调控吸附剂用量、亚甲基蓝(MB)浓度、吸附时间、溶液pH值和温度,分析对比了天然钙基膨润土(PRT-1)、钙基提纯膨润土(PRT-1T)和钠基膨润土(PRT-1Na)对MB的去除效率.同时,对PRT-1T和PRT-1Na对MB的吸附动力学和吸附机制进行了研究.结果表明,由于PRT-1Na有更大的比表面积、更高的阳离子交换容量和更丰富的羟基结构,表现出对MB更好的吸附效果.在同等吸附条件下,PRT-1Na的吸附效果是PRT-1的4倍,PRT-1T是PRT-1的2倍.在20℃,pH为6,PRT-1Na用量为1.0 g,吸附时间为2 h,MB为500 mL,且初始浓度为500 mg·L-1时,MB去除率高达99.89％.另外,PRT-1Na对MB染料废水的吸附既存在物理吸附也有化学吸附,Elovich模型对PRT-1T和PRT-1Na吸附MB染料废水的过程拟合度均高,但伪一级动力学模型对PRT-1Na拟合效果最好.

Developing efficient and low-cost adsorbent for removing heavy metal ions from aqueous solution is of great significance for environmental protection. Herein, low quality natural bentonite was purified and sodium-modified to adsorb Pb2+ from the aqueous phase. The effects of initial pH value of the solution, type and amount of the adsorbent, contact time and initial Pb2+ concentration on the adsorption performance of sodium bentonite were systematically studied. The adsorption efficiency of sodium bentonite was significantly better than that of purified bentonite and natural bentonite toward Pb2+. Under the optimum adsorption conditions of pH = 5, adsorbent dosage of 0.2 g, initial Pb2+ concentration of 400 mg/L, and adsorption time of 120 min, sodium bentonite can remove more than 99.94% of Pb2+. Adsorption behavior fitted well with Freundlich isotherm and pseudo-second-order kinetics adsorption equations. Adsorption process was endothermic and feasible. The adsorption pathways of Pb2+ on sodium bentonite are mainly including ion exchange, surface hydroxyl functional group capture, electrostatic attraction and chemical precipitation by CO32- in the pore channel to form PbCO3. This research is anticipated to give technical support for prompting the wider application of bentonite as an adsorbent material.