Selective adsorption mechanisms of iodinated trihalomethanes onto thiol-functionalized HKUST-1s in a mixed solute

The selective adsorption mechanisms involved in the competitive adsorption of five iodinated trihalomethanes (ITHMs) onto dithiolglycol and (3-mercaptopropyl)-trimethoxy functionalized HKUST-1 (HK-SH and HK-MPTS, respectively) were investigated by single-and mixed-batch adsorption. HK-SH had the highest adsorption rates and capacities for the five I-THMs, followed by HK-MPTS and pristine HKUST-1, even though the porosity and surface area decreased after modification. The primary adsorptive mechanism of HK-SH consists of ion dipole interactions of I-THMs with the protonated hydroxyl and thiol groups at the metal (Cu) node, which is supported by Lewis acid-base reactions via Cu-Cu complex and pi pi interactions. In a mixed solute, bromodiiodomethane, which was the most hydrophobic and had the smallest molecular size, exhibited the most competitive adsorption on HK-SH. In contrast, the selective adsorption of I-THMs onto HK-MPTS was affected by their log K-ow values, causing hydrophobic partitioning onto the alkyl chain of the mercaptopropyl group. Iodinated haloforms tend to achieve a higher adsorption rate and capacity than chlorinated and brominated haloforms via hydrophobic partitioning. Moreover, dithiolglycol grafted onto HK-SH can better promote the excellent selective adsorption performance of iodoacetamide than dichloroiodomethane and iodoacetic acid in both single-and mixed-solute solutions due to hydrogen bonding via the -NH2 group of diiodoacetamide.

Automated summary

This study investigated the selective adsorption mechanisms of five iodinated trihalomethanes (ITHMs) onto modified HKUST-1 materials. It was found that the modified HKUST-1 showed higher adsorption rates and capacities for ITHMs compared to the pristine HKUST-1. The primary adsorptive mechanism of HK-SH involved ion dipole interactions and Lewis acid-base reactions, while the selective adsorption of ITHMs onto HK-MPTS was influenced by their log K-ow values.