Effect of Central Metal Ions of Analogous Metal-Organic Frameworks on Adsorption of Organoarsenic Compounds from Water: Plausible Mechanism of Adsorption and Water Purification

• Published in: Chemistry : a European journal Vol. 21; no. 1; pp. 347 - 354
• Main Authors: Jun, Jong Won, Tong, Minman, Jung, Beom K., Hasan, Zubair, Zhong, Chongli, Jhung, Sung Hwa
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 02.01.2015; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Activated carbon; Activation; Adsorption; Arsanilic Acid - chemistry; arsenic; Chemistry; Coordination Complexes - chemistry; Desorption; Hydrogen-Ion Concentration; Ions - chemistry; iron; Iron - chemistry; Mathematical analysis; Metal-organic frameworks; Metalorganic compounds; Organometallic Compounds - chemistry; Roxarsone - chemistry; Spectroscopy, Fourier Transform Infrared; Surface chemistry; Water Pollutants, Chemical - chemistry; Water Purification; water purification; iron; adsorption; arsenic; metal-organic frameworks
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201404658

The adsorptive removal of organoarsenic compounds such as p‐arsanilic acid (ASA) and roxarsone (ROX) from water using metal–organic frameworks (MOFs) has been investigated for the first time. A MOF, iron benzenetricarboxylate (also called MIL‐100‐Fe) exhibits a much higher adsorption capacity for ASA and ROX than activated carbon, zeolite (HY), goethite, and other MOFs. The adsorption of ASA and ROX over MIL‐100‐Fe is also much more rapid than that over activated carbon. Moreover, the used MIL‐100‐Fe can be recycled by simply washing with acidic ethanol. Therefore, it is determined that a MOF such as MIL‐100‐Fe can be used to remove organoarsenic compounds from contaminated water because of its high adsorption capacity, rapid adsorption, and ready regeneration. Moreover, only one of three analogous MIL‐100 species (MIL‐100‐Fe, rather than MIL‐100‐Al or MIL‐100‐Cr) can effectively remove the organoarsenic compounds. This selective and high adsorption over MIL‐100‐Fe, different from other analogous MIL‐100 species, can be explained (through calculations) by the facile desorption of water from MIL‐100‐Fe as well as the large (absolute value) replacement energy (difference between the adsorption energies of the organoarsenic compounds and water) exhibited by MIL‐100‐Fe. A plausible adsorption/desorption mechanism is proposed based on the surface charge of the MOFs, FTIR results, calculations, and the reactivation results with respect to the solvents used in the experiments. As seen in MOFs: Among three analogous metal–organic frameworks (MOFs; MIL‐100‐Al, MIL‐100‐Cr, and MIL‐100‐Fe), only MIL‐100‐Fe is found to be very effective in the adsorption of organic arsenic compounds from water. This preferential adsorption and the adsorption mechanism can be explained with detailed investigation and calculations on the metal ion sites within the MOFs.