Organic-inorganic hybrid materials for arsenic adsorption : surface complexation and intraparticle diffusion

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Arsenic removal through adsorption is one of the most widely applied techniques for arsenic removal from drinking water. Among the numerous arsenic adsorbents that have been developed, organic-inorganic hybrid materials are promising candidates due to the merits of their high arsenic affinity of the selected inorganic portion and high designability and moldability of the organic portion. Currently, the most successful organic-inorganic hybrid adsorbents for arsenic removal are metal-infused ion exchange resins, but the adsorption capacities and adsorption rates are relatively lower compared with other adsorbents. The exploration of new organic-inorganic hybrid materials with high performance is necessary. It is also important to study and understand the arsenic adsorption performance of any newly developed organic-inorganic hybrid material under the context of practical applications for arsenic removal from water. The arsenic adsorption performance of an adsorbent can be evaluated through batch tests including adsorption isotherm, adsorption kinetics, and adsorption envelope tests, which reveal the maximum arsenic adsorption capacity, adsorption uptake rate, and adsorption performance under different pH conditions, respectively. Surface complexation models (SCM) can be developed to simulate the adsorption performance as a function of pH, arsenic concentrations, and ionic strength. And estimation of important adsorption parameters such as surface site density, and adsorption equilibrium constants are possible through the successful interpretation of adsorption data with SCM. While SCMs explain the adsorption reaction at equilibrium conditions, mass transfer models are powerful tools that can assist in interpreting the adsorption kinetics data, and estimate the diffusion coefficients. This study aims to develop and explore new high-performance organic-inorganic hybrid adsorbents for arsenic adsorption and evaluate the adsorption performance of the developed materials. The focuses of the study include: 1. developing an organic-inorganic hybrid adsorbent with rapid sorption kinetics for lower arsenic concentration applications, 2. exploring organic-inorganic hybrid adsorbents with very high adsorption capacity, and 3. developing a new high performance granulated organic-inorganic hybrid adsorbent. ...