Arsenic Adsorption On Xerogel, Aerogel, and Nanogel Activated Alumina

Various forms of sol-gel activated alumina (AA) have been synthetized and tested as potential arsenic adsorbent materials. Some of them included xerogel, aerogel and Nanogel AA. Synthesis of the sol-gel was made following the Yoldas method which included hydrolysis, peptization, gelation and calcination.  In the present study, modifications to the Yoldas method to produce aerogel and Nanogel AA included using supercritical-CO₂ extraction and addition of nanoparticles, respectively.  Equilibrium experiments were conducted to determine optimum pH conditions for adsorption and maximum adsorption capacity. Results were compared with two commercial activated alumina adsorbent materials, namely H-156 and Axens.  It has been observed that Xerogel removed arsenic at any pH within the range of 2.0 and 10.0. It has also been observed that the tendency to increase arsenic uptake for the synthesized adsorbents increased in the order or Xerogel AA > Axens > Aerogel AA > H-156 AA > Nanogel AA. The adsorption capacity of Xerogel can be modeled following the Freundlich adsoption isotherm. The pH independency and superior adsorption capacity for Xerogel AA makes this material a feasible and economic alternative for arsenic removal from drinking water without the need of adding buffer chemicals for pH adjustment.