Characterization and modification of porous ceramic sorbent for arsenate removal

Porous ceramic sorbent, synthesized with a mixture of akadama mud, wheat starch, and Fe2O3, has been used for the removal of arsenic, which is an extremely toxic contaminant even at very low concentrations. Acid washing process using dilute HCl solvent and iron impregnation using ferric and ferrous solutions were applied to modify the ceramic for enhancing arsenic removal performance. The batch results indicated that ferric impregnated ceramic (ceramic/FeCl3) exhibited the best arsenic adsorption efficiency at room temperature (25 °C) under neutral conditions (pH 6.9). And its maximum adsorption capacity for arsenic removal was 7.12 mg/g, estimated by the Langmuir–Freundlich equation with correlation coefficient of 0.984. The equilibrium data also well fitted to Dubinin–Radushkevich adsorption isotherms with a sorption energy E = 8.11 kJ/mol, indicating that the mechanism for As(V) adsorption on ceramic/FeCl3 was a combination of chemical ion exchange and physical electrostatic attraction, in which chemisorption seemed to be a little stronger. No secondary pollution (toxic sludge and leached iron) caused by the ceramic/FeCl3 was observed.

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► Porous ceramic adsorbent was synthesized and modified for As removal.
► The FeCl3 modified ceramic sorbent showed best As removal performance.
► Fe3+ impregnation has a combination force of the acidification and iron precipitation.
► Such two effects result in a large surface area and Fe–As surface exchanger.
► Ceramic sorbents can be separated from water simply, and no toxic sludge or leached iron was observed.