TiO2-coated natural zeolite: Rapid humic acid adsorption and effective photocatalytic regeneration

• Coating TiO2 onto zeolite markedly improve its efficiency in adsorbing HA.
• Most of the bulk organic (up to 80%) can be removed within 5 min of adsorption.
• Immobilisation of TiO2 onto zeolite permits easier separation of the adsorbent.
• Zeolite/TiO2 particles were readily regenerated by UVA irradiation.
• After regeneration, the adsorbent can be reused repeatedly.

Natural zeolite coated with titanium dioxide (TiO2) was used as an adsorbent to rapidly remove humic acid (HA) from an aqueous solution. Coating TiO2 onto zeolite markedly improved its efficiency in adsorbing HA: most of the bulk organic matter (80%) could be removed within 5 min of adsorption by the zeolite/TiO2 particles at neutral pH, whereas less than 20% was removed by bare zeolite alone. In addition, immobilisation of TiO2 onto zeolite permitted easier separation of the adsorbent from the treated water. Photocatalytic properties of TiO2 were exploited for the regeneration of the adsorbent. The adsorbent was shown to be readily regenerated by photocatalytic oxidation and was still effective in removing HA after 5 adsorption/regeneration cycles. These results indicate that TiO2-coated zeolite can be a very attractive adsorbent for the rapid removal of HA from aqueous solutions.