Novel water-purification hybrid processes involving in-situ regenerated activated carbon, membrane separation and advanced oxidation

The reported pilot-scale development of hybrid process alternatives, combines in-situ regenerated powdered activated carbon (PAC), H2O2-based advanced oxidation techniques and membrane ultrafiltration (UF). Commercial PAC and special iron-impregnated PAC (PAC-Fe) were used as adsorbents, whereas diclofenac (DCF), a commonly detected pharmaceutical in water-sources, was employed as representative micro-pollutant. For PAC regeneration, modest on-line H2O2 dosage was adopted, alone or in combination with UV-C irradiation. Large DCF uptake was measured for both PAC (154.5 mg/g) and PAC-Fe (116.7 mg/g), while the regeneration efficiencies achieved with the photo-assisted H2O2 processes were much greater (122.2% and 131.6% for H2O2+UVC and photo-Fenton, respectively) than those obtained with H2O2 alone (70% and 77.6% for H2O2 and Fenton, respectively). For PAC-Fe, enhanced recovery of adsorption capacity suggests occurrence of heterogeneous Fenton-like reactions on iron-oxide particle surfaces leading to generation of OH and other reactive species by H2O2-decomposition. The catalytic adsorbent (PAC-Fe) retained its stability and activity after three operating cycles, which would significantly reduce operating cost in practical applications. Considering the rather short regeneration-time of present tests (180 min) and the nearly basic pH of feed solutions, the novel processes investigated herein, involving PAC regeneration in the same equipment employed for water purification, hold distinct advantages over conventional methods.