Groundwater arsenic removal using granular TiO2: integrated laboratory and field study

Area of Science:

• Environmental Science
• Water Treatment Technology
• Materials Science

Background:

• High arsenic concentrations in groundwater present a significant global health risk.
• Developing cost-effective and efficient arsenic removal technologies is crucial for public health, especially in geogenic areas.
• Granular titanium dioxide (GTiO2) shows potential as an adsorbent for arsenic remediation.

Purpose of the Study:

• To evaluate the efficacy of granular titanium dioxide (GTiO2) for removing arsenic (As) from groundwater.
• To investigate the adsorption kinetics, isotherms, and the influence of common ions on arsenic removal by GTiO2.
• To assess the long-term performance of GTiO2 in household water filters under realistic conditions.

Main Methods:

• Adsorption experiments were conducted to determine kinetics (Weber-Morris model) and isotherms (Langmuir model).
• The impact of various ions (Ca2+, Mg2+, silicate, HCO3-) on arsenic adsorption was systematically studied.
• Field column tests were performed to evaluate performance at different empty bed contact times (EBCTs), followed by modeling using PHREEQC with the CD-MUSIC model.

Main Results:

• GTiO2 exhibited high adsorption capacities for As(III) (106.4 mg/g) and As(V) (38.3 mg/g).
• Cations like Ca2+ and Mg2+ enhanced As(V) adsorption, while silicate and bicarbonate significantly inhibited the removal of both As(III) and As(V).
• Column tests showed effective removal of ~700 μg/L As for 968 bed volumes, and household filters provided safe water for extended periods (288-600 days).

Conclusions:

• Granular titanium dioxide is a highly effective adsorbent for removing arsenic from contaminated groundwater.
• Understanding the influence of water matrix ions is critical for optimizing arsenic removal systems.
• The study provides a validated approach for designing practical, long-term arsenic removal solutions for household use.