Performance of activated carbon/nanoscale zero-valent iron for removal of trihalomethanes (THMs) at infinitesimal concentration in drinking water

• The chlorination disinfection by-products water is from a local municipal water supply plant.
• The dispersion of modified nanoscale zero-valent iron (NZVI) was enhanced.
• The removal rate increased with the increase of bromine atoms in trihalomethanes (THMs).
• Change of pH during the process of removal of THMs was measured.
• The composites (NZVI/AC) were highly effective for low concentration THMs.

Trihalomethanes (THMs) in drinking water are difficult to remove with conventional methods. In this study, activated carbon supported nanoscale zero-valent iron (NZVI/AC) was synthesized by liquid-phase reduction and used to treat THMs in actual drinking water, including chloroform (CHCl3), bromodichloromethane (CHBrCl2), dibromochloromethane (CHBr2Cl) and bromoform (CHBr3). The as-prepared NZVI/AC composites were characterized in terms of specific surface area, pore size distribution, morphological properties and structural features. The effects of NZVI dosage, initial pH and contact time on removal efficiency were also studied. Scanning electron microscopy showed uniformly dispersed NZVI particles with diameters of 30–100 nm on average on the surface or inside the pores of AC. The removal efficiency was enhanced with the increasing amount of NZVI/AC, and the optimum dosage was 1.8 g/L and the optimal was 7. The kinetics of the removal of THMs was in agreement with a pseudo-first-order model. NZVI/AC accelerated removal rate of THMs over NZVI alone by both its higher reactivity and greater adsorption. The degradation products were analyzed using gas chromatography–mass spectrometry which showed that dehalogenation of THMs by NZVI/AC followed the order of CHBr3 > CHBr2Cl > CHBrCl2 > CHCl3. AC-supported nanoscale zero-valent iron particles is a promising sustainable material for potential application in elimination of THMs from actual drinking water.

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