A B S T R A C TIn this study, coal-based granular activated carbon loaded with MnO 2 (ACLM) was tested as adsorbent for the removal of formaldehyde from aqueous solution. The ACLM was characterized by scanning electron microscopy, energy dispersive X-ray spectrometry, Brunauer-Emmett-Teller, and Fourier transform infrared spectra. The optimized pH of formaldehyde adsorption was 7.0. The removal percentage increased from 21.8 to 72.1% by raising the ACLM dosage from 0.1 to 1.0 g. The formaldehyde adsorption rate increased a little at initial formaldehyde concentrations from 0.6 to 1.8 mg/L. The adsorption equilibrium time was 24 h. The adsorption rate of formaldehyde increased from 58.1 to 61.2% with temperature rising from 298 to 308 K and decreased from 61.2 to 54.0% when temperature from 308 to 318 K. Isotherm modeling revealed that Langmuir equation could better describe the adsorption of formaldehyde onto the ACLM and the maximum adsorption capacity obtained was 4.53 mg/g. Kinetic data efficiently fitted with the pseudo-second order. The decrease of ΔG˚from 298 to 308 K suggested more favorable of formaldehyde adsorption onto the ACLM and increase of ΔG˚from 308 to 318 K revealed that the sorption was more unfavorable. Results from this study suggest that ACLM is an effective adsorbent for the removal of formaldehyde from aqueous solution in drinking water treatment field.

This study compared start-up and steady-state affecting factors of attapulgite composite ceramsite/quartz sand double-layer biofilter (ACC/QSDLBF) and quartz sand single-layer biofilter (QSSLBF) on micropolluted drinking source water treatment. Results showed that the ACC has suitable pore size distribution in the range of 5-850 nm which is conducive to biofiltration. Turbidity removal efficiency of ACC/QSDLBF was a little lower than QSSLBF, but organic matters and ammonia removal efficiencies of ACC/QSDLBF were much higher than QSSLBF due to biodegradation and nitrification by microorganisms colonizing on the ACC. At stable state, the growth of head loss for ACC/QSDLBF was lower than that of QSSLBF. The complete filtration cycle of ACC/ QSDLBF was 52 h. The total COD Mn removal rate of ACC/QSDLBF was 20.93 %, in which 90 % of removed total COD Mn was achieved at the upper 60 cm of ACC filter layer. The removal of COD Mn decreased from 35.89 to 13.16 % in ACC/QSDLBF when increasing hydraulic loading from 2 to 16 m/h. After analysis of efficient EBCT in ACC/QSDLBF, optimized hydraulic loading was 12 m/ h. These conclusions would be helpful to practical application of ACC as functional material for new construction of waterworks, especially upgrading of existing waterworks treating micropolluted drinking source water.