Drinking water treatment produces large quantities of sludge which requires further treatment and costly disposal. Beneficial use of such a “waste” is of significance. We attempted to convert drinking water treatment sludge to sorbents for potential use for pollution control. A series of sorbent materials were produced by incineration at different temperatures over different durations, followed by treatment with strong acid. The yielding solids, along with the original sludge, were characterized for their surface structure properties. Compared to the original sludge, the sorbents have fluffier surfaces and doubled specific surface areas (36.7 m<sup>2</sup>/g) with smaller average pore size (78.3 Å). A preliminary adsorption test showed that the solid treated at 600 °C for 4 h followed by activation of 4 M HCl at a solid-to-acid ratio of 1:1 exhibit the highest affinity for Mo(VI). We thus used this solid as the sorbent for extensive adsorption study. Our results showed that the equilibrium adsorption data were fit well to the Langmuir isotherm model, with a maximum adsorption amount of 39.5 mg/g measured at 298 K and pH 4.0, compared to 18.4 mg/g measured at the same conditions for the original sludge. The rates of adsorption followed a pseudo-second-order rate model, and the adsorption process attained apparent equilibrium in less than 15h at same conditions. It is likely that the adsorption may follow electrostatic interaction and ion exchange mechanisms. Adsorption isotherms measured at different temperature conditions indicated that the adsorption process is endothermal. Further tests showed that the equilibrium adsorption was highly pH-dependent, with lower pH favoring Mo(VI) adsorption. Regeneration experiments revealed that the sorbent can be reused for removal of Mo(VI). The study suggested that sludge be converted to sorbent for treating wastewater containing such heavy metals as Mo(VI).

Adsorption of molybdenum(VI) on solids derived from sludge of water treatment processes

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.