Sorptive removal of ibuprofen from water using selected soil minerals and activated carbon

Pharmaceuticals have gained significant attention in recent years due to the environmental risks posed by their versatile application and occurrence in the natural aquatic environment. The transportation and distribution of pharmaceuticals in the environmental media mainly depends on their sorption behavior in soils, sediment–water systems and waste water treatment plants, which varies widely across pharmaceuticals. Sorption of ibuprofen, a non-steroidal anti-inflammatory drug, onto various soil minerals, viz., kaolinite, montmorillonite, goethite, and activated carbon, as a function of pH (3–11), ionic strength (NaCl concentration: 0.001–0.5 M), and the humic acid concentration (0–1,000 mg/L) was investigated through batch experiments. Experimental results showed that the sorption of ibuprofen onto all sorbents was highest at pH 3, with highest sorption capacity for activated carbon (28.5 mg/g). Among the minerals, montmorillonite sorbed more ibuprofen than kaolinite and goethite, with sorption capacity increasing in the order goethite (2.2 mg/g) < kaolinite (3.1 mg/g) < montmorillonite (6.1 mg/g). The sorption capacity of the selected minerals increased with increase in ionic strength of the solution in acidic pH condition indicating that the effect of pH was predominant compared to that of ionic strength. An increase in humic acid concentration from low to high values made the sorption phenomena very complex in the soil minerals. Based on the experimental observations, montmorillonite, among the selected soil minerals, could serve as a good candidate to remove high concentrations of ibuprofen from aqueous solution.

Keywords
Goethite; Kaolinite; Montmorillonite; Natural organic matter; Pharmaceuticals; Point of zero charge; Sorption