Comparative empirical evaluation of the aqueous adsorptive sequestration potential of low-cost feldspar-biochar composites for ivermectin

Several recent studies are shedding light on the potential of synergistically combined low-cost adsorbents for organic and inorganic contaminants removal in water treatment. However, there exists a dearth of data for their potential for removal of emerging contaminants. In this study, low-cost feldspar (FLC) was combined with blended Carica papaya or pine cone seeds (ratio of 1:1), and calcined to obtain FLC-Carica papaya seeds (FPA) or FLC-pine cone seeds (FPC) composites which were characterized. The composites were evaluated for ivermectin sorption by varying experimental pH, time, concentration and temperature, as well as their potential for reusability. The FLC structural lattice was not significantly affected by the modification process but the composites exhibited physicochemical features which were markedly different, having new FTIR spectra bands, well reduced surface area, and enhanced cation exchange capacity. The composites ivermectin sorption rates and equilibrium were faster (60 min) than the FLC (360 min). Ivermectin sorption was pH and concentration dependent. The sorption data fitted better to the homogeneous fractal pseudo-second order (FPSO) kinetics and Freundlich adsorption isotherm model; implying that the process involves complex sorption mechanism. The process was exothermic and increase in solution temperature up to 39.5 degrees C did not enhance sorption. Ivermectin sorption capacity and rate trends were similar: FPA (110.9 mu g/g) >FLC (84.6 mu g/g) >FPC (62.7 mu g/g). The FPA exhibited the best sorption capacity as well as the best reusability with over 64% of its initial sorption capacity retained on first reuse. The FPA also exhibited high potential to reduce ivermectin in low concentration solution (approximate to 75 mu g/L) to zero, with the trend of FPA <= FLC (5.0 +/- 1.5 mu g/L) >FPC (approximate to 27.5 mu g/L). Though this kind of composite possesses economic potential in water treatment applications, not every biochar modification may result in enhanced sorption process.