A study on adsorption of anionic surfactant from water during riverbank filtration

Abstract

Riverbank filtration (RBF) is a low-cost and environmentally friendly alternative to advanced treatment technologies for pre-treatment or removal of various synthetic organic micro-pollutants from surface water. Through laboratory-scale batch tests employing aquifer soil with varying fine content and particle size, the removal of Linear Alkylbenzene Sulfonate (LAS) from river water during riverbank filtration (RBF) was investigated to determine its adsorption behavior. In addition to it, the effect of adsorbent dosage (3–60 g/L), adsorbate conc. (2–60 mg/L), contact time (10–240 min), agitation speed (80–200 rpm), and pH (2 to 10) on the adsorption for nine types of aquifer soil were studied in batch experiments. The optimal conditions for maximum rate of LAS adsorption on aquifer soil were found to be as initial LAS conc. of 15 mg/L, pH at 7, contact time of 150 min, agitation speed at 160 rpm and adsorbent dosage of 15 g/L respectively. The removal efficiency of LAS was obtained as 88.9% for aquifer soil with 15% fine content and 86.3% for fine sand at an adsorbent dose of 15 g/L, initial LAS conc. of 15 mg/l, neutral pH, agitation speed of 160 rpm, and contact time of 150 mins. Equilibrium data were fitted to Langmuir and Freundlich isotherms, and Langmuir isotherm (R2 = 0.99) was revealed to be the best fit of these models. From multiple linear regression, the LAS removal by soil samples was found to be strongly associated with all five geo-environmental factors (R2 = 0.91). So during the design of the RBF system, suitable contact time or travel time should be maintained in addition to the selection of proper aquifer site conditions for the RBF.