Optimization of feed and extractant concentration for the liquid-liquid extraction of volatile fatty acids from synthetic solution and landfill leachate

Liquid-liquid extraction of volatile fatty acids (VFA) from landfill leachate (LL) as well as synthetic solution (SS) whose concentration varied from 0.2 – 1 mol/L was investigated. The impact of extractant and feed VFA concentration on extraction efficiency (EE), distribution ratio (KD) and loading ratio (z) with the help of statistical analysis and process optimization using response surface methodology is presented. Physical extraction of VFA from SS using seven different diluents was performed to choose the best diluent. Reactive extraction of VFA was investigated with 10 % - 50 % (v/v) trioctylamine (TOA) and tributylphosphate (TBP) as extractants in 1-Octanol. Reactive extraction of VFA results disclosed enhancement of EE due to the synergistic chemical interactions between extractant and diluent. Majority of the acid extractant complexes formed were 1:1 with TBP while 1:1, 2:1 and 3:1 with TOA as verified by z > 0.5 The optimal extractant concentration for TOA and TBP was found to be 37.8 % and 39.09 % at a feed concentration of 0.67 mol/L and 0.81 mol/L for SS respectively to achieve maximum EE of 91 % while it was 29.3 % and 36.2 % at 0.2 mol/L for LL to achieve EE of 52 % and 57 % correspondingly.