Optimization of extractive removal of formic acid from water by tri-n-propyl amine and dibenzyl amine in mono and dibasic ester diluents: LSER modelling

Abstract

A comparative study of reactive extraction of formic acid from water by tri-n-propyl amine (TPA) and dibenzyl amine (DBA) dissolved in ester and alcohol diluents has been carried out at T = 298.2 K and P = 101.3 kPa. The uptake capacity of the amine/diluent system is ranging in the order, isoamyl alcohol > diethyl malonate > diethyl succinate > diethyl sebacate > ethyl valerate > ethyl caprylate, and TPA > DBA. Different mechanisms control favourably monotype (1: 1 or 1: 2) and two types (1: 2 and 1: 3, or 1: 1 and 1: 3) formic acid-amine aggregation in the organic phase depending on the solvation efficiency of diluent. Monobasic esters are more effective solvating agents for organic complexes, whereas amine/isoamyl alcohol mixture yields larger extraction factors of D > 1, Z(t) > 1, and E > 50% due to the simultaneous effect of physical extraction and chemical interaction. An optimization structure has been formulated for efficiently identifying the optimum ranges of separation ratio R and synergistic enhancement SE factors based on the derivative variation method. The most compatible optimization ranges for the extractive recovery of formic acid from water are 1 < R < 8 and 5 < SE < 10. The correlative performance of LSER and mass action law models has shown considerable success. The deviation statistics testify the ability of LSER to simulate accurately the observed properties with a mean error of 4.7%.