Separation of formic acid and acetic acid from aqueous solutions using sugar beet processing fly ash: characterization, kinetics, isotherms and thermodynamics

Abstract

The present study is on the use of sugar beet processing fly ash (SPFA) during the separation of acetic acid (AA) and formic acid (FA) from aqueous solutions by adsorption technique. Kinetic studies showed that the equilibration time was about 70 min for AA while 60 min for FA. The related data were observed to follow the pseudo-second-order kinetic model. Isotherm curves exhibited that the process was fitted with Type 1. The adsorption efficiency increased with the increase in SPFA dosage and decreased with the AA or FA concentration. Equilibrium data were in consistency with the Langmuir isotherm model for both solutes. The adsorption capacities and removal efficiencies obtained with FA were higher than those with AA. The maximum values were 7.00 and 5.60 mmol/g for FA and AA, respectively. These values were considerably higher than the ones previously reported for the adsorption of these acids using several types of synthetic resins and fly ashes. Temperature negatively influenced the process but the effect was not significant. Regardless of the acid type studied, the process was exothermic and spontaneous. The results showed that SPFA can be efficiently used in the separation of these carboxylic acids from aqueous solutions.