Adsorption of organic acids on activated carbon in column

Adsorpcija je sposobnost površine krutih tvari da na sebe veže čestice plinova ili otopljenih tvari. Ta pojava je od vrlo velike koristi u separacijskim procesima, posebice za uklanjanje industrijskih onečišćenja poput teških metala, farmaceutika, bojila i organskih kiselina iz otpadnih voda. U ovom radu ispitivana je adsorpcija organskih kiselina, octene (CH3COOH) i mravlje (HCOOH). Ispitivanje je provedeno u kolonskom sustavu s fiksnim slojem granuliranog aktivnog ugljena (GAC) visine 10 cm pri stalnoj brzini protoka od 21,9 ± 3,3 mL min^-1. Prvo su preko modela Freundlich-ove izoterme opisane adsorpcijske ravnoteže zadanih kiselina koje su pokazale vrlo blizak afinitet za adsorpciju. Rezultati mjerenja su prikazani krivuljama proboja koje nam opisuju omjer izlazne i ulazne koncentracije otopine (c/c0) u ovisnosti o volumenu propuštene otopine. Usporedbom krivulja proboja različitih koncentracija iste kiseline ili istih koncentracija različitih kiselina se procijenio utjecaj koncentracije i oblika molekule na brzinu adsorpcije. Vidljivo je da porastom koncentracije raste brzina adsorpcije, a pri nižim koncentracijama (c < 4 mol L^-1) je vidljiv utjecaj oblika molekule pri čemu se veća molekula (octena kiselina) brže adsorbira. Pri višoj koncentraciji je utjecaj oblika molekule zanemariv u odnosu na utjecaj koncentracije.Adsorption is the surface ability of solid mater to bond with particles of gases or dissolved matter. This phenomenon is of great use in many separation processes, especially in the removal of industrial pollutants like heavy metals, pharmaceuticals, dyes and organic acids from wastewaters. This paper studies the adsorption of organic acids, acetic (CH3COOH) and formic (HCOOH). The study was performed in a column system with a fixed bed of granulated active carbon (GAC) with the height of 10 cm, and with a continuous flow of 21,9 ± 3,3 mL min^-1. First, the adsorption equilibrium of given acids was determined by the Freundlich isotherm model. Both acids showed similar affinity for adsorption. The results were shown by plotting the breakthrough curves that show the dependence of c/c0 to V/mL where c/c0 is the ratio of the solutions concentration before and after adsorption, and V/mL is the volume of the solution that passed through the column. The effect of concentration and particle shape was determined by comparing the breakthrough curves for the solution of the same acid with different concentrations, and by comparing both acids to each other at the same concentrations. The results showed that the speed of adsorption rises with the rise of concentration. At lower concentrations (c < 4 mol L^-1) the effect of molecular shape is also shown as acetic acid is adsorbed in less time than formic acid of the same concentration. At higher concentrations the effect of molecular shape is negligible compared to the effect of concentration