Adsorption of p-cresol on Granular Activated Carbon

Abstract

Swine farming emit several odorous volatile organic compounds, one of which is p-cresol. Considering the layout of a swine barn, adsorption is one of the most suitable technologies for mitigating organic pollutants. In this study, commercial granular activated carbon (GAC) was tested as an adsorbent for removing p-cresol from aqueous solution. The objectives were to: 1) determine the combined effect of temperature, pH, and adsorbent dose on adsorption, (2) investigate the effect of volatile fatty acids and aldehydes on adsorption of p-cresol, (3) determine adsorption kinetics and isotherms, (4) study the effect of solvent on adsorption, (5) propose a possible mechanism of adsorption, and (6) discuss practical implications and design calculations for estimating adsorption of p-cresol on activated carbon. Batch experiments with GAC were performed to assess the combined effects of temperature (15-35 °C), pH (6-8), and adsorbent dose (10-30 g L^-1) on adsorption of p-cresol. The results indicated that adsorption capacity of p-cresol decreased with increasing adsorbent dose, whereas the effects of pH and temperature were not significant. Optimum adsorption capacity of 12.02 mg g^-1 was observed at temperature of 25 °C, pH of 7, and adsorbent dose of 0.32g. It was also found that presence of isovaleric acid and formaldehyde enhanced adsorption of p-cresol. Kinetic analyses indicated that p-cresol adsorbed mainly via chemisorption and adsorption was limited mainly via intra-particle diffusion. The role of solvent was not significant suggesting that water did not compete with p-cresol. Furthermore, surface oxygen somewhat inhibited adsorption of p-cresol perhaps due to enhancement of hydrophilicity. It is proposed that adsorption occurred mainly via electron-transfer between p-cresol and activated carbon. Sample design calculations are also presented to aid the swine producers to estimate the carbon dosage.