Adsorption of polynuclear aromatic hydrocarbons from aqueous solution:  Agrowaste-modified kaolinite vs surfactant modified bentonite

R. A. Düring,L. Böhm,B. I. Olu-Owolabi,E. I. Unuabonah

doi:10.4314/bcse.v30i3.5

Abstract

. The adsorption efficiency of a new hybrid clay adsorbent for polynuclear aromatic hydrocarbons (PAHs) is compared with known modified clay adsorbents. The new hybrid clay adsorbent (HYCA) showed far higher adsorption capacities for the adsorption of various PAH molecules compared with sodium dodecyl sulfate modified and humic acid modified Bentonite clay adsorbents. With the new hybrid clay adsorbent (HYCA), the adsorption of some of the larger PAH molecules was complete in the first 1 h as compared with ≈ 62% and ≈ 76% observed for both humic acid modified and sodium dodecyl sulfate modified Bentonite clay adsorbents respectively. In 24 h adsorption of the PAHs was complete for all adsorbents with HYCA adsorbent showing better efficiency in the removal of the PAH molecules from aqueous solutions. No significant change was observed with increase in time up to 48 h. The adsorption was observed to be more spontaneous with HYCA adsorbent than with either modified Bentonite adsorbents. The enthalpy of adsorption did not follow any specific order and were not consistent for all PAH molecules considered. KEY WORDS: Adsorption, Polynuclear aromatic hydrocarbons, Enthalpy, Hybrid clay, Bentonite Bull. Chem. Soc. Ethiop. 2016, 30(3), 369-376DOI: http://dx.doi.org/10.4314/bcse.v30i3.5

Highlights

Polynuclear aromatic hydrocarbons (PAHs) are persistent toxic pollutants consisting of two or more fused benzene rings
This study presents a new hybrid clay adsorbent which is a composite of both Bentonite clay and an agricultural waste (Carica papaya seeds)
With sodium dodecyl sulfate modified Bentonite, adsorption capacity increased with increasing molecular weight of the various PAHs while the reverse was observed for HB

Summary

Introduction

Polynuclear aromatic hydrocarbons (PAHs) are persistent toxic pollutants consisting of two or more fused benzene rings. With sodium dodecyl sulfate modified Bentonite, adsorption capacity increased with increasing molecular weight of the various PAHs while the reverse was observed for HB. The adsorption capacities of HB for the higher PAHs decreased as a result of the hydrophilic nature introduced by the humic acid on the Bentonite surface.

Results

Conclusion