Investigation of the adsorption of heterocyclic aromatic compounds onto natural clays

In this research, the removal of four heterocyclic compounds, which are known as pollutants for the environment and cancerogenic, from aqueous solutions by using the adsorption method was investigated. Natural bentonite, natural sepiolite and organo-clays obtained by the modification of these natural clays by some of the surfactants were used as adsorbents and suitable adsorbents were determined for each compound. The maximum adsorption amounts were obtained with natural bentonite for quinoline (Q), 8-hydroxyquinoline (8HQ) and benzothiophene (BT), and with natural bentonite modified with hexadecyltrimethylammonium (HDTMA) bromide (HDTMA-bentonite) HDTMA-bentonite for dibenzofuran (DBF). The adsorption of Q, 8HQ and BT onto natural bentonite and DBF onto was investigated by means of pH, time and temperature and adsorption kinetic, isotherm and thermodynamic parameters were calculated by using experimental data. Lagergren-first-order, pseudo-second-order and intraparticular diffusion kinetic models and Langmuir and Freundlich isotherm models were applied to the experimental data to obtain adsorption kinetics and adsorption equilibrium. The activation energy, the changes in free energy, enthalpy and entropy were determined. The desorption studies were carried out to have an information about the reusability of the adsorbents. The characterization studies were also done by using FTIR, XRD, BET, TG and elemental analysis to identify the adsorption processes and the modification of natural bentonite with HDTMA.