Adsorption of heavy metals from the waste waters by means of carbon aerogel

In our modern world, our ecosystem is rapidly polluted due to high population growth rate, industry and of course waste which are discharged to the environment unconsciously. One of the most important reasons of this pollution is solid wastes and waste waters which are being disposed of in the environment and contain heavy metals. Metallic pollutants, unlike organic pollutants, can not be decomposed by means of chemical and biological processes. One of the methods used to eliminate metallic pollutants from the waste waters is adsorption of the heavy metals.In this study, adsorption of cobalt ions by means of a carbon aerogel has been investigated. For this purpose, first of all a carbon aerogel has been produced in this research. Aerogels have been obtained by drying aquagels with CO2 under supercritical conditions which aquagels were obtained by using sol-gel method with various molar ratios of resorcinol / formaldehyde, resorcinol / water mixtures. Among these carbon aerogels which are produced by pyrolyzing the aerogels obtained at 950 °C, those samples who have maximum surface area (466 m2/g) have been used in adsorption study. X ray analysis was employed to examine surface characteristics of the carbon aerogels produced.In the adsorption of Co (II) ion on commercially available carbon in a batch system setup, effects of contact time, pH, adsorbent dose, temperature, initial concentrations on adsorption have been investigated. It was observed that chemical adsorption has taken place due to fact that adsorption increases with the increased temperature and that adsorption of Co (II) ion is in compliance with Langmuir isotherm.Three important variables which are influential on adsorption process, namely pH, adsorbent dose and temperature have been elected as independent variables with response-surface method approach. By using statistical quadratic multi-term equations, effects of the parameters have been maximized by using Box-Wilson experimental design method. In case maximum adsorption percentage for Co (II) has been determined to be 94,63%, adsorbent concentration, pH and temperature values have been determined to be 0,16 g absorbent /50 ml Cobalt (II), 9,92 and 68,1 °C respectively. In accordance with the results of the adsorption experiment carried out under optimum conditions with commercially available and our produced carbon gels, adsorption percentages have been determined to be 91,58 and 65,77% respectively.Desorption of cobalt ions which are retained on carbon aerogel particles remaining on the filter as a result of filtering from the solution of commercially available aerogels which are used in adsorption experiments under optimum conditions, was investigated by using 1 M /50 ml concentrations of H2SO4, EDTA, HCl and Na2CO3. It was determined that desorption rate is very low (7,09 ? 0,9). These results obtained, support the conclusion that adsorption of Co(II) ions on carbon aerogels is a result of chemical adsorption.