Synthesis of carbon aerogels and use in adsorption of heavy metals

As it is known, the presence of heavy metals in wastewater causes serious environmental problems. One of the disposal methods of these wastes is adsorption. The use of carbon aerogels as an adsorbent in the removal of heavy metals has been a popular research topic due to their highly porous structure and surface area, low density. The production method of carbon aerogels affects the obtaining of different morphologies/shapes in the pore size distributions. In this study, carbon aerogel adsorbents were synthesized for the treatment of heavy metal-containing wastewater by adsorption and their adsorption properties were determined. Carbon aerogels were prepared using a sol-gel process involving polycondensation of resorcinol and formaldehyde at different catalyst ratios with two different catalysts (Mg(OH)2 and Na2CO3). The produced aerogels were dried by the ambient pressure drying method, which is a simpler, less costly, industrially applicable drying method, and then carbon aerogels were produced by subjecting the obtained aerogels to carbonization. The morphological properties of the synthesized carbon aerogels were characterized by SEM, TEM and XRD analyzes and their chemical structures were characterized using FTIR and Raman spectroscopy. The removal of these heavy metal ions from solutions containing Cr(VI) and Cu(II) ions was studied using synthesized carbon aerogels. The data obtained as a result of the experiments were analyzed with the Langmuir and Freundlich isotherm equations. The maximum adsorption capacity for Cr(VI) according to the Langmuir isotherm was approximately equal to around 154 mg/g for carbon aerogels prepared with both catalysts. While the highest adsorption capacities of Cu(II) were 112.35 mg/g for carbon aerogel synthesized with Mg(OH)2 catalyst, it was determined as 79.94 mg/g for carbon aerogel synthesized with Na2CO3 catalyst. Considering the kinetic studies, it was determined that the adsorption took place in accordance with the pseudo- second-order kinetic model. It was observed that different catalyst ratios did not affect the adsorption capacity of the synthesized aerogels much, as a result, it was determined that all the synthesized aerogels provided higher adsorption capacity for Cr(VI) adsorption than Cu(II) adsorption.