Hydrocarbons removal from underground coal gasification water by organic adsorbents

The main problems in the case of the undergorund coal gasificiation process is the possible pollution of surrounding aquifers. The underground gasification cavity is a source of both gaseous and liquid pollutants and these are mainly aromatic hydrocarbons, phenols, heavy metals and others. In order to prevent underground water from pollution a permeable reactive barrier was proposed. The filling was granulated activated carbon and SPILL-SORB (peat) - two commonly available sorbents adequate for hydrocarbons removal. The wastewater (synthetic solution which simulated groundwater contaminated with the UCG products) was prepared by mixing distilled water with desired amounts of substances such as phenols, benzene, toluene, xylene, naphthalene etc. Batch tests were performed in order to measure sorption of phenols and benzene from the post-UCG water on the mentioned sorbents. Experimental results were fitted with linear and non-linear Freundlich and Langmuir isotherm models. The obtained data showed that removal of phenols and benzene in case of GAC was much more efficient. However, sorption was lower than in the case of literature data and can be explained by complex composition of the solution and pre-treatment of the samples. The Langmuir model gave a better fit in the case of GAC, whereas Freundlich isotherm model was matching the data better in case of SPILL-SORB.