Kinetic Curves of Sorption of Petroleum Products by Calcined Sorbent from Ash-and-Slag Waste of Thermal Power Engineering

Experimental studies of the dynamic sorption of model mixtures containing petroleum products are carried out. Dried and calcined ash-and-slag waste accumulated by the method of hydraulic ash removal at the ash dump of Novocherkassk State District Power Plant (Novocherkassk, Rostov Region, Russia) are studied as a sorbent. The weight of the calcined sorbent for each model solution is fixed and amounts to 5.0 g. The model solutions are passed through a column filled with calcined sorbent. At the first stage, experimental studies are conducted to optimize the filtrate flow rate in the range from 0.05 to 2.5 L/min with a step of 0.05 L/min. Model aqueous solutions with a hydrogen index of pH 7.5, containing 100 mg/L of petroleum products, are passed through a column containing 5 g of calcined sorbent. The optimal filtrate flow rate is 0.1 L/min with a maximum efficiency of extraction of petroleum products from the solution of 84%. At the second stage, the kinetic dependences of the sorption capacity and concentration of petroleum products in the filtrate are constructed. For this purpose, experimental studies are conducted on the saturation of the sorbent with petroleum products by means of passing a model aqueous solution containing 10 000 mg/L in portions of 0.05 L through a column filled with calcined sorbent in the amount of 5 g, with the filtrate collection rate of 0.1 L/min. The maximum value of sorption capacity was 560 mg/g with an extraction efficiency of petroleum products from the solution of 85%. Based on the analysis of the results of experimental studies, an approach to the mathematical description of the kinetics of the sorption of petroleum products is proposed. The calculation of the concentration of petroleum products in the filtrate is divided into two stages. At the first stage, the increase in the concentration of petroleum products in the filtrate occurs when the sorbent is saturated with petroleum products at less than the maximum value of the sorption capacity; the second stage occurs after the maximum value of the sorption capacity is reached. Kinetic equations are given for calculating the sorption capacity and concentration of petroleum products in the filtrate. Good qualitative agreement between the experimental and calculated data is obtained.