Studying the Mechanism of Using Grain Husks to Remove Dissolved Petrochemicals from Test Water

This paper presents our research on removing dissolved petrochemicals from water by sorption using vegetable matters. For this purpose, we used grain crop husks and their modifications as sorbents. We prepared test solutions and experimented on sorption in static and dynamic conditions. Grain husks were modified chemically and thermally. The experiments showed that modifying with 1% sulfuric acid (SA) solution and heating allow increasing the adsorption capacity by 10-15 % and 35-40 %, respectively. Dependencies obtained for the adsorption capacity of original and modified samples indicate that the isotherm of adsorbing the dissolved petrochemicals by grain husks is described by the Freundlich equation, which is evidence of a mixed-diffusion sorption mode. To identify the filter bed operation time, we measured the dynamic exchange capacity of five filter bed samples. According to various combinations of modified samples proposed as filter bed, heat-treated oat husks : acid-modified oat husks : heat-treated oat husks at a ratio of 4:6:4 at a water flow rate of 10-15 cm3 /min allows maintaining the filter operability of up to 6 hours. Oil gets adsorbed at WGH in the mixed-diffusion mode, while the internal diffusion is a stage that limits adsorption according to the activation energy estimates (6-20 kJ/mol). This is due to the structural features of cellulose and lignin contained in sorption materials (SM) that have a complex amorphous crystalline structure. Presumably, petrochemicals (PC) are adsorbed on the surface of SMs at the beginning of adsorption process, forming a monomolecular layer, and then, with increase in concentration, start penetrating into internal pores and filling out the amorphous crystalline zones in the composite structure