Creation of an adsorbent from spent diatomaceous earth tailored to purify water from oil

It is known that spent diatomaceous earth (diatomite; kieselguhr), one of the main waste products from the beer filtration process, can be used as an adsorbent to purify water from crude oil. The thermal and chemical modification of this waste product increases its oil capacity. The conducted study was aimed at obtaining a sorbent tailored to purify water from oil using different modifications of spent diatomaceous earth. Preliminary studies revealed that the modification of spent diatomaceous earth is affected by the chemical nature and concentration of the modifying agent, as well as the temperature and duration of exposure. Alkaline modification of spent diatomaceous earth is more effective than acid modification; modification with sodium hydroxide solution produces the greatest effect on oil capacity. The maximum oil capacity is exhibited by spent diatomaceous earth modified with 1.5 M sodium hydroxide solution at 75 °С for 120 min. In order to optimize the procedure for obtaining an adsorbent suitable for purifying water from oil, a full factorial design was implemented on the basis of preliminary experimental data using Statistica 10.0, and additional experiments were conducted. An analysis of Pareto charts of standardized effects revealed that the modification process of spent diatomaceous earth is significantly affected by the modifying reagent concentration and the modification process temperature. Therefore, modification with 1.5 M sodium hydroxide solution at 75 °С for 30 min is the most optimal and effective procedure for obtaining an adsorbent suitable for purifying water from oil.