Agricultural bio-waste for removal of organic and inorganic contaminants from waste diesel engine oil.

Corncob, an agricultural bio-waste, was used as adsorbent to remove organic and inorganic contaminants in waste lubricating oil (WLO) from diesel engine. To improve its adsorption capacity, corncob was modified with mixed solution of nitric acid, Hexadecyl trimethyl ammonium bromide and ethanol. Characterization results showed the crystallinity index of corncob enhanced 12%, which would be ascribed to the disruption of the dense lignin-carbohydrates structure in lignocellulose biomass by modification. The surface of modified corncob became smoother and porous. The adsorption results showed modified corncob had better removal rates to contaminants than raw corncob. For WLO with 80,000 km mileage, the removal rates to Fe, Al, Cu were enhanced from 19%, 6.4%, 48-27%, 27%, 53%, while that for oxide, sulphate, aromates, soot and insoluble resins were enhanced 1.7, 1.2, 3.0, 1.7 and 1.7 times. The reduction rate of total acid number to WLO with 40,000, 60,000, 80,000 km were enhanced 16%, 9%, 12% by modified corncob, respectively. The optimal adsorption condition was explored as adsorbing 60 min at 90 °C with 2% adsorbent. Corncob, with the advantages of low cost, good biodegradability and high adsorption capacity, could be used as alternative to conventional adsorbent for WLO.

Natural adsorbent based on sawdust for removing impurities in waste lubricants.

Sawdust was expected to remove impurities in waste lubricant, and was modified with sodium hydroxide and triethanolamine, which can ameliorate its surface properties and improve its adsorption capacity. The increase of hydroxyl groups, the decrease of carbonyl groups and grafting new azyl after modification were beneficial for the adsorption of impurities. The surface area of modified sawdust is 0.969 m2 g-1, which is nearly 1.39 times as much as raw sawdust. The point of zero charge for modified sawdust decreased from 6.75 to 5.68 while the crystallinity of modified sawdust increased from 40.35 to 56.16. This research discovered that compared with raw sawdust and filter paper, modified sawdust possessed superior adsorption performances. The removal percentages for Si, Al, Fe, Cu was enhanced from 2.54%, 20.34%, 16.55%, 0.26% to 15.37%, 21.99%, 45.37%, 4.88%, respectively, while that for oxidation, aromatics, sulphation, soot and water was improved by 4.33, 4.69, 0.76, 1.20, 1.28 times at 80 °C with 1000 rpm for 12 h. The research has also explored the optimum adsorption conditions (adsorption temperature, adsorption time and rotation rate). The modified sawdust showed a stable adsorption capacity for impurities under different adsorption conditions.