No abstract

The performance of ordinary and organophilic clays in the solidification and stabilization process was investigated with respect to the unconfined compressive strength (UCS) and leaching of phenol‐contaminated soil. The samples contained 2,000 mg/kg of phenol. White cement (15 and 30 percent by weight [wt%]) was used as binder, while ordinary and organophilic clays (8, 15, and 30 wt%) were applied as additives for reducing the harmful effects of phenol interference in cement hydration with a 28‐day curing time. The results revealed that the UCS is reduced by increasing the amount of clays. The values of UCS of all samples met the minimum standards specified for disposal in sanitary landfills determined by developed countries. The leaching test demonstrated that the degree of leaching diminished with increased clay content in all samples of both clay types. This reduction was observed to be greater in samples containing organophilic clay than in bentonite clay samples. Furthermore, the best composition of the materials tested was determined to be 30 wt% white cement plus 13.3 wt% organophilic clay with a compressive strength of 3,839 kPa, phenol removal percentage of 80 percent, and a cost of $67 per ton of contaminated soil.

In this research, wastes of used oil treatment plants have been studied for their pollution potential and geotechnical characteristics. A random sampling plan was used to collect 11 samples from the dump site. Moreover, statistical analysis indicated that six samples were required to prepare a representative sample for the wastes. Thus, a mixed sample was prepared to determine moisture content, pH, Atterberg limits and density of the waste. The analysis of organic compounds and heavy metals showed the presence of total petroleum hydrocarbons (TPH) and Barium as the main pollutants. The results also showed waste as a fine-grained soil heavily contaminated by petroleum hydrocarbons. The mean concentration of TPH was more than 216 g/kg, which is 832, 108 and 433 times greater than the acceptable cleanup levels for diesel range organics, oil range organics and TPH, respectively. Nevertheless, heavy metals concentrations are lower than proposed cleanup levels for industrial area. The moisture content, pH, liquid limit, plastic limit, plastic index and density of the mixed sample were 12. 26%, 9.6, 25.91, 15.83, 10.08 and 1.22 g/cm 3 , respectively. After that, several remediation techniques were evaluated to propose the best one based on the physical and chemical properties of the waste, the applicability of the method and implementation costs. Finally, solidification/stabilization technique using organophilic clay as the stabilizer, incineration and bioremediation techniques was recommended for cleanup of the site.

BACKGROUND: This research investigated the solidification/stabilization process (S/S) efficiency of contaminated soil by total petroleum hydrocarbons (TPH) in the waste of a used oil treatment plant using quick lime (QL) as a binder and modified clay (MC) as an additive. Several objectives were considered, including reducing the mobility and leaching of TPH, investigating the effect of MC on the QL hydration process in the presence of organic matter, the possibility of S/S waste reuse, and estimating the S/S cost for the optimum mixture. RESULTS:The unconfined compressive strength (UCS) increased about 45% by increasing 25% of QL without MC, but these S/S wastes did not satisfy the waste reuse standards. Additionally, adding any ratio of MC to samples containing QL increased UCS significantly. The UCS of all samples at the age of 28 days with different QL and MC proportions obtained more than 350 kPa (the minimum UCS required for S/S waste disposal in the landfill). Moreover, the toxicity characteristic leaching procedure (TCLP) test revealed that TPH leaching of contaminated soil was 3.8 mg L −1 but adding only 15% of QL could reduce TPH leaching to less than 1 mg L −1 , which is the maximum allowable TPH leaching.CONCLUSION: The combination of QL and MC decreased TPH leaching, significantly. The scanning electron microscopy analysis also showed that QL hydration was improved by increasing the amount of MC. Finally, a sample with 35% QL and 15% MC was selected as an optimum sample due to its cost of $80.5/ton.

No abstract