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Case Studies & Tests

Adsorption Lab Studies with Organoclay

Laboratory Studies of ET-1 Activated Clay

Adsorption of Acetone
Adsorption of Benzene
Adsorption of Pesticides
Toxicity of ET-1 and Crude Oil
Desorption / TCLP Testing
Efficacy of Hydrocarbon Adsorption by Organoclay

Adsorption of Acetone

We investigated the adsorption of 50 ppm acetone in water in 1995. 1700 milliliters of solution were placed in a sealed container with 500 grams of organoclay and agitated for 8 hours. 100 ml of filtrant were removed for analysis and the remaining solution was filtered again. The process was repeated two more times. Acetone concentrations were found as follows:

Initial concentration:       54 mg/L
Filtrant #1:                    27 mg/L
Filtrant #2:                    20 mg/L
Filtrant #3:                    12 mg/L

These results confirm the conclusions reached by the cited authors. First, we confirmed that organoclays made from high molecular weight QACs find it difficult to remove highly soluble organic molecules. Second, it opened up the possibility that this difficulty could be overcome by offering additional contact time with the media.

Adsorption of Benzene

Laboratory studies were conducted in 1996 to quantify the adsorption of benzene by ET-1. IT was discovered that ET-1 reaches equilibrium with water and benzene within approximately 60 seconds from initial contact. He further measured the adsorption behavior for ET-1 and benzene and constructed an adsorption isotherm. ET-1 exhibited a nearly constant loading of 680 mg benzene per gram ET-1, or 68% by weight from concentrations above 2%. This data is substantially better than that reported in the previous references.

Adsorption of Pesticides

We also conducted several treatability studies in 1996 on pesticide contaminated water. The studies were designed to replicate a commercial treatment package containing organoclay followed by activated carbon. In the first trial, 25 ppm lindane was treated with ET-1 only. In the second, charcoal replaced the ET-1. In the third, both media were placed in series, according to our recommended practices. Results were:

Influent Concentration                                     25 mg/L
Treated with ET-1 only (avg. of 4)                     0.010 mg/L
Treated with GAC only (avg. of 4)                     0.017 mg/L
Treated with ET-1 + GAC (avg. of 3)                 0.003 mg/L

Other pesticides including dursban, methoxyclor, transpermethrin, and cis-permethrin were also subjects of treatability studies that demonstrated reductions in the range of 96-99% using ET-1 only.

This study was significant because it revealed that chemical emulsifiers hinder the adsorption of target organics. A chemical de-emulsifier was required to break the pesticide emulsion prior to treatment. This situation has been repeated in the oilfield, when stabilized emulsions result in high oil carryover in produced water.

Toxicity of ET-1 and Crude Oil

Acute toxicity tests were conducted in 1993 on mysid shrimp. Crude oil, ET-1 organoclay, and 1:1 mixtures of both were evaluated. The tests showed that the addition of 50% organoclay reduced the toxicity (LC50) of the crude oil sample by sixfold; from 0.01548 g/l to over 0.1 g/l. Further testing demonstrated that the toxicity of crude oil to mysids stopped immediately upon the application of organoclay to the floating oil. The laboratory noted that a reduced dissolved-oxygen content in the water caused by the floating saturated media might have been as much a factor in mortality.

Desorption / TCLP Testing

The desorption and TCLP properties of spent ET-1 have also been investigated. TCLP extraction tests have demonstrated that spent ET-1 in an aqueous solution will not leach adsorbed aromatic hydrocarbons and that spend media might be classified in the United States as a non-hazardous waste.

Efficacy of Hydrocarbon Adsorption by Organoclay

Field tests and operating data have provided us with the following commercial removal rates for petroleum hydrocarbons:

*Since free oil can be measured by EPA 413.1, EPA 1664, or by EPA 418.1, a more detailed evaluation of these results is not possible.
The relationship between influent concentration and effluent is presented in Figures 1-4. Removal rate in percent is defined by the ratio of effluent concentration to influent concentration for each constituent. The data is derived from the case studies described herein, and also from other non-oilfield projects.