W. David Constant

Aqueous solubility enhancement and desorption of hexachlorobenzene from soil using a plant-based surfactant

A plant-based surfactant extracted from fruit pericarps of Sapindus mukorossi (Ritha) is proposed for remediation of contaminated soil from a local hazardous waste site. Natural surfactants can be prepared using a very simple water extraction of fruit pericarp powder. Natural surfactant solutions are employed to enhance the aqueous solubility of a hydrophobic organic compound, hexachlorobenzene (HCB), and to desorb HCB from soils in batch and one-dimensional flow-through soil column experiments. The solubility of HCB in natural surfactant solutions increased linearly with surfactant concentration beyond the critical micelle concentration. The mass of dry Ritha powder required to solubilize 1 mg of HCB in 1 liter of water was comparable to sodium dodecylsulfate solution and other commercial surfactants. HCB concentration in the aqueous solutions approached 90% of the HCB solubility in the respective natural surfactant solutions when soils contaminated to high levels were used for desorption. HCB recovery was up to 90% of the total HCB for soils contaminated with lower levels. Desorption behavior observed for natural surfactant solutions was similar to SDS solutions. Natural surfactant solutions performed more efficiently than a simple water flood in recovering HCB from one-dimensional soil columns. The HCB concentration in the effluent was found to be as high as 80% of the surfactant-enhanced HCB solubility in respective solutions. The results of this study provide a strong case for pursuing natural surfactant solutions in further research.

Soil flushing of residual transmission fluid: Application of Colloidal Gas Aphron suspensions and conventional surfactant solutions

Abstract An innovative technology using Colloidal Gas Aphrons (CGAs) is applied in this study to flush residual levels of a light non-aqueous phase liquid (LNAPL) such as automatic transmission fluid (ATF) from a Superfund site soil. Performance of CGA suspensions is compared with that of conventional aqueous anionic surfactant solutions under both gravity stable (downflow) and gravity unstable (upflow) conditions. CGA suspensions were found to be more effective in washing ATF under both downflow and upflow modes. The displacement of ATF from the soil pores seems to be the mechanism of removal in the case of water floods. Increasing the surfactant concentration did not increase the removal rate correspondingly. The pressure required to pump the CGA suspension was much lower than that required for conventional surfactant solutions or water flood. Results show enough promise that more research should be directed at this potential technology for in situ remediation of contaminated aquifers.

Soil flushing using colloidal gas aphron suspensions generated from a plant-based surfactant

Abstract Natural surfactant solutions obtained from the fruit pericarps of Sapindus mukorossi , commonly known as Ritha or soapnut, are tested for their ability to remove hydrophobic organic compounds (HOCs) from soil. Colloidal gas aphron (CGA) suspensions generated using the surfactant are used in this study to flush an HOC from a representative soil. Soil is spiked with a chlorinated hydrocarbon, hexachlorobenzene (HCB), serving as a model HOC representative of contamination at a Superfund site north of Baton Rouge, LA. The recovery of HCB from soil columns using CGA suspensions was considerably larger than that for a waterflood. HCB recoveries in the effluent reached a maximum by the fifth pore volume and remained fairly constant for soils contaminated with high levels of HCB. This maximum HCB concentration in the column effluent was proportional to HCB solubility in the corresponding surfactant solutions. Natural surfactant performed marginally better in the form of conventional solutions than CGA suspensions at similar concentration in recovering HCB. HCB removal increased with increasing surfactant concentration due to increased aqueous solubility. The pressure buildup across the soil column remained fairly low when natural surfactant was used at concentrations up to 1%. Alternating the flushing media between CGA and water neither enhanced the recovery of HCB nor changed the pressure buildup across the soil column.

AN INVESTIGATION OF THE FACTORS INFLUENCING TRANS [ENT INTERFACIAL TENSION BEHAVIOR IN CRUDE OIL/ALKALINE WATER SYSTEMS

Abstract The interfacial tension (IFT) dynamics of crude oil/alkaline water systems have been examined using the spinning drop interfacial tensiometer. Both synthetic and natural crudes were employed in the study; however, it was found that synthetic crudes frequently exhibited behavior quite different from that observed with natural crudes. Two crude oils were fractionated and the interfacial tension behavior of the fractions against alkaline water was investigated. Interfacial tension reduction was related to the presence of carboxylic acid components. The stabilities of the interfacial tension minima with time were related to the water solubility of the surface active species, and the ease of formation of their surface inactive, undissociated acid salts, as well as, the temperature and oil viscosities. The use of the spinning drop interfacial tensiometer in evaluating the IFT behavior of crude oil/alkaline systems was assessed.

Nutrient and surfactant enhancement for the biodegradation of chlorinated hydrocarbons in the wastewater from a Louisiana Superfund site

Abstract Surfactant based soil washing and flushing is an emerging technology for Superfund site remediation in the United States. The presence of surfactants in the wastewater, however, poses challenging problems for subsequent biological or physical–chemical processes. The objective of this research is to evaluate the potential effects of selected surfactants on the biodegradation of chlorinated hydrocarbons in the wastewater from the Petro Processors (PPI) Superfund site north of Baton Rouge, LA. Results from this study showed that biodegradation of a real world waste containing a broad array of hazardous contaminants was significantly enhanced by the amendment of mineral nutrients and surfactants, especially a nonionic surfactant Witconol. The enhancement based on TOC reduction was 49% higher for the mixture of PPI wastewater with Witconol than the combined biodegradation of PPI wastewater and Witconol alone, whereas a similar enhancement was observed with an anionic surfactant sodium dodecylsulfate (SDS). The addition of mineral nutrients was also shown to further enhance the biodegradation of PPI wastewater, with a 13% increase in TOC reduction as compared to the nutrient limited controls. Nutrient addition significantly increased microbial growth, biodegradation, and foam degradation of surfactant-laden PPI wastewater.

Alcohol-assisted alkaline flooding for enhanced oil recovery

Abstract Alcohol additives were found to improve alkaline flood performance under certain conditions. Only crude oils that emulsified during alkaline flooding were more efficiently recovered with alcohol. Improved recovery with alcohol was attributed to modification of emulsion characteristics. Alcohol additives reduced emulsion viscosities and accelerated emulsion coalescence rates, which improved oil bank stability and promoted oil recovery. Oil recovery efficiency was affected by the chemical structure of the alcohol. Oil recovery generally improved with increasing molecular weight from methanol to butanol and then decreased for the less water soluble pentanol isomers. Alcohol additives were found to affect the interfacial shear viscosities (IFSV) and interfacial tensions (IFT) of crude oil/alkaline water systems. Improvements in recovery efficiency was found to correspond directly to reduced IFSV. Poor recovery was also related to elevated interfacial tensions.

Surfactant screening for soil washing: Comparison of foamability and biodegradability of a plant‐based surfactant with commercial surfactants

Abstract Batch shaker‐flask experiments using a consortium of sewage microorganisms were conducted to study the aerobic biodegradation of a plant‐based natural surfactant (Ritha) and four anionic / nonionic commercial surfactants. Foaming potential, foam decay, microbial growth and ultimate biodegradation (mineralization) of natural surfactant were compared to those of synthetic surfactants, namely anionic sodium dodecylbenzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS), and nonionic alcohol ethoxylate Tergitol 15‐S‐12 and Witconol SN‐90. The natural surfactant showed the lowest foaming potential among the selected surfactants (SDBS > SDS > Tergitol > Witconol > Ritha). The natural surfactant also performed better than commercial surfactants in terms of biodegradability at concentrations above critical micelle concentrations (supra‐CMCs). However, surface‐active components resisted biodegradation and foams from the natural surfactant were more persistent than SDS, Tergitol, and Witconol. Concurrent...

Stochastic modeling of flow and transport in deep-well injection disposal systems

Abstract The migration of deep-well injected waste in heterogeneous confining layers is evaluated using numerical simulation. Of primary concern is the migration potential through permeable sand paths between less permeable shale. The configuration of the predominantly shale confining layers was defined by Monte Carlo techniques assuming a binary random structure composed of pure sand and pure shale. Three-dimensional flow simulations using Modflow , a finite difference model, indicated that essentially continuous sand paths and unacceptably rapid transport might exist through confining layers with an average shale fractions of less than about 0.65 and that two and three dimensional flow simulations were essentially equivalent for high (>0.6-0.7) or low (

Hydrocracking of model coal-derived liquid components over a zeolite catalyst

Hydrocracking of fluorene was investigated over a nickel-loaded Y zeolite in a fixed-bed flow reactor using decalin as a donor solvent. Over the range of space-time and temperature variables investigated, no thermal reactions were observed, nor did hydrogen pressure significantly affect the kinetics. Deactivation (in part due to coking) was significant and coke formation was found to be a function of catalyst exposure time but was not included in the kinetic model, as the pathway for coke formation was unknown. Two kinetic models were developed using pseudo-homogenous rate expressions descriptive of the hydrocracking chemistry and an overall reaction mechanism was proposed taking into account the roles of the donor solvent, catalyst and hydrogen. The kinetic model incorporates three routes for the cracking of fluorene subsequent to hydrogen transfer from decalin : dealkylation of the side ring, breaking the phenyl-methyl bond of the central ring, and side-ring cracking. The product distribution consisted of benzenes, cyclopentanes, and C2-C6 hydrocarbon gases. Decalin was found to be more reactive than tetralin and avoided significant naphthalene production.

Integrated waste management via the Natural Laws

SummaryThe basic tools of engineering, energy and material balances and rate expressions, provide a pathway to apply the Natural Laws of Hazardous Waste for proper waste management. Overall, one must focus on natures limits, which are discussed, using open minded engineering practices for proper waste management. By expansion of balance concepts beyond ‘end-of-pipe’ and integrating concepts beyond basic life-cycles, as discussed in this paper, the true impact ofwaste management practices may be established. These cradle-to-grave balances are connected to natures limits via results of recent work by others on risk assessment. The combination of approaches for evaluating concentration limits of chemicals in the environment allows the facility for an engineering solution for proper waste management. The method is presented by making example comparisons of choices of technology for recycling, storage, and site remediation.