The main purpose of this study was to characterize the adsorption and desorption interactions of naphthalene, a model environmental organic pollutant, with C60 fullerene. C60 fullerene was used as a model adsorbent for carbonaceous nanoparticles. Typical batch reactors were used to perform adsorption and desorption experiments. Adsorption and desorption of naphthalene to and from C60 fullerene solids in different aggregation forms was studied, where C60 was used as purchased, deposited as a thin film, or dispersed in water by magnetic mixing. Adsorption and desorption of naphthalene to activated carbon, a common sorbent, was also studied and compared with that of C60. It was found in this study that the enhanced dispersal of C60 could affect the adsorption of naphthalene by several orders of magnitude. A solid-water distribution coefficient of 102.4 mL·g-1 was obtained for adsorption of naphthalene to poorly dispersed C60, whereas (104.2 to 104.3) ml·g-1 coefficients were obtained for well-dispersed C60 samples. In addition, desorption of naphthalene from dispersed C60 samples into aqueous solutions was found to exhibit strong hysteresis. For the desorption over a period of 60 days, only about 11% of total naphthalene was desorbed from C60. Possible mechanisms for these observations are discussed.

A semiempirical mathematical model has been developed to predict inhibitor efficiency for barium sulfate scale control in industrial processes. This model can be used for selecting effective inhibitors and determining the minimal effective concentration needed for a given system. The model incorporates experimental data of the nucleation and inhibition kinetics. Specifically, the induction period in the presence and absence of scale inhibitors has been measured experimentally and inputted into the model:  C inh = (1/b) log[t inh/t 0], where C inh is the inhibitor concentration, t inh is the inhibition time (e.g., 20 min), t 0 is the nucleation induction period of the scaling mineral crystal, and b is the inhibitor efficiency. The inhibition kinetics of barium sulfate nucleation with bis(hexamethylene)triaminepenta(methylenephosphonic acid) (BHMTPMP) and several other polyphosphonate and polyacrylate inhibitors have been measured. Many factors which are important to nucleation and inhibition kinetics, such as the degree of supersaturation, temperature, and solution pH, have been included in the inhibitor model. The model prediction for barium sulfate scale control was in good agreement with laboratory observations and field experience.

In natural sediments, the majority of heavy metal ions are generally associated with the solid phase. To become bioavailable, the metal ions must desorb from the solid. Numerous studies of heavy metals in sediments have suggested that sorption and desorption exhibit hysteresis (i.e., the two processes are not reversible), while other studies have suggested that desorption hysteresis does not exist. In this study, sorption/desorption hysteresis of lead (Pb) and cadmium (Cd) was evaluated over the following range of conditions: (i) desorption induced by replacing the supernatant liquid with contaminant-free electrolyte solution; (ii) desorption induced by lowering the solution pH with mineral acid; and (iii) desorption induced by sequestration with EDTA. Given the importance of dissolved organic and inorganic ligands in regulating heavy metal behavior in nature sediments, sorption/desorption experiments were conducted on both untreated and prewashed sediments. Prewashing treatment increases the sorption potential of Cd but not Pb. Desorption hysteresis is observed in both the untreated and the prewashed sediments using the replaced supernatant method, and the desorption hysteresis appears to increase with aging time. Hysteresis is not observed when desorption is initiated by lowering the solution pH. A large fraction of the sorbed heavy metal ions can be easily desorbed by EDTA; between 0.04 and 1.2 mmol/kg Cd and Pb ions are resistant to desorption.

A surrogate sediment was developed to reduce some of the complexity in the structural aspects of the adsorbed organic carbon phase. Layers of an anionic surfactant were sorbed to colloidal anatase to produce an organic carbon phase that had hydrophobic regions and resisted desorption. The surrogate is verified as a model sediment by comparing the results of contaminant [2,2′,5,5′-tetrachlorobiphenyl (PCB) and naphthalene] adsorption and desorption batch experiments to the results of similar experiments performed on a well-studied natural sediment. The surrogate exhibited adsorption of contaminants via a hydrophobic interaction in the same magnitude as to a natural sediment for the two different hydrophobic organic contaminants in 0.1 or 0.15 M NaCl solution. The sorption of PCB to the surrogate at varied organic carbon contents was observed to follow a linear adsorption isotherm. Desorption experiments were conducted by successive dilutions. Both the surrogate and natural sediment were observed to exhibit similar desorption behavior. The solution concentration during desorption was lower than predicted by the adsorption isotherm and remained unchanged from 4 h to 168 days. The heterogeneous nature of sediments should be greatly reduced in the surrogate yet desorption still appears to be low.

Phosphonates are commonly used in the petroleum industry to Phosphonates are commonly used in the petroleum industry to control scale and corrosion. In order to understand the fate of phosphonates in the reservoir after an inhibitor squeeze, both the phosphonates in the reservoir after an inhibitor squeeze, both the kinetics and the equilibrium aspects of phosphonate sorption have been studied in the laboratory using batch apparatus and sandstone core flow-through apparatus. Diethylenetrianiinepenta(methylene phosphonic acid) (DTPMP) was used in the experiments. The phosphonic acid) (DTPMP) was used in the experiments. The adsorption process includes the following four stages:molecular diffusion;dissolution of mineral from sandstone surfaces;adsorption; andsolid phase maturation. The adsorption is kinetically important and the amount adsorbed is affected by both flow velocity and calcium concentration. A new radial-flow transport equation to simulate the transport of phosphonate in an inhibitor Squeeze is also reported. phosphonate in an inhibitor Squeeze is also reported. An inhibitor squeeze is a common procedure used in the gas and oil industry to control scale. In most squeezes, thirty percent, or more, of the inhibitor is returned in the first day of production. Then the inhibitor concentration levels off to a steady value of about 5 mg/l, or less. Previously, researchers at Rice University sponsored by Gas Research Institute, designed an inhibitor squeeze for the Department of Energy (DOE) geothermal-geopressured Gladys McCall well near Grand Chanier, Louisiana. The producing formation for this well at about 16,000 ft is silica producing formation for this well at about 16,000 ft is silica cemented and does not contain a detectable amount of the calcite. When brine production was over 15,000 BPD, the pressure draw down was such that the well produced heavy calcite scale in the top several thousand feet of the production tubing and had to be acidized. Following the phosphonate inhibitor squeeze the Gladys McCall well produced more than eighteen million barrels of brine at 20,000 to 30,000 BPD without scale formation. The same inhibitor design has since been successfully repeated at the Gladys McCall well and at another DOE design well, the Pleasent Bayou well No. 2 near Alvin, Texas. The mechanism of inhibitor flow-back following an inhibitor squeeze is not well understood. The objective of this research is to establish the governing mechanism of inhibitor transport following a squeeze, which can be used to enhance the efficiency of a squeeze design. Both precipitation and adsorption are possible mechanisms governing the low inhibitor flow-back concentration. The solubility of calcium phosphonate has been studied in this laboratory, and the value is much higher than the equilibrium flow-back concentration. Therefore, the controlling mechanism is either an adsorption phenomenon or a more complicated precipitation process. In this study, column flow-through experiments have been done to study the sorption of phospnonate to Berea sandstone. phospnonate to Berea sandstone. In general, the approach of this work has been to use one dimensional column and batch experiments to measure fundamental interaction parameters for inhibitors and to use these parameters in radial models to examine their impact on squeezes and production. Then, based upon these simulations field squeezes have been designed, implemented, and monitored. TRANSPORT EQUATIONS The transport of chemicals in porous media is governed by velocity, hydrodynamic dispersion, and reactions. For nonreactive materials injected into a well or flowing back from a reservoir, flow is radial. The corresponding radial flow transport equation (Eq. 1) is: (1) where C is the solution phase chemical concentration, t is time; D is dispersion coefficient; r is radius; and Vw is the velocity of water at r. P. 747