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Several modified clays have been designed and created for selective removal and recovery of heavy metals such as Cd, Cu, Cr, etc. These surfactant−clay complexes were prepared using hectorite or montmorillonite as the base clay. A simple two-step approach has been developed to synthesize these modified-clay complexes through ion exchange and hydrophobic anchoring of several surfactants such as long-chain alkyldiamines, long-chain dialkylamines, and long-chain carboxylic acids onto the clay matrices. The adsorption capacities and affinity constants of the modified clays can be found to approach those of commercial chelating resin (Chelex 100, Bio-Rad). Using cadmium as a model metal and montmorillonite−cetylbenzyldimethylammonium−palmitic acid (M−CBDA−PA) as a model modified-clay complex, the maximum adsorption capacity of the modified clay is found to be 42 ± 0.8 mg/g of clay and the affinity constant is 3.0 ± 0.1 mg/L. The metal adsorption has been shown to be mainly through chemical complexation rather than ion exchange. The immobilization of the metal ions is pH dependent, and thus, pH can act as a molecular switch to regenerate the modified-clay complexes.

The extracellular enzymes and cell mass from the pregrown Phanerochaete chrysosporium cultures were used for the degradation of PCP. The use of both extracellular enzymes and cell mass resulted in extensive mineralization of PCP, while the action of only the crude extracellular enzymes led to the formation of a degradation intermediate (TCHD). A kinetic model, which describes the relationship among PCP degradation, initial PCP concentration, dosage of extracellular enzymes, and cell mass concentration, was developed. Based on this model, various effects of initial PCP concentration, dosage of extracellular enzymes, and cell mass concentration were evaluated experimentally. It was found that when initial PCP concentration is lower than 12 mumol/L, the model of a parallel-series first-order reaction is sufficient to describe the degradation process. PCP disappearance and mineralization were enhanced by increasing either the extracellular enzyme concentration or the cell mass concentration. As high as 70% of PCP mineralization could be obtained by using a higher dosage of extracellular enzymes and cell mass. Various parameters of the kinetic model were determined and the model was verified experimentally. Simulation using this model provided the criteria needed to choose rational dosages of extracellular enzymes and cell mass for the degradation of PCP. Data reported allow some insight into the function of the extracellular enzymes and cell mass of P. chrysosporium in degradation processes of toxic pollutants and assist in the design and evaluation of practical bioremediation methods.