Enhanced degradation rate

Once in the soil, deactivation is related to kind and quantity of clay and to organic matter content (Upchurch and Mason 1962 Day et al, 1968 Weber et al, 1969). Burnside et al. (1961) reported that simazine remains in the upper few centimeters of soil and breaks down readily at high temperatures and low pH. Holly and Roberts (1963) emphasized the variability in the breakdown of simazine. In one study, simazine residue in soil was evaluated 1 year after treatment, where the half-life was 59 days. However, after 12 years of treatment, the half-life was 46 days, a slight but significant enhanced degradation rate (Rouchard et al, 2000). 

In order to further profit from the dual complexing ability of CDs, we have studied Fenton-type processes in the presence of CDs. Several classes of compounds showed enhanced degradation rates in the presence of CDs in aqueous solution PCBs, PAHs, TNT, and chlorinated phenoxyacetic acids [38,102]. Dissolved natural organic matter typically inhibits Fenton degradation by sequestering the iron away from the pollutant [31,32]. However, addition of cyclodextrins overcame the inhibitory effect of the NOM and resulted in enhanced degradation rates [38]. 

There is evidence from a relatively few studies to show that repeated treatments of 2,4-D and MCPA result in enhanced degradation rates under field conditions as a result of adaptation of soil microorganisms. Even less is known about the phenomenon of cross-enhancement under field conditions, where previous applications of either 2,4-D and MCPA may result in enhanced breakdown of both phenoxyalkanoic herbicides. 

Table IV. Rhodanese activity of soils with enhanced degradation rates of EPTC and Butylate...

In order to have a practical application of these systems, both the use of visible light source and an enhanced degradation rate are essential. Doped Ti02 semiconductors show photocatalytic activity for the photodegradation of phenol and chlorophenol using visible light [41, 43, 44, 75]. 

Our approach is to use the inexpensive ligands that are already used industrially as well as conventional solvents. The goal of this project is to develop a thermomorphic approach to the rhodium-catalyzed hydroformylation of higher olefins (>Ce) that enhances conversion rates and ease of product recovery while minimizing catalyst degradation and loss. 

Wu et al. [12] used both microwave (MW) and ultrasound (US) methods individually and in combination to examine the combined effect. The rapid thermal effect of MW could be seen on polar chemicals and more OH radicals were produced due to US. Microwave irradiations have shown enhanced degradation effect when applied with sonication in absence of additional catalyst though the rate increased more in presence of H2O2. The rate order was found to be MW-US > MW > US. 

Standley SM, Kwon TJ, Murthy N et al (2004) Acid-degradable particles for protein-based vaccines Enhanced survival rate for tumor-challenged mice using ovalbumin model. Bioconjug Chem 15 1281-1288... 

PAHs are widely distributed in the environment as evidenced by their detection in sediments, soils, air, surface waters, and plant and animal tissues. However, the ecological impact of PAHs is uncertain. PAHs show little tendency for bioconcentration despite their high lipid solubility (Pucknat 1981), probably because most PAHs are rapidly metabolized. Sims and Overcash (1983) list a variety of research needs regarding PAHs in soil-plant systems. Specifically, research is needed to establish the rates of PAH decomposition in soils the soil PAH levels above which PAH constituents adversely affect the food chain and enhancement factors that increase degradation rates of PAHs, especially PAHs with more than three rings. Once these factors have been determined, PAH disposal into soils may become feasible at environmentally nonhazardous levels. 

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