Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.

Heavy metal chemistry in soils received long-term application of organic wastes

This study was carried out to understand the long-term effect of organic waste treatment on the fate of heavy metals originated from the organic wastes, together with examination of changes in soil properties. For this, the soils received three different organic wastes (municipal sewage sludge, alcohol fermentation processing sludge, pig manure compost) in three different rates (12.5, 25, 50 ton/ha/yr) for 7 years (1994 - 2000) were used. To see the long-term effect, plant growth study and soil examination were conducted twice in 2000 and 2010, respectively. There was no additional treatment of organic wastes for post ten years after ceasing organic waste treatment for seven years. Soil examination conducted in 2010 showed decreases in soil pH, EC, total nitrogen, organic matter, available phosphorus, exchangeable cations and heavy metal contents in all soils received organic wastes compared to the results obtained in 2000. Speciation of heavy metals in soil through sequential extraction showed that organically bound Cu was the dominant species in all treatment and exchangeable Cu was increased in the plots treated with municipal sewage sludge and alcohol fermentation processing sludge. organically bound Ni increased from 25% - 30% to 32% - 45% in 2010 inall treatment while Pb showed increase in carbonate form in all treatments. Zn existed mainly as sulfide and residual forms, showing increases in organically bound form in all treatment during post ten years.

Tribology of WC reinforced SiC ceramics: Influence of counterbody

Hot pressed silicon carbide(SiC) composites prepared with 0, 10, 30 or 50 wt% tungsten carbide(WC) are subjected to dry sliding wear against WC-Co and steel ball. In particular an attempt has been made to answer the following important questions:(i) How does the load(from 5 to 20 N) effect sliding wear behaviour of SiC-ceramics against WC-Co and steel counterbodies?(ii) Is there any effect of WC content on friction and wear characteristics of SiC ceramics?(iii) Does the dominant material removal mechanism of SiC ceramics change with the addition of WC or counterbody?(iv) What is the influence of mechanical properties on the sliding wear? Experimental results indicated that coefficient of friction(COF) for the SiC ceramics varied between 0.66 and 0.33 with change in load and counterbodies. Wear volume for SiC ceramics found approximately 6-10 times more against WC-Co as compared against steel. Wear volume changes from 2.0 × 10^(–3)mm^3 to 1.2 × 10^(–2)mm^3 with change in counterbodies for SiC -(10, 30 or 50 wt%) WC composite at 20 N. SiC ceramics indicated abrasion and composites reveal tribochemical wear as major material removal mechanisms. Wear is influenced by the hardness of counterbody and fracture toughness of SiC -WC composites.