The photodegradation of methyl orange (MO) was investigated in aqueous suspension containing titania nanoparticles with mesostructures(m-TiO2) under UV irradiation. The experimental results show that 98% MO can be mineralized in the 1.0 g l_1 m-TiO2 suspension(pH 2.0) after 45 min illumination. Particular attention was devoted to the identification and the transformation of the fragmentsretaining the chromophoric group. The photodegradation mechanism of the quinonoid MO mainly involves three intermedial processes:demethylation, methylation and hydroxylation. Among those processes, demethylation is more favorable than the hydroxylation, but thehydroxylation results in the largest number of intermediates. The degradation pathway of quinonoid MO under the optimal conditions isalso proposed.

Mesoporous titania nanoparticles with high specific surface area and thermal stable anatasewallwas synthesized from surfactant laurylaminehydrochloride (LAHC) and inorganic precursor Ti(SO4)2. The as-synthesized and calcined materials were characterized by X-ray diffraction, nitrogen adsorption-desorption, transmission electron micrographs, Fourier transform infrared spectroscopy and thermogravimetric analysis.The obtained mesoporous TiO2 nanoparticles have mean diameter of 25.5 nm. The specific surface area of the mesoporous nanosized TiO2calcined at 400◦C exceeded 189m2 g−1, and that of the samples after calcinations at 500◦C still have 151m2 g−1. The obtained anatasemesoporous TiO2 nanoparticles show relative high thermal stability.

Adsorption and desorption of salmon sperm DNA on four different colloidal fractions from Brown Soil and clay minerals were studied.The adsorption isotherms of DNA on the examined soil colloids and minerals conformed to the Langmuir equation. The amount of DNAadsorbed followed the order: montmorillonite[fine inorganic clayOfine organic clayOkaoliniteOcoarse inorganic clayOcoarse organicclay. A marked decrease in the adsorption of DNA on organic clays and montmorillonite was observed with the increase of pH from 2.0 to5.0. Negligible DNA was adsorbed by organic clays above pH 5.0. As for inorganic clays and kaolinite, a slow decrease in DNA adsorptionwas found with increasing pH from 2.0 to 9.0. The results implied that electrostatic interactions played a more important role in DNAadsorption on organic clays and montmorillonite. Magnesium ion was more efficient than sodium ion in promoting DNA adsorption on soilcolloids and minerals. DNA molecules on soil colloids and minerals were desorbed by sequential washing with 10 mM Tris, 100 mM NaCland 100 mM phosphate at pH 7.0. A percentage of 53.7–64.4% of adsorbed DNA on organic clays and montmorillonite was released, whileonly 10.7–15.2% of DNA on inorganic clays and kaolinite was desorbed by Tris and NaCl. The percent desorption of DNA from inorganicclays, organic clays, montmorillonite and kaolinite by phosphate was 39.7–42.2, 23.6–28.8, 29.7 and 11.4%, respectively. Data from thiswork indicated that fine clays dominate the amount of DNA adsorption and coarse clays play a more important role in the binding affinity ofDNA in soil. Organic matter may not favor DNA adsorption in permanent-charge soil. The information obtained is of fundamentalsignificance for the understanding of the ultimate fate of extracellular DNA in soil.

DNA is the genetic material of various organisms. Extracellular DNA adsorbed or bound on surface-active particlesin soils has been shown to persist for long periods against nucleases degradation and still retain the ability to transformcompetent cells. This paper reviews some recent advances on the binding and transformation of extracellular DNA in soils,which is fundamental to understanding the nature of the soil, regulating biodiversity, and assessing the risk of releasinggenetically engineered microorganisms (GEMs) as well as being helpful for development of the genetic evolutional theoryof bacteria. Several influencing factors, such as soil pH, ionic strength, soil surface properties, and characteristics of theDNA polymer, are discussed. To date, the understanding of the type of molecular binding sites and the conformation ofadsorbed and bound DNA to soil particles is still in its infancy.

In this work, the adsorption properties ofcrosslinked chitosan for Mo(VI) were studied. The adsorptionrate of Mo(VI) by CCTS was 97% at pH 3.0. Adsorptionbalance time, elution conditions, the effect of coexisting elements,and the adsorption mechanism were investigated. Anovel method of ultratrace Mo(VI) preconcentration withCCTS and determination by graphite furnace atomic absorptionspectrometry was found. The detection limit (3_, n_ 10) of the method was 0.040 _g L_1, and the relativestandard deviation was 2.98% at 1.00 _g L_1. The methodhas been applied to the determination of Mo(VI) in environmentalwater samples, with satisfactory results.