Discussion of Chicgoua Noubactep on “Removal of thiobencarb in aqueous solution by zero valent iron” by Md. Nurul Amin et al. [Chemosphere 70 (3) (2008) 511–515]

The following comments are proposed to clarify some related issues on the use of zero valent iron micrometric particles for the treatment of a thiobencarb pesticide solution published in a recent article by Nurul Amin et al., [Nurul Amin Md., Kaneco, S., Kato, T., Katsumata, H., Susuki, T., Otha, K., 2008. Removal of thiobencarb in aqueous solution by zero valent iron. Chemosphere 70 (3), 511–515], and discussed later by Chicgoua Noubactep.     

Facile synthesis of Ag-modified manganese oxide for effective catalytic ozone decomposition

O₃ decomposition catalysts with excellent performance still need to be developed. In this study, Ag-modified manganese oxides (AgMnO_x) were synthesized by a simple co-precipitation method. The effect of calcination temperature on the activity of MnO_x and AgMnO_x catalysts was investigated. The effect of the amount of Ag addition on the activity and structure of the catalysts was further studied by activity testing and characterization by a variety of techniques. The activity of 8%AgMnO_x for ozone decomposition was significantly enhanced due to the formation of the Ag_1.8Mn₈O₁₆ structure, indicating that this phase has excellent performance for ozone decomposition. The weight content of Ag_1.8Mn₈O₁₆ in the 8%AgMnO_x catalyst was only about 33.76%, which further indicates the excellent performance of the Ag_1.8Mn₈O₁₆ phase for ozone decomposition. The H₂ temperature programmed reduction (H₂-TPR) results indicated that the reducibility of the catalysts increased due to the formation of the Ag_1.8Mn₈O₁₆ structure. This study provides guidance for a follow-up study on Ag-modified manganese oxide catalysts for ozone decomposition.     

Synthesis, characterization and application of Lagerstroemia speciosa embedded magnetic nanoparticle for Cr(VI) adsorption from aqueous solution

Lagerstroemia speciosa bark (LB) embedded magnetic nanoparticles were prepared by co-precipitation of Fe²⁺ and Fe³⁺ salt solution with ammonia and LB for Cr(VI) removal from aqueous solution. The native LB, magnetic nanoparticle (MNP), L. speciosa embedded magnetic nanoparticle (MNPLB) and Cr(VI) adsorbed MNPLB particles were characterized by SEM–EDX, TEM, BET-surface area, FT-IR, XRD and TGA methods. TEM analysis confirmed nearly spherical shape of MNP with an average diameter of 8.76 nm and the surface modification did not result in the phase change of MNP as established by XRD analysis, while led to the formation of secondary particles of MNPLB with diameter of 18.54 nm. Characterization results revealed covalent binding between the hydroxyl group of MNP and carboxyl group of LB particles and further confirmed its physico-chemical nature favorable for Cr(VI) adsorption. The Cr(VI) adsorption on to MNPLB particle as an adsorbent was tested under different contact time, initial Cr(VI) concentration, adsorbent dose, initial pH, temperature and agitation speed. The results of the equilibrium and kinetics of adsorption were well described by Langmuir isotherm and pseudo-second-order model, respectively. The thermodynamic parameters suggest spontaneous and endothermic nature of Cr(VI) adsorption onto MNPLB. The maximum adsorption capacity for MNPLB was calculated to be 434.78 mg/g and these particles even after Cr(VI) adsorption were collected effortlessly from the aqueous solution by a magnet. The desorption of Cr(VI)-adsorbed MNPLB was found to be more than 93.72% with spent MNPLB depicting eleven successive adsorption–desorption cycles.     

Triton X-100 induced cuboid-like BiVO4 microsphere with high photocatalytic performance

A highly active visible light-induced BiVO₄ photocatalyst was prepared by a simple co-precipitation method using ammonia solution as a pH adjustor and Triton X-100 (TX100) as a structure directing agent. The physical properties of the prepared BiVO₄ photocatalyst were investigated by several techniques such as X-ray diffractometer (XRD), Brunauer–Emmett–Teller (BET) surface area measurement, scanning electron microscopy (SEM), energy dispersive analysis (EDS), Fourier-transformed infrared spectroscopy (FT-IR), photoluminescence (PL), and UV–Vis diffused reflectance spectroscopy (DRS). XRD results revealed the existence of a monoclinic scheelite structure in both the unmodified and the modified samples. The TX100 played a crucial role to control the cuboid-like shape morphology of BiVO₄. The DRS results showed that the as-prepared cuboid BiVO₄ possessed enhanced visible light absorption range compared with that of the unmodified BiVO₄. The photocatalytic activity was evaluated via indigo carmine (IC) degradation under visible light irradiation. The modified BiVO₄ showed higher photocatalytic efficiency than the unmodified BiVO₄ and the commercial P25-TiO₂ which could be ascribed to the better charge separation efficiency.     

Study on the mechanism of copper–ammonia complex decomposition in struvite formation process and enhanced ammonia and copper removal

Heavy metals and ammonia are difficult to remove from wastewater, as they easily combine into refractory complexes. The struvite formation method (SFM) was applied for the complex decomposition and simultaneous removal of heavy metal and ammonia. The results indicated that ammonia deprivation by SFM was the key factor leading to the decomposition of the copper–ammonia complex ion. Ammonia was separated from solution as crystalline struvite, and the copper mainly co-precipitated as copper hydroxide together with struvite. Hydrogen bonding and electrostatic attraction were considered to be the main surface interactions between struvite and copper hydroxide. Hydrogen bonding was concluded to be the key factor leading to the co-precipitation. In addition, incorporation of copper ions into the struvite crystal also occurred during the treatment process.     

Fluoride removal by Al, Ti, and Fe hydroxides and coexisting ion effect

Batch experiments were conducted to evaluate fluoride removal by Al,Fe,and Ti-based coagulants and adsorbents,as well as the effects of coexisting ions and formation of aluminum–fluoride complexes on fluoride removal by co-precipitation with alum(Al_2(SO_4)_3·18H_2O).Aluminum sulfate was more efficient than the other coagulants for fluoride removal in the pH range between 6 and 8.Nano-crystalline TiO_2 was more effective for fluoride removal than Al and Fe hydroxides in a pH range of 3–5.Coexisting anions in water decreased the removal of fluoride in the order:phosphate(2.5 mg/L) arsenate(0.1 mg/L) bicarbonate(200 mg/L) sulfate(100 mg/L) = nitrate(100 mg/L) silicate(10 mg/L) at a pH of 6.0.The effect of silicate became more significant at pH 7.0.Calcium and magnesium improved the removal of fluoride.Zeta-potential measurements determined that the adsorption of fluoride shifted the PZC of Al(OH)_3 precipitates from 8.9 to 8.4,indicating the chemical adsorption of fluoride at the surface.The presence of fluoride in solution significantly increased the soluble aluminum concentration at pH 6.5.A Visual MINTEQ modeling study indicated that the increased aluminum solubility was caused by the formation of AlF~(2+),AlF~(+2),and AlF_3complexes.The AlF_x complexes decreased the removal of fluoride during co-precipitation with aluminum sulfate.     

中子活化分析环境样品干扰元素的分离

环境样品使用中子活化法分析,在γ多道测量过程中,常有干扰发生。若将铜载体加入松叶分解液中,可与CH_3CSNH_2反应形成硫化物沉淀,在共沉淀过程中可去除干扰元素。在不同的pH条件下,松叶中各种被测元素的回收率不同。使用放射性核素示踪方法测量,当pH增大时,Ag、Cd和Cu的回收率随之增大,而Sb和As的回收率将减小,Hg的回收率变化不大。     

Photocatalytic degradation of endocrine disruptor Bisphenol-A in the presence of prepared CexZn1-xO nanocomposites under irradiation of sunlight

Photocatalytic degradation of Bisphenol A （BPA）, a representative endocrine disruptor chemical, was carried out under irradiation of sunlight in the presence of CexZn1-xO nanophotocatalyst. Cerium （Ce） ions were successfully incorporated into the bulk lattice of ZnO by simple co-precipitation process. The CexZn1-xO composite nanostructures exhibited higher photocatalytic efficiency than pure ZnO in the degradation of BPA under sunlight irradiation and nearly complete mineralization of BPA was achieved. The degradation rate was strongly dependent on factors such as the size and structure of catalyst, doping material concentration, BPA concentration, catalyst load, irradiation time and pH levels. This work suggested that the CexZn1-xO assisted photocatalytic degradation is a versatile, economic, environmentally benign and efficient method for BPA removal in the aqueous environment.     

共沉富集─单缝石英管火焰原子吸收法测定水中痕量铜、铅、锌、镉

采用共沉富集与单缝石英管技术，以火焰法测定地面水、地下水中的痕量铜、铅、锌、镉，检测限分别为０．５，１．８，０．２，０．１μｇ／Ｌ，四种痕量元素１１次测定的变异系数分别２．８％，２．３％，３．１％和３．９％。