共查询到4条相似文献,搜索用时 0 毫秒
1.
We report the formation of bromoform in TiO2 suspensions (P25) under simulated solar UV irradiation at different concentrations of photocatalyst (0.5-1.5 g L−1) as well as initial concentrations of bromide ions (1-3 mg L−1) and 2,4-dihydroxybenzoic acid (2-10 mg L−1). The extent of bromoform formation (3-17 μg L−1) was most strongly affected by the amount of photocatalyst present and by the initial bromide concentration, increasing either of which leads to increased bromoform formation. Important interaction effects were observed when simultaneously increasing the concentrations of TiO2 and bromide as well as of bromide and DHBA. The time it takes for bromoform to appear in measurable concentrations in the irradiated TiO2 suspensions was between 10 and 90 min and most strongly depended on the initial concentration of dissolved organic carbon present in the suspensions, along with the amount of photocatalyst, also in interaction with the initial bromide concentration. 相似文献
2.
The adsorption of the taste and odour (T&O) compounds geosmin and 2-methylisoborneol (2-MIB) onto powdered activated carbon (PAC) has been studied under conditions which are typical for a drinking water treatment plant that uses reservoir water for drinking water production. The reservoir water as well as the pre-treated water (after flocculation) contains NOM that competes with the trace compounds for the adsorption sites on the carbon surface. Although the DOC concentrations in the reservoir water and in the pre-treated water were different, no differences in the competitive adsorption could be seen. By using two special characterisation methods for NOM (adsorption analysis, LC/OCD) it could be proved that flocculation removes only NOM fractions which are irrelevant for competitive adsorption.Different model approaches were applied to describe the competitive adsorption of the T&O compounds and NOM, the tracer model, the equivalent background compound model, and the simplified equivalent background compound model. All these models are equilibrium models but in practice the contact time in flow-through reactors is typically shorter than the time needed to establish the adsorption equilibrium. In this paper it is demonstrated that the established model approaches can be used to describe competitive adsorption of T&O compounds and NOM also under non-equilibrium conditions.The results of the model applications showed that in particular the simplified equivalent background compound model is a useful tool to determine the PAC dosage required to reduce the T&O compounds below the threshold concentration. 相似文献
3.
Rivera-Utrilla J Méndez-Díaz J Sánchez-Polo M Ferro-García MA Bautista-Toledo I 《Water research》2006,40(8):1717-1725
A study was conducted on the efficacy of the system based on the simultaneous use of ozone and powdered activated carbon (PAC) in removing sodium dodecylbenzenesulphonate (SDBS) from drinking waters and on the influence of operational parameters (PAC dose, ozone dose and presence of radical scavengers [HCO3-]) on this process. Results obtained showed that low doses of PAC during SDBS ozonation markedly increased the rate of SDBS removal from the medium. These results are due to the combined effect of two processes: (i) SDBS adsorption on the activated carbon surface and (ii) transformation of the dissolved ozone into .OH radicals. At higher ozone and PAC doses, there was a higher rate of SDBS removal from the medium. The presence of HCO3- in the medium reduced the SDBS removal rate of the O3/PAC system. This finding confirms that the presence of PAC during SDBS ozonation favours ozone transformation into .OH radicals. Comparison of the O3/PAC system with systems based on the use of O3 or O3/H2O2 showed that the efficacy of the O3/PAC system to remove SDBS is much greater than that of the traditional oxidation methods. Thus, in the first 5 min of treatment (usual hydraulic retention time), the percentage of SDBS removed was 18% and 30% for the O3 and O3/H2O2 systems, respectively, compared with 70% for the O3/PAC system. SDBS ozonation in surface waters intended for human consumption demonstrated that the O3/PAC approach is the most efficacious of the studied systems, considerably increasing the SDBS removal rate and also reducing the concentration of dissolved organic carbon. Therefore, the results of this study show that the system based on O3/PAC is a highly attractive option for the treatment of drinking water. 相似文献
4.
Formaldehyde is one of the most common indoor air pollutants in Chinese residences. This study introduces a novel laminated plate with adjustable surface temperature to remove gaseous formaldehyde. The plate is fabricated with activated carbon, polyimide, and copper foil via thermal compression. The plate can be regenerated in situ by applying a direct current to the copper foil. Adsorption‐regeneration cycle tests were conducted to evaluate the plate's formaldehyde removal performance. The overall removal efficiency of the fabricated laminated plate with glue mass fraction of 25% and thickness of 1.5 mm was about 30% at the face velocity of 0.8‐1.2 m/s. The pressure drop was about 5 Pa. Its removal ability can be regenerated in situ in 8 minutes by increasing the surface temperature to 80°C. The fabricated laminated plate showed good durability after 52 cycles of adsorption‐regeneration tests. The results indicate that the proposed laminated plate can enhance the purifying efficiency and enlarge the life span of ordinary, cheap sorbents. It makes cheap materials with low performance suitable for air purification. 相似文献