Abstract
2-methylisoborneol (2-MIB) is a common taste and odor compound caused by off-flavor secondary metabolites, which represents one of the greatest challenges for drinking water utilities worldwide. A TiO2-coated activated carbon (TiO2/PAC) has been synthesized using the sol-gel method. A new TiO2/PAC photocatalyst has been successfully employed in photodegradation of 2-MIB under UV light irradiation. In addition, the combined results of XRD, SEM-EDX, FTIR and UV-Vis suggested that the nano-TiO2 had been successfully loaded on the surface of PAC. Experimental results of 2-MIB removal indicated that the adsorption capacities of PAC for 2-MIB were higher than that of TiO2/PAC. However, in the natural organic matter (NOM) bearing water, the removal efficiency of 2-MIB by TiO2/PAC and PAC were 97.8% and 65.4%, respectively, under UV light irradiation. Moreover, it was shown that the presence of NOMs had a distinct effect on the removal of MIB by TiO2/PAC and PAC. In addition, a simplified equivalent background compound (SEBC) model could not only be used to describe the competitive adsorption of MIB and NOM, but also represent the photocatalytic process. In comparison to other related studies, there are a few novel composite photocatalysts that could efficiently and rapidly remove MIB by the combination of adsorption and photocatalysis.
Highlights
The taste and odor (T&O) compounds are produced as off-flavor secondary metabolites by three primary taxa: (1) cyanobacteria, (2) actinobacteria and (3) fungi [1], and occur in up to 50% of lake/reservoir waters in China [2]
The objectives of this study were to (i) prepare a nano-composite (TiO2 /powdered activated carbon (PAC)) to degrade 2-MIB under UV light irradiation; (ii) investigate the adsorption characteristics of 2-MIB based on the adsorption and photo-catalytic degradation kinetics, as well as equilibrium adsorption isotherms; (iii) evaluate the impacts of natural organic matter (NOM) on the adsorption; (iv) establish a simplified model used for well understanding the relationship between removal efficiency of 2-MIB and the dosages of photocatalysts
11.99 wt % of Ti in the energy-dispersive X-ray spectroscopy (EDX) spectrum was very close to the content of TiO2 (10% wt) in TiO2 /PAC, further indicating that nano-TiO2 was successfully scattered on the surface of PAC (Figure 1d)
Summary
The taste and odor (T&O) compounds are produced as off-flavor secondary metabolites by three primary taxa: (1) cyanobacteria, (2) actinobacteria and (3) fungi [1], and occur in up to 50% of lake/reservoir waters in China [2]. These T&O compounds have historically been related to algal blooms that occur in the summer or early fall, when water temperatures are at their highest (about 20 °C). The presence of natural organic matter (NOM > 3 mg/L) leads to a reduction in the adsorption capacity of PAC due to biofilm formation on the adsorbent [16]. Research on the influences of NOM on the environmental behavior of adsorbent have been carried out but with limited studies [17]
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