Fe 2 O 3 @CeO 2 nanocomposites were synthesized by water bath heating method to activate NaHSO 3 for Orange II dye (50 mg L −1 ) degradation, which reached up to 98.2% within 120 min. The Fe 2 O 3 @CeO 2 and NaHSO 3 dosages and the molar ratios of Ce and Fe in Fe 2 O 3 @CeO 2 were investigated to obtain the optimum conditions as follows: 0.02 g Fe 2 O@CeO 2 , 0.1 g NaHSO 3 and the molar ratio of Ce and Fe was 5:2 (designated as Ce-Fe-1, or simply Fe 2 O 3 @CeO 2 ). In addition, Fe 2 O 3 @CeO 2 catalyst displayed superior catalytic performance to those materials that were previously reported, as verified by the good stability (reached 90.9% after three cycles) and high degradation rate of Orange II (98.2%) of the currently developed material. Existence of · SO 4 – and · OH radicals were verified by Electron Spin Resonance Spectroscopy during degradation, and these radicals are proposed to have high degradation efficiency of Orange II. On the basis of the detected radicals, a possible degradation mechanism was proposed to provide more choices for the application of sulfite in advanced oxidation processes (AOPs).
A high nitrate concentration in scrubber water is a major factor that restricts ship applications of NOx wet absorption technology. In this paper, an absorption system (Na2SO3/NaHSO3) that can effectively improve NO2 absorption and reduce the concentrations of nitrate and nitrite was studied. Several factors that affect the NOx absorption efficiency and the concentrations of nitrate and nitrite were investigated in a bubble reactor by using Na2SO3 and Na2SO3/NaHSO3. In addition, the reaction mechanism for the process of NO2 absorption was deduced. The results illustrate that increases in S(IV) concentration and initial NO2 concentration could enhance the NOx absorption efficiency while increases in the NO/NO2 ratio and SO2 concentration decreased the NOx absorption efficiency. Moreover, the maximum NOx absorption efficiency was 97.8% at 0.15 mol/L S(IV) and 1400 ppm of NO2 when using the Na2SO3/NaHSO3 absorption system. The S(IV) concentration was the main factor affecting the NOx absorption efficiency and the concentrations of nitrate and nitrite. Increasing the SO2 concentration slightly affected the NOx absorption efficiency but was beneficial for decreasing the concentrations of nitrate and nitrite. The performance of the Na2SO3/NaHSO3 absorption system was better than that of Na2SO3 in the presence of oxygen. Furthermore, the minimum concentrations of nitrate and nitrite were 13.5 and 0 mg/L, respectively, in the Na2SO3/NaHSO3 absorption system for 1100 ppm of NO2 and 0.3 mol/L S(IV) and were much lower than current regulations for scrubber water. Finally, compared with other experimental results, the Na2SO3/NaHSO3 absorption system exhibits great potential for ship NOx wet absorption, and the addition of NaHSO3 plays a key role in decreasing the concentrations of nitrate and nitrite.
Bisulfite-activated permanganate oxidation (PM/BS) technology is an emerging oxidation process that can rapidly oxidize organic contaminants and degrade some permanganate-resistant organic contaminants. For the first time, the influences of PM/BS technology as a pre-oxidation process on the formation potentials of disinfection by-products (DBPFPs) during chlorination of humic acid (HA) solution and three natural water samples were investigated. The results revealed that PM/BS pre-oxidation only slightly affected the DBPFPs of HA in the absence of Br - although it changed the structure of HA according to the fluorescence characterization result. With the presence of Br - , PM/BS pre-oxidation enhanced the generation of trihalomethanes but inhibited that of nitrogenous DBPs (N-DBPs) during chlorination of HA. The toxic risk analysis showed that the toxicity of the generated DBPs from chlorinating HA solution without Br - only changed slightly after PM/BS pre-oxidation but it was decreased by 14% in the presence of 150 μg/L Br − due to PM/BS pre-oxidation. This should be associated with the inhibiting effect of PM/BS pre-oxidation on the generation of N-DBPs and several haloacetic acids in the presence of Br - . Because of the complex matrix of natural water samples, PM/BS pre-oxidation had minor influence on the amount and the potential toxicity of DBPs generated during chlorination. The above results suggested that PM/BS technology could be an alternative of the drinking water pretreatment.
Through precipitation polymerization approach, bovine serum albumin (BSA) molecularly imprinted polymer (MIP) was synthesized with various reagents to ascertain the optimal synthesis condition. The optimized synthesis condition is methacrylic acid (MAA) as functional monomer, N,N′-methylenebisacrylamide (MBA) as crosslinker, template molecular/functional monomer/initiator ratio of 1:6:3, and K2S2O8/NaHSO3 initiator ratio of 1:2. BSA adsorption by synthesized MIP conformed to second-order kinetic adsorption equation and Langmuir adsorption isotherm. The maximum adsorption amount of MIP was 106.2 mg/g. Moreover, when the lysozyme (LYZ) was introduced as interfering adsorbate, the separation factor was up to 3.09, indicating that the MIP has a high affinity towards BSA.
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