Into the photooxidation process, several factors such as pH, time of irradiation, dose of UV light, lamp power, contaminant concentration, turbidity of the solution and the presence of salts can interfere with the pho...Into the photooxidation process, several factors such as pH, time of irradiation, dose of UV light, lamp power, contaminant concentration, turbidity of the solution and the presence of salts can interfere with the photodegradation of pollutants. This research aims to evaluate the influence of salts： NaCl, MgCl2, CaCI2, BaC12, CuCl2, Na2SO4, MgSO4, MnSO4, FeSO4, CuSO4, Na3PO4, K2CrO4 and K2Cr207 in concentrations of 0.0005 M, 0.005 M and 0.05 M during photodegradation of aqueous solution of 59.5 mg/L of nitrobenzene at a pH of 2.5. It was observed that the presence of salts such as CuCI2, CuSO4, FeSO4, K2CrO4 and K2Cr207 interfere negatively in the system UV/H202 applied for degradation of nitrobenzene; possibly by oxidation of Fe2＋ to Fe3＋ and Cu＋ to Cu2＋ in the Cr case, due to the difficulty of transforming the Cr6＋ to Cr3＋ or because these solutions have color and act as radiation absorbing filter.展开更多
In several countries, the residual RHA （rice husk ash） has been produced in rice processing industries or in thermoelectric plants that use rice husk to generate heat and/or electrical energy, usually without burnin...In several countries, the residual RHA （rice husk ash） has been produced in rice processing industries or in thermoelectric plants that use rice husk to generate heat and/or electrical energy, usually without burning process control. This causes a reduction in the amorphous silica content of residual RHA, which distinguishes them from the RHA produced according to controlled burning process, which is totally amorphous and considered a highly reactive pozzolan. In this paper, the hydration products and the porous structure of binders paste were studied by replacing, in weight of 5%, 10% and 20% of Portland cement OPC （ordinary Portland cement）, by residual RHAs named A and B, which have high and low content of amorphous silica, respectively, using microstructure evaluation techniques as XRD （X-ray diffraction）, TG （thermogravimetric） tests and MIP （mercury intrusion porosimetry）. A reducing the size of the pores of the pastes was observed according to the increase of content replacement of RHA A and RHA B.展开更多
文摘Into the photooxidation process, several factors such as pH, time of irradiation, dose of UV light, lamp power, contaminant concentration, turbidity of the solution and the presence of salts can interfere with the photodegradation of pollutants. This research aims to evaluate the influence of salts： NaCl, MgCl2, CaCI2, BaC12, CuCl2, Na2SO4, MgSO4, MnSO4, FeSO4, CuSO4, Na3PO4, K2CrO4 and K2Cr207 in concentrations of 0.0005 M, 0.005 M and 0.05 M during photodegradation of aqueous solution of 59.5 mg/L of nitrobenzene at a pH of 2.5. It was observed that the presence of salts such as CuCI2, CuSO4, FeSO4, K2CrO4 and K2Cr207 interfere negatively in the system UV/H202 applied for degradation of nitrobenzene; possibly by oxidation of Fe2＋ to Fe3＋ and Cu＋ to Cu2＋ in the Cr case, due to the difficulty of transforming the Cr6＋ to Cr3＋ or because these solutions have color and act as radiation absorbing filter.
文摘In several countries, the residual RHA （rice husk ash） has been produced in rice processing industries or in thermoelectric plants that use rice husk to generate heat and/or electrical energy, usually without burning process control. This causes a reduction in the amorphous silica content of residual RHA, which distinguishes them from the RHA produced according to controlled burning process, which is totally amorphous and considered a highly reactive pozzolan. In this paper, the hydration products and the porous structure of binders paste were studied by replacing, in weight of 5%, 10% and 20% of Portland cement OPC （ordinary Portland cement）, by residual RHAs named A and B, which have high and low content of amorphous silica, respectively, using microstructure evaluation techniques as XRD （X-ray diffraction）, TG （thermogravimetric） tests and MIP （mercury intrusion porosimetry）. A reducing the size of the pores of the pastes was observed according to the increase of content replacement of RHA A and RHA B.
