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In this study, a polyphosphate superplasticizer (PPE) used in sulphoaluminate cement was synthesized by using un-saturated phosphate ester as monomer. The effects of molecular structures of polyphosphate superplasticizer on the fluidity of sulphoaluminate cement paste were investigated. When n (HPEG) :n (MOEP) :n (TGA) :n (APS) was 1:4:0.2:0.1, the effect of PPE on the fluidity and fluidity retention of sulphoaluminate cement is better compared to ordinary polycarboxylate superplasticizer (PCE). The mechanism of polyphosphate superplasticizer was probed in detail by X-ray photoelectron spectroscopy (XPS). The results showed that after adding 1% polyphosphate superplasticizer, the peaks of Ca2p and Al2p of sulphoaluminate cement shifted 0.173 eV and 0.175 eV respectively, which were greater than those of ordinary polycarboxylate superplasticizer. Accordingly, this new type of polyphosphate superplasticizer synthesized by us can play its role in dispersing sulphoaluminate cement particles via strong chemisorption on their surfaces. [ABSTRACT FROM AUTHOR]

The mechanism of deactivation of MnO x /TiO 2 is studied. The MnO x /TiO 2 catalyst prepared by co-precipitation method has poor stability, the NO conversion decreased to about 50% after 100 h denitrification. Catalyst activity and physicochemical properties of the catalyst before and after SCR denitrification were compared and analyzed through BET, XRD, SEM, which indicated that dispersion of active sites and surface area of catalyst were decreased after 100 h denitrification. Catalyst activity and surface chemical compositions were investigated by XPS, H 2 -TPR, NH 3 -TPD, which shown that content of Mn3+ and chemisorbed oxygen on the surface decreases. The different active sites of catalyst and adsorption characteristics of reacting gases (NH 3 and NO) over catalyst before and after denitrification was investigated through in-situ DRIFT. It was found that NO is more easily adsorbed on the surface of catalyst than NH 3 and form nitrate. The nitrate that did not participate in the reaction gradually accumulate on the surface of the catalyst, which inhibits the adsorption of NH 3. This is the main reason for the deactivation of the catalyst. Unlabelled Image • The long-term stability of the Mn/TiO 2 catalyst was studied. • Comparing the differences in the catalytic activity and physicochemical properties of fresh and used catalyst. • Showing the atomic-scale insights into mechanism of deactivation for Mn/TiO 2 catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Design a method based on DFT calculations to study the modification of the manganese-based catalyst. • Explain the reason why MnO 2 doped by different element show different sulfur resistance. • Unravel the catalytic property of MnO 2 doped by different element on NH 3 -SCR. Modification of manganese-based selective catalytic reduction (SCR) catalyst by five kinds of the element was studied to improve its SO 2 resistance. In this paper, density functional theory (DFT) calculation was used to analyze the effects of doped atom on electronic dispersion and crystal structure of MnO 2 (100). Our result demonstrated that the doping of Ni, Cr, and Co could increase the strength of Lewis acid sites for the manganese-based catalyst, while Se and Sn decrease that. On the other hand, the manganese-based catalyst modified by Se and Sn present better resistance to sulfur poisoning. By comparing the dissociation energy barrier of NH 3 over different element doped catalyst and analyzing the partial density of state (PDOS) for SO 2 adsorbed on the catalyst, we found that Cr could be as a potential dopant modifying the manganese catalyst, because of it could convert sulfur to Brønsted acid sites which catalyze NH 3 -SCR through followed the LH-mechanism. [ABSTRACT FROM AUTHOR]

A superhydrophilic poly (ethyleneimine)/poly (acrylicacid) PEI/PAA-Cerium carbonate (Ce 2 (CO 3 ) 3 ) composite membrane was fabricated through layer-by-layer (LbL) self-assembly and in-situ mineralization of Ce 2 (CO 3 ) 3 . The surface structures, wetting behavior and NF performance of the membranes were investigated. The results indicated that the water contact angle of [PEI/PAA-Ce 2 (CO 3 )] 3.0 membrane decreased with increasing incorporated Ce 2 (CO 3 ) 3 content. Under 0.025 mol/L of Ce 2 (CO 3 ) 3 content, the prepared membrane showed superhydrophilic surface with water contact angle of 3.1 ° , which can effectively separate methyl blue, xylenol orange and eriochrome black T from aqueous solution with rejection of more than 95% and flux of more than 152.0 L/m 2 MPa h, respectively. In addition, the superhydrophilic membrane showed better long-term running stability, and antifouling property. After 3 cycle of running and cleaning, the flux recovery rate was about 85%, and the irreversible flux decay rate was 14.53%. Moreover, the Derjaguin Landau Verwey Overbeek (XDLVO) approach further demonstrated that the superhydrophilic membrane showed higher antifouling property than the hydrophilic one. [ABSTRACT FROM AUTHOR]

Mn/TiO 2 catalysts has been shown excellent selective catalyst reduction (SCR) activity at low temperature. However, the exhaust gases in some plant contained alkali metal compounds after dust removal, which showed a serious poisoning effect on activity of Mn/TiO 2 catalyst. Our previous work showed that the poisoning effect of potassium on catalyst was most serious among these alkali elements. In the study, in situ diffuse reflectance infrared transform spectroscopy (DRIFT) and density function theory plus dispersion (DFT-D) calculation were used to investigate the mechanism how the potassium species have a negative impact on Mn/TiO 2 catalytic. The results indicated that there were two reasons for that alkali metal elements make the Mn/TiO 2 catalyst inactive. The first one is that the amount of NH 3 adsorption was on the Lewis acid sites, which was main active substances for the reduction of NO. The second one is that the electrons tend to occupy high energy states under effect of potassium, which resulted in decrease of oxidative capacity of catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] The reaction mechanism of selective catalytic reduction of NO with ammonia (SCR) on MnO x /TiO 2 catalysts was investigated through experiments and density functional theory (DFT) calculation. Firstly, the catalytic performance of catalyst with different molar ratios of MnO x /TiO 2 was investigated and then was analyzed by NH 3 temperature programmed desorption (NH 3 -TPD). The crystalline structure and the valence state of the MnO x /TiO 2 catalyst were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). According to the results, the model of MnO x /TiO 2 was established. Secondly, the different active sites of catalyst surface and adsorption characteristics of reacting gases during the SCR reaction based on in-situ DRIFT was investigated. Finally, the energy of different elemental reaction and isomerization of intermediate was calculated by MS Dmol3. It was found that the main active substance of catalyst was Mn4+ species which distributed dispersedly on the catalyst surface. The introduction of MnO x dopant can promote the adsorption of gas and reduce the formation energy of oxygen vacancy. The complete catalytic cycle goes in three steps: (a) Lewis acid site reaction follows Eley-Rideal mechanism; (b) Brønsted acid site reaction follows Langmuir-Hinshelwood mechanism; (c) Regeneration of catalyst. [ABSTRACT FROM AUTHOR]

In this study, the effect of CO2 concentration on carbonation depth, semi-carbonated zone, pore size distribution and carbonation products in concrete were investigated. The CO2 concentration was increased from 0.035 % to 2 % and 20 % at 70 % relative humidity and 20 °C. The results show that the carbonation process of 2 % CO2 was more similar to natural carbonation than 20 % CO2, as evidenced by the better linearity fitness of carbonation depth. The length of semi-carbonated zone was 6 mm at 2 % CO2 and 8 mm at 20 % CO2 within 16 weeks, a number that cannot be ignored when predicting the service life of concrete under carbonation. CH remained in a small amount in the completely carbonated zone instead of being completely consumed, and CH consumed at 20 % CO2 is about 1.5-2.0 times that of 2 % CO2. The content of CaCO3 in the completely carbonated zone at 20 % CO2 was higher than that of 2 % CO2. CaCO3 could fill in large pores between hydration products, so the porosity, average pore size and aperture decreased with CO2 concentration. [ABSTRACT FROM AUTHOR]

Mn-Ni/TiO2catalysts were prepared using a joint precipitation method with acid-dissolved titanium slag as raw material for selective catalytic reduction of nitrogen oxide. The joint precipitation method was accomplished with different precipitants, such as sodium hydroxide, carbamide, ammonia, or hydrogen peroxide. The deNOx activities of the catalysts prepared by different precipitants were investigated with SCR activity reactor within temperatures of 90–350°C. It is evident that the Mn-Ni/TiO2catalyst with carbamide-ammonia-hydrogen peroxide as precipitant has superior catalytic activity, which the NO conversion can reach 90% at 120°C, with a wider temperature window (120–300°C) for the NH3-SCR reaction. H2-TPR results showed that the reduction potential of MnOx species on Mn-Ni/TiO2catalysts is increased compared to that of Mn/TiO2catalysts. Oxygen mobility is enhanced by interaction between Ni and Mn atoms due to use of carbamide-ammonia peroxide as precipitant. XPS results suggest that the presence of MnO2is the major phase in nickel-doped Mn/TiO2catalysts. Our NH3-TPD results illustrated that the catalysts have a lot of acid-active sites, which lead to attracting more ammonia to participate in the catalytic reaction. [ABSTRACT FROM AUTHOR]