Daqiang Cang

The properties of ZnO nanofluids and the role of H2O2 in the disinfection activity against Escherichia coli

This work investigates the disinfection property of ZnO nanofluids, focusing on H2O2 production and the disinfection activities of ZnO suspensions with different particles/aggregates. The possible disinfection mechanisms of ZnO suspensions are analysed. In this work, a medium mill was used to produce ZnO suspensions with different sizes of particles/aggregates. During the milling process, five ZnO suspension samples (A-E) were produced. X-ray Diffraction (XRD) and Dynamic Light Scattering (DLS) analyses revealed that after milling, the size of ZnO particles/aggregates in the suspensions decreased. Disinfection tests, H2O2 detection assays and fluorescent analyses were used to explore the disinfection activities and mechanism of ZnO suspensions. Disinfection tests results showed that all the produced ZnO suspension exhibited disinfection activity against Escherichia coli. ZnO suspensions with smaller particles/aggregates showed better disinfection activities. The presence of H2O2 in ZnO suspension was analysed. The H2O2 detection assay suggested that there is 1 μM H2O2 in 0.2 g/l ZnO Sample A, while there was no H2O2 present in ZnO Sample E. Though results showed that there was no H2O2 present in ZnO Sample E, Sample E with a size of 93 nm showed the best disinfection activities. Fluorescence tests detected that the interaction between E. coli lipid vesicles and ZnO Sample E was much faster and more efficient. This study firstly demonstrated that ZnO suspensions with different particles/aggregates produced different amount of H2O2. Results suggested that H2O2 is responsible for the disinfection activity of larger ZnO particles/aggregates while the interaction between smaller ZnO particles/aggregates and vesicle lipids is responsible for the disinfection activity of smaller ZnO particles/aggregates.

Synthesis of steel slag ceramics： chemical composition and crystalline phases of raw materials

Two types of porcelain tiles with steel slag as the main raw material (steel slag ceramics) were synthesized based on the CaO-Al2O3-SiO2 and CaO-MgO-SiO2 systems, and their bending strengths up to 53.47 MPa and 99.84 MPa, respectively, were obtained. The presence of anorthite, α-quartz, magnetite, and pyroxene crystals (augite and diopside) in the steel slag ceramics were very different from the composition of traditional ceramics. X-ray diffraction (XRD) and electron probe X-ray microanalysis (EPMA) results illustrated that the addition of steel slag reduced the temperature of extensive liquid generation and further decreased the firing temperature. The considerable contents of glass-modifying oxide liquids with rather low viscosities at high temperature in the steel slag ceramic adobes promoted element diffusion and crystallization. The results of this study demonstrated a new approach for extensive and effective recycling of steel slag.

Effects of sintering atmosphere on the physical and mechanical properties of modified BOF slag glass

This study proposes an efficient way to utilize all the chemical components of the basic oxygen furnace (BOF) slag to prepare high value-added glass-ceramics. A molten modified BOF slag was converted from the melting BOF slag by reducing it and separating out iron component in it, and the modified BOF slag was then quenched in water to form glasses with different basicities. The glasses were subsequently sintered in the temperature range of 600–1000°C in air or nitrogen atmosphere for 1 h. The effects of different atmospheres on the physical and mechanical properties of sintered samples were studied by using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) and by conducting experiment on evaluating the sintering shrinkage, water absorption and bulk density. It is found that the kinetics of the sintering process is significantly affected by sintering atmosphere. In particular, compared with sintering in air atmosphere, sintering in N2 atmosphere promotes the synergistic growth of pyroxene and melilite crystalline phases, which can contribute to better mechanical properties and denser microstructure.

Strength and consolidation mechanism of iron ore and coal pellets

Abstract The consolidation mechanisms of green and metallised iron ore and coal pellets (ICPs) using four kinds of inorganic binders and four organic binders were studied. The strength of wet ICPs mainly depends on capillary force. However, that of preheated ICPs mainly depends on chemical adsorption, followed by viscous force. The metallised pellet strength can be controlled as per the growth and spread of the iron joined crystals, and the strength of the metallised pellets increases with the iron crystal area. The adhesive properties of phenolic resin as a binder are significantly better than those of other binders, and it does not affect ICP reduction. With 2% phenolic resin, the compressive strength and drop strength of preheated ICPs improved to 312·5 N and by 15·1 times respectively, whereas the metallisation degree and compressive strength of metallised ICPs improved to 92·56% and 3505 N respectively (at 1473 K).

Reduction characteristics and kinetics of iron oxide by carbon in biomass

The characteristics and kinetics of iron oxide reduction by carbon in biomass composites were studied. Iron oxide can be reduced by biomass very rapidly, and the degree of metallisation and reduction increases with temperature. Iron oxide reduction by carbon in biomass can be divided into two stages: reduction by volatile carbon followed by reduction by non-volatile carbon. The reduction times of the two stages both decrease with increasing temperature. The first reduction is controlled by gas diffusion, whereas the second stage is dominated by carbon gasification.

Staged reaction kinetics and characteristics of iron oxide direct reduction by carbon

Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction (XRD), and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by isoconversional (model-free) methods. Three stages in the reduction are Fe2O3→Fe3O4, Fe3O4→FeO, and FeO→Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO2 content in the Fe2O3→Fe3O4 stage but is substantially greater than the CO2 contents in the Fe3O4→FeO and FeO→Fe stages, where gasification starts at approximately 1205 K. The activation energy (E) of the three stages are 126–309 kJ/mol, 628 kJ/mol, and 648 kJ/mol, respectively. The restrictive step of the total reduction is FeO→Fe. If the rate of the total reduction is to be improved, the rate of the FeO→Fe reduction should be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and FexOy reduction by CO, which are the restrictive step in the last two stages, require further study.

Antimicroorganism activities comparison among ZnO, TiO 2 , MgO and SiO 2 nanoparticles suspensions at different pH values

This work investigated the antimicroorganism activities of ZnO, TiO2, MgO and SiO2 nanoparticles suspensions at different pH values. In this work, E. coli was used as model bacteria to test the antimicroorganism activities of these nanoparticles suspensions. Growth curves investigation with and without these nanoparticles suspensions was used to examine the antimicroorganism activities. The results demonstrate that ZnO and TiO2 suspensions have an inhibiting effect against the growth of E. coli bacterial cells at all pH levels. MgO suspensions have a weak or no antibacterial activity at a pH value of 5, but have some extent of promoting effect at pH 7 and 11. SiO2 suspensions have very little effect on the growth of E. coli bacterial cells at all pH values. One of the reasons for the difference of antimicroorganism activities among these nanoparticles suspensions at different pH values may be related to the electrostatic forces between nanoparticles and bacterial cells.

Enhanced antimicrobial activity of ZnO nanofluids in sonophotocatalysis and its mechanism

This study investigated the inactivation efficiency of ZnO nanofluids against E. coli in sonophotocatalysis with the aeration of nitrogen, oxygen, argon and their mixtures. The results showed that inactivation efficiency was increased when aeration was combined with sonophotocatalysis. Addition of different types of gases could lead to the different inactivation efficiency. The inactivation efficiencies were shown in the following order: no aeration < nitrogen < argon < oxygen < Ar/O2(3:7) < Ar/O2(7:3) < Ar/O2(5:5). The production of hydroxyl radicals was explored to understand the inactivation mechanism. Compared with sonophotocatalysis without aeration, more hydroxyl radicals were produced in sonophotocatalysis with aeration, which could lead to changes of cellular substances. Furthermore, characterization of E. coli cells using Raman spectroscopy and FTIR illustrated that sonophotocalysis could affect the cellular substances containing carbohydrates, proteins and P containing molecules. Results suggested that the enhanced antimicrobial activity with aeration was originated from stronger cavitational activity, together with the formation of hydroxyl radicals. Compared to sonophotocatalysis without aeration, more dissolved oxygen was existed in sonophotocatalysis with aeration, which could enhance the formation of hydroxyl radicals.

Effects of Fe 2 O 3 on the properties of ceramics from steel slag

Ferric oxide is one of the key factors affecting both the microstructure and the properties of CaO-MgO-SiO2-based ceramics. Research on this effect is significant in the utilization of iron-rich solid wastes in ceramics. Ceramic samples with various Fe2O3 contents (0wt%, 5wt%, and 10wt%) were prepared and the corresponding physical properties and microstructure were studied. The results indicated that Fe2O3 not only played a fluxing role, but also promoted the formation of crystals. Ceramics with 5wt% of Fe2O3 addition attained the best mechanical properties with a flexural strength of 132.9 MPa. Iron ions were dissolved into diopside, consequently causing phase transformation from diopside and protoenstatite to augite, thereby contributing to the enhancement of its properties. An excess amount of Fe2O3 addition (10wt% or more) resulted in deteriorated properties due to the generation of an excess volume of liquid and the formation of high-porosity structures within ceramics.

Complementation in the composition of steel slag and red mud for preparation of novel ceramics

A method for preparing novel ceramics was developed in this study. Different ratios red muds were added to steel slags to optimize the preparation of novel ceramics by a traditional ceramic preparation process. The sintering mechanism, microstructure, and performance were studied by X-ray diffraction techniques, scanning electron microscopy, and combined experiments of linear shrinkage, water absorption, and flexural strength. The results confirmed that red mud can reduce the volumetric instabilities through the complementarity of red mud and ferroalloy slag. The crystal phases in the ceramics are all pyroxene group minerals, including diopside ferrian, augite, and diopside. The flexural strength of the ceramic that contains 40wt% red mud and was prepared at the optimal sintering temperature (1140°C) is greater than 93 MPa; its corresponding water absorption is less than 0.05%.