Stratified control of chemical crystallization in a pellet fluidized bed for pH-Adjusted fluoride and phosphate reduction: An experimental study.

Chemical crystallization granulation in a fluidized bed offers an environmentally friendly technology with significant promise for fluoride removal. This study investigates the impact of stratified pH control in a crystallization granulation fluidized bed for the removal of fluoride and phosphate on a pilot scale. The results indicate that using dolomite as a seed crystal, employing sodium dihydrogen phosphate (SDP) and calcium chloride as crystallizing agents, and controlling the molar ratio n(F):n(P):n(Ca) = 1:5:10 with an upflow velocity of 7.52 m/h, effectively removes fluoride and phosphate. Stratified pH control-maintaining weakly acidic conditions (pH = 6-7) at the bottom and weakly alkaline conditions (pH = 7-8) at the top-facilitates the induction of fluoroapatite (FAP) and calcium phosphate crystallization. This approach reduces groundwater fluoride levels from 9.5 mg/L to 0.2-0.6 mg/L and phosphate levels to 0.1-0.2 mg/L. Particle size analysis, scanning electron microscopy-energy-dispersive X-ray spectroscopy, and X-ray diffraction physical characterizations reveal significant differences in crystal morphology between the top and bottom layers, with the lower layer primarily generating high-purity FAP crystals. Further analysis shows that dolomite-induced FAP crystallization offers distinct advantages. SDP not only dissolves on the dolomite surface to provide active sites for crystallization but also, under weakly acidic conditions, renders both dolomite and FAP surfaces negatively charged. This allows for the effective adsorption of PO43-, HPO42-, and F- anions onto the crystal surfaces. This study provides supporting data for the removal of fluoride from groundwater through induced FAP crystallization in a chemical crystallization pellet fluidized bed.

Induced crystallization for the simultaneous removal of hardness-iron-manganese in groundwater: An experimental study.

Hardness, iron, and manganese are common groundwater pollutants, that frequently surpass the established discharge standard concentrations. They can be effectively removed, however, through induced crystallization. This study has investigated the effectiveness of the simultaneous removal of hardness-iron-manganese and the crystallization kinetics of calcium carbonate during co-crystallization using an automatic potentiometric titrator. The impacts pH, dissolved oxygen (DO), and ion concentration on the removal efficiency of iron and manganese and their influence on calcium carbonate induced crystallization were assessed. The results suggest that pH exerts the most significant influence during the removal of hardness, iron, and manganese, followed by DO, and then the concentration of iron and manganese ions. The rate of calcium carbonate crystallization increased with pH, stabilizing at a maximum of 10-10 m/s. Iron and manganese can be reduced from an initial level of 4 mg/L to <0.3 mg/L and 0.1 mg/L, respectively. The removal rate of iron, however, was notably higher than that of manganese. The DO concentration correlates positively with the removal of iron and manganese but has minimal impact on the calcium carbonate crystallization process. During the removal of iron and manganese, competitive interactions occur with the substrate, as increases in the concentration of one ion will inhibit the removal rate of the other. Characterization of post-reaction particles and mechanistic analysis reveals that calcium is removed through the crystallization of CaCO3, while most iron is removed through precipitation as Fe2O3 and FeOOH. Manganese is removed via two mechanisms, crystallization of manganese oxide (MnO2/Mn2O3) and precipitation. Overall, this research studies the removal efficiency of coexisting ions, the crystallization rate of calcium carbonate, and the mechanism of simultaneous removal, and provides valuable data to aid in the development of new removal techniques for coexisting ions.

Preparation of Iron-Based Catalysts by Mechanical Solid-Phase Ball Milling and Their Applications in Cohydrogenation of Coal and Petrochemical Coking Residual Oil.

Catalysts are an important factor in reducing harsh reaction conditions and increasing oil yields for the cohydrogenation of coal-oil. In this article, nano-iron-based catalysts have been prepared by mechanical solid-phase ball milling with FeCl3·6H2O, Fe(NO3)3·9H2O, and ammonium carbonate as reactants. The catalysts were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. With these catalysts, cohydrogenation behaviors of coal-oil have been carried out with Hami Baishihu coal and Karamay petrochemical coking residual oil under conditions of 400 °C, initial pressure of 7 MPa, and reaction time of 1 h. The results showed that the coal conversion rate reached 98.45% and the oil yield reached 77.73% when the catalyst prepared with FeCl3·6H2O as an iron source was added. Compared with research results reported in the literature, under the same conditions, the catalyst prepared in this article showed better catalytic activity in the cohydrogenation of coal-petrochemical coking residual oil.

Review of Molybdenum Disulfide Research in Slurry Bed Heavy Oil Hydrogenation.

With the growing demand for gasoline and diesel fuel and the shortage of conventional oil reserves, there has been extensive interest in upgrading technologies for unconventional feedstocks such as heavy oil. Slurry bed reactors with high tolerance to heavy oil have been extensively investigated. Among them, dispersive MoS2 is favored for its excellent hydrogenation ability for heavy oil even under harsh reaction conditions such as high pressure and high temperature, its ability to effectively prevent damage to equipment from deposited coke, and its ability to meet the requirement of high catalyst dispersion for slurry bed reactors. This paper reviews the relationship between the structure and hydrogenation effectiveness of dispersive molybdenum disulfide, the hydrogenation mechanism, and the improvement of its hydrogenation performance by adding defects and compares the application of molybdenum disulfide in heavy oil hydrogenation, desulfurization, deoxygenation, and denitrification. It is found that the current research on dispersive molybdenum disulfide catalysts focuses mostly on the reduction of stacking layers and catalytic performance, and there is a lack of research on the lateral dimensions, microdomain regions, and defect sites of MoS2 catalysts. The relationship between catalyst structure and hydrogenation effect also lags far behind the application of MoS2 in the precipitation of hydrogen, etc. Oil-soluble and water-soluble MoS2 catalysts eventually need to be converted to a solid sulfide state to have hydrogenation activity. The conversion history of soluble catalysts to solid-type catalysts and the key to their improved catalytic effectiveness remain unclear.

[Development of a chemiluminescent enzyme immunoassay for the detection of bisphenol A in milk].

OBJECTIVE: To develop an indirect competitive chemiluminescent enzyme immunoassay( CLEIA) for the detection of bisphenol A in milk samples. METHODS: The CLEIA conditions including antigen coated concentration, concentration of methanol, concentration of enzyme labeled anti-antibody, p H and ionic strength were optimized to build competitive inhibition curve, determine the linear range and detection limit, and study the recovery of spiked milk samples. RESULTS: In the standard curve of the optimized CLEIA, the half maximal inhibitory concentration( IC_(50)) was 3. 95 ng/m L and the limit of detection( LOD) was 0. 66 ng/m L. The CLEIA showed good recoveries with spiked milk ranging from 95. 0%-112. 9% with the relative standard deviation of0. 93%-3. 96%. CONCLUSION: The proposed method has a high sensitivity and good specificity and is suitable for the determination of bisphenol A in milk samples.