Recovery of CaO from CaSO4 via CO reduction decomposition under different atmospheres.

CaSO4 reduction decomposition for CaO preparation provides a theoretical basis for the utilization of the industrial byproduct, gypsum. In this study, the effects of temperature (950 °C-1150 °C), CO2/CO partial-pressure ratio (1-15), CO concentration (1%-5%), and O2 concentration (1%-7%) on the preparation of CaO from CaSO4 by CO reduction decomposition under different reaction atmospheres were investigated. The physical properties of CaO prepared by the decomposition of CaSO4 and CaCO3 were analyzed and compared. Finally, the reaction mechanism of the reduction decomposition of CaSO4 to CaO by CO was studied. The findings reveal that CaSO4 can be completely decomposed into CaO when the reaction temperature exceeds 1000 °C, CO% ≥ 2%, and P(CO2)/P(CO) ≥ 8. Furthermore, the addition of an appropriate amount of O2 can improve the yield of CaO in the products. In an O2-CO-N2 atmosphere, where O2% = 7% and CO% = 16%, CaSO4 can be completely decomposed into CaO without the addition of CO2. The physical properties of CaO prepared by the reduction and decomposition of CaSO4 are better than those prepared by the calcination of CaCO3. An analysis of the reaction mechanism of the reduction decomposition of CaSO4 by CO reveals that CaSO4 generates CaO and CaS simultaneously. In addition, CaS can react with unreacted CaSO4 to form CaO. Furthermore, it can react with CO2 to produce CaO if an appropriate amount of CO2 is added to the reaction atmosphere. The secondary interactions of CaS with CaSO4 and CO2 can significantly improve the yield of CaO in the product.

Intensification of NO x Conversion over Activated Coke by Ozone Oxidation for Sintering Flue Gas at Low Temperatures.

Denitration (De-NO x ) over activated cokes (ACs) for sintering flue gas needs intensification. Gaseous reactions in a gas mixture containing NO, NO2, and NH3, with the effect of O2 concentration and moisture, were taken into consideration in the study of NO x conversion over ACs. Experimental studies on NO x conversion with and without NH3 over ACs were conducted using a fixed-bed reactor at 100 °C. The results demonstrated that moisture significantly affected NO x removal over ACs, especially the NO2 conversion. Under dry conditions, a disproportionation reaction of NO2 over ACs dominated NO x conversion with no NH3, whereas apparent fast selective catalytic reduction (SCR) over the ACs was observed in the presence of NH3. Regardless of the presence of absence of NH3 in wet mixtures, NO2 adsorption on ACs via the disproportionation route dominated the NO x conversion. Increasing the NO2/NO ratio in the simulated flue gas enhanced the NO x conversion rate over ACs. -C(ONO2) deposition on ACs generated by the disproportionation route inhibited NO x conversion with time. O3 oxidation was found to be efficient in increasing the NO2/NO ratio and intensifying the NO x conversion compared with commercially direct NH3-SCR over ACs. Increasing the temperature and decreasing the gas hourly space velocity can promote NO x conversion over ACs after O3 oxidation. NO oxidized with O3 coupled with NH3 spray and continuous regeneration of ACs is a potential method for removing NO x from sintering flue gas.

[Design and development of analysis software for acid-base balance disorder based on Visual Basic.NET].

OBJECTIVE: To develop a diagnostic analysis software for determining the type of acid-base balance disorder. METHODS: Mathematical models were built based on Henderson-Hasselbalch equations and compensation formulas, to determine the important parameters of acid-base balance disorder, and to develope acid-base balance disorder analysis process. The software was compiled using the Visual Basic.NET programming language, and the installation package was generated after debugging. Acid-base balance disorder cases were searched by PubMed, Wanfang and CNKI databases from 1980 to 2015, and the blood gas parameters [pH, arterial partial pressure of carbon dioxide (PaCO2), HCO3- and anion gap (AG)] and the types of acid-base imbalance (literature results) were recorded. All cases were reanalyzed by software and the type of acid-base balance disorder was determined (software diagnostic type). Kappa-test and McNemar-test were performed for the two diagnostic results. RESULTS: The "four parameters-four steps" analysis method was used as the analysis process to judge the types of acid-base balance disorder. "Four parameters" included pH, PaCO2, HCO3- and AG. "Four steps" were outlined by following aspects: (1) according to the pH, combined with PaCO2 and HCO3-, the primary types of acid-base balance disorder was determined; (2) according to the compensation situation, double mixed acid-base balance disorder (DABD) was determined; (3) according to AG value, three mixed acid-base disorders (TABD) were determined; (4) the ratio of ΔAG ↑ /ΔHCO3- ↓ was also calculated to determine whether there was normal AG metabolic acidosis or metabolic alkalosis. The software had the characteristics of simple interface, convenient operation, rapid judgment, and comprehensive analysis. It could judge all acid-base balance disorder types excepted "AG normal metabolic acidosis combined metabolic alkalosis". The software was used to reanalyze 112 cases of acid-base balance disorder reported in the literature, with a consistent rate of 87.50% and better consistency of the diagnostic results (Kappa test: κ = 0.84, P < 0.01; McNemar test: χ2 = 0.87, P = 0.65). CONCLUSIONS: The software can be used as an important tool to judge the type of acid-base balance disorder, and provide clinicians with diagnostic reference, which have practical value and application prospect.

Desorption of CO2, SO2, and NH3 in the vacuum evaporation of desulfurization wastewater.

Mechanical vapor compression and multi-effect evaporation have been widely used in achieving zero discharge of desulfurization wastewater as they are energy-saving and efficient technologies. Solubilized weak ions, such as CO32-, SO32-, and NH4+, in the desulfurization wastewater are partly converted into CO2, SO2, and NH3, respectively, during the vacuum evaporation process, thus affecting the heat exchange and compressor performance. In this study, the migration and coupling mechanism of CO2, SO2, and NH3 desorption in desulfurized wastewater under vacuum evaporation were analyzed. The effects of temperature, pressure, reaction time, and other factors on the migration process were discussed. The hydrolysis and electrolytic equilibrium constants of the related ions were obtained for temperatures between 70 and 90 °C. The results demonstrate the relationship between the desorption capacities of CO2, SO2, and NH3 and the hydrolysis constants of their respective ions. The desorption of CO2 and NH3 increased significantly when CO32- and NH4+ coexisted, whereas the SO2 desorption capacity remained low under the same experimental conditions. The experimental results indicate that the desorption of CO2, SO2, and NH3 is controlled by chemical reactions and can be described by first-order reaction kinetics.

Study on sulfur migration in activated carbon adsorption-desorption cycle: Effect of alkali/alkaline earth metals.

Activated carbon (AC) has been widely used in the removal of SO2 from flue gas owing to its well-developed pore structure and abundant functional groups. Herein, the effect of alkali/alkaline earth metals on sulfur migration was investigated based on the dynamic adsorption and temperature programmed desorption experiment. The adsorption and desorption properties of six types of AC (three commercial and three laboratory-made) were carried out on a fixed-bed experimental device, and the physical and chemical properties of samples were determined by X-ray fluorescence, X-ray diffraction, scanning electron microscopy/energy dispersive X-ray, and X-ray photoelectron spectroscopy analysis. The experimental results showed that the adsorbed SO2 cannot be completely desorbed by increasing the regeneration temperature (350 - 850°C), while the SO2 fixed in the AC combines with the Ca-based minerals in the ash to form a stable sulfate. For different samples, higher ash content, higher CaO content in the ash and a more developed pore structure lead to a higher SO2 fixation rate. Moreover, the multiple adsorption-desorption cycles experiment showed that the effect of SO2 fixation is mainly reflected in the first cycle, after which the adsorption and desorption amount are approximately the same. This study elucidates the effect of alkali/alkaline earth metals on the adsorption-desorption cycle of AC, which provides a deeper understanding of sulfur migration in the AC flue gas desulfurization process.

Synergistic Cascade Carrier Extraction via Dual Interfacial Positioning of Ambipolar Black Phosphorene for High-Efficiency Perovskite Solar Cells.

2D black phosphorene (BP) carries a stellar set of physical properties such as conveniently tunable bandgap and extremely high ambipolar carrier mobility for optoelectronic devices. Herein, the judicious design and positioning of BP with tailored thickness as dual-functional nanomaterials to concurrently enhance carrier extraction at both electron transport layer/perovskite and perovskite/hole transport layer interfaces for high-efficiency and stable perovskite solar cells is reported. The synergy of favorable band energy alignment and concerted cascade interfacial carrier extraction, rendered by concurrent positioning of BP, delivered a progressively enhanced power conversion efficiency of 19.83% from 16.95% (BP-free). Investigation into interfacial engineering further reveals enhanced light absorption and reduced trap density for improved photovoltaic performance with BP incorporation. This work demonstrates the appealing characteristic of rational implementation of BP as dual-functional transport material for a diversity of optoelectronic devices, including photodetectors, sensors, light-emitting diodes, etc.

Effects of temperature, oxygen and steam on pore structure characteristics of coconut husk activated carbon powders prepared by one-step rapid pyrolysis activation process.

Activated carbon powders made from coconut husk (CHCs) were prepared by one-step rapid pyrolysis activation process. Effects of temperature, oxygen and steam on the pore structure of CHCs were investigated. Results showed that high temperature, oxygen and steam all motivated the development of the CHCs pore structure. High temperature accelerated the evaporation of volatiles and led to more micropore structures. Oxygen promoted the development of both micropores and mesopores. CHCs' porosity separately presented a linear and a logarithmic growth with the increase of the preparation temperature and oxygen content. CHCs prepared under 1000 â„ƒ with activation agents of 6% oxygen and 20% steam exhibited the largest specific surface area and total pore volume of 415.85 m2/g and 0.1748 cm3/g. Steam can diffuse into the CHC matrix and enhance the formation of more mesopores. Steam over 20% would over-burn the substance and lead to the collapse of some pore structures.

A novel on-site wheat straw pretreatment method: Enclosed torrefaction.

In this study, a novel on-site torrefaction method was proposed for the pretreatment of wheat straw, in which the wheat straw was placed in an enclosed environment for torrefaction. The effects of different torrefaction conditions on the properties of both solid and gaseous products were investigated. When the temperature of enclosed torrefaction increased from 200 °C to 250 °C, the higher heating value, fixed carbon and C content of wheat straw increased by 12.7%, 80.3% and 18.1%, respectively, and the moisture decreased by 25.0%. Enclosed torrefaction causes more mass loss due to the smoldering of wheat straw, and a strong decomposition of the hemicellulose of wheat straw during the torrefaction process. The gaseous products obtained by enclosed torrefaction have fewer acids and more esters than conventional torrefaction. Compared with conventional torrefaction, enclosed torrefaction performs similarly, or even better, in improving the properties of wheat straw.

Fe-rich biomass derived char for microwave-assisted methane reforming with carbon dioxide.

Microwave-assisted methane reforming with carbon dioxide was dealt with in this work, using a Fe-rich biomass-derived char by one-step preparation. The main factors on the reforming reaction and stability of this catalyst were evaluated, together with a series of characterization on the produced gas and the used char. The char obtained from biomass pyrolysis with Fe2O3 addition of 10% exhibited the best performance on dry reforming reaction. A target CH4 conversion of 95% over this char was realized at 800 °C. Moreover, H2/CO ratio achieved with this char was prone to approach the stoichiometric value. Compared to CO2 conversion, CH4 conversion was more promoted with the increase of CO2/CH4 ratio. The variation of CO2/CH4 ratio also leaded to a noticeable changes on H2/CO ratio. More importantly, the selected char presented a satisfied stability, evidenced by the total decrease of 4.8% for CH4 conversion and 3.1% for CO2 conversion in the test of 160 min. This was contributed to a depressed in-situ carbon consumption and a moderate deterioration of porous structure. Gaseous products obtained with the appropriate char in a long run had a syngas content of 88.79% and H2/CO ratio of 0.92 on average.

Exothermic laws applicable to the degradation of o-phenylenediamine in wastewater via a Fe3+/H2O2 homogeneous quasi-Fenton system.

We studied the exothermic laws of Fe3+/H2O2 homogeneous quasi-Fenton degradation of o-phenylenediamine in waste water, and analyzed the effects of [H2O2] and [Fe3+], initial reaction temperature, and other factors on the solution temperature elevation (Δt), temperature elevation duration (T), and chemical oxygen demand degradation rate (η) during the degradation of the target pollutant. Our study found that [H2O2] is a major factor affecting Δt, while [Fe3+] and t 0 are the main factors influencing the exothermic reaction rate. For the conditions wherein [H2O2] is 0.2 mol L-1, [Fe3+] is 10 mmol L-1, pH = 7.8, initial reaction temperature is 30 °C, and reaction duration is 30 min, Δt of 200 mL of 0.04 mol L-1 o-phenylenediamine is 7.2 °C and η is 93.45%. The exothermic reaction between the free radicals (·OH and ) and o-phenylenediamine and the exothermic reaction due to auto-consumption of free radicals are the main reasons for the increased temperature of the solution.

IR and kinetic study of sewage sludge combustion at different oxygen concentrations.

Thermal degradation of sewage sludge disposal is attracting more attention due to the increase in municipal wastewater treatment. In this work the performance of the thermochemical processes of sewage sludge at different oxygen concentrations was investigated by thermogravimetric (TG) and Fourier transform infrared analysis (FTIR) study. The oxygen concentrations were varied systematically from 0 to 20%, representing heating process from pyrolysis to full combustion. The evolutions of surface functional groups in these processes were also investigated by in situ diffuse reflectance infrared Fourier transform spectra (DRIFT), which helped to understand the reaction mechanism during the thermal degradation, especially when the reaction conditions were different. The heating process was divided into four stages, dehydration (below 200 °C), devolatilization (200-400 °C), char combustion (above 400 °C), and secondary devolatilization (above 650 °C). Reaction mechanism and kinetic model was proposed based on the stages of heating process. Oxygen concentration was presented explicitly in the reactions and kinetic equations. The model was then developed for the heating processes at different oxygen concentrations, followed by fittings of kinetic parameters. Some of the parameters in the model were fixed as constants to minimize the number of variations. The fitted model agreed well with the TG curves at different oxygen concentrations and could illustrate the evolution of intermediates and products during the heating process. The developed kinetic model could be further applied for the modeling of sewage sludge pellets combustion considering oxygen diffusion process.

Non-isothermal TGA study on the combustion reaction kinetics and mechanism of low-rank coal char.

In this paper, the combustion reaction kinetics of pyrolysis char of low-rank coal is studied by thermal analysis technology. For the combustion process of the char at different heating rates, the reaction kinetic parameters were calculated by three common mode-free methods (FWO method, KAS method and Starink method); the reaction model was determined by Malek method and Popescu method. Research shows that activation energy E α of char combustion calculated by the three methods was 110.66-70.31 kJ mol-1, 104.35-59.60 kJ mol-1 and 104.34-59.99 kJ mol-1, respectively, and the activation energy decreased with increasing conversion rates. There is a compensation effect between the activation energy and pre-exponential factor of char combustion. Results of the kinetic analysis by Malek method and Popescu method both indicated that the Avrami-Erofeev equation (n = 3/2) (f(α) = 3/2(1 - α)[-ln(1 - α)]1/3) controlled by nucleation and nuclei growth models is the most probable reaction model of char combustion.

Influence of offset angle of mid-secondary air nozzles on gas-particle flow characteristics in a furnace.

A three-component particle-dynamics anemometer was used to measure the characteristics of two-phase gas-particle flows in a primary air nozzle using a gas/particle two-phase test facility. The jet trajectory of primary air velocities, Reynolds stress and particle concentration profiles were obtained. Based on this, the advantages and disadvantages of increasing the offset angle were analyzed to optimize performance. The results show that gas-particle slippage is not noticeable in the furnace, even though the mid-secondary air offset angle changes. Within the jet's free developing zone, the location of the peak concentration does not change with the mid-secondary air offset angles. Properly enlarging the offset angle of mid-secondary air nozzles will delay the mixing of the secondary air into the primary-air-and-coal mixture and realize horizontal-staged combustion in a furnace. It also can enhance the stability of airflow and form a better blended jet tail, meanwhile reducing the vortex at the back-fire side and avoiding a short circuiting of the airflow. It is favorable for increasing combustion efficiency and preventing slagging and high-temperature corrosion.

NO x reduction by CO over ASC catalysts in a simulated rotary reactor: effect of CO2, H2O and SO2.

The influence of CO2, H2O and SO2 on the NO reduction by CO over Fe/Co activated semi-coke catalyst was investigated in a simulated rotary reactor. The results showed that, in the simulated rotary reactor, the influence of CO2 and H2O on the NO adsorption was significant at low temperatures, and the inhibition became weak when increasing the temperature. However, the NO adsorption efficiency could not be improved by increasing temperature after catalyst sulfur poisoning. The heavily inhibited NO adsorption process, which was due to the competitive adsorption and formation of the sulfate, resulted in a low NO reduction efficiency in the presence of CO2, H2O or SO2. The in situ DRIFT study showed that the dominant effect of CO2, H2O and SO2 on the NO adsorption was the inhibition of the free nitrate ions formation. In addition, the introduction of CO2, H2O and SO2 could not change the route of NO reduction, but just reduced the degree of the NO + CO reduction.

The low-temperature corrosion characteristics of alcohol-based fuel combustion.

In this paper, the low-temperature corrosion characteristics of the four fuel combustions that include methanol, diesel, MF75 (the volume fraction of methanol is 75 ± 2%), and MF50 (the volume fraction of methanol is 50 ± 2%) were studied. MF75 and MF50 were modulated by methanol, diesel and a small amount of cosolvent. The quality indicators of four fuels were judged by the specific standard. The acid dew point temperature of the four kinds of fuel combustion flue gas was calculated and compared, and the acid ion in the condensate of the four fuel combustion products was analyzed and tested. Based on this method, the corrosiveness of four kinds of condensate was determined. The corrosion rates of five metals (brass, 304 stainless steel, 316 stainless steel, corten steel, and Q245 steel) were tested by two different methods (electrochemistry corrosion and static immersion corrosion). The experimental results show that the quality indicators of four fuels have all reached the relevant national standards. The dew point temperature of methanol, MF75 and MF50 are lower than that of diesel. The corrosion products on the surface of corten steel are relatively compact and easily accumulate dust, which is not conducive to the safe operation of the boiler. The corrosion resistance properties of 316 stainless steel is excellent, showing that it would be the ideal material choice for the low-temperature zone of a boiler flue.

[Disposable nursing applicator-pocket of indwelling central venous catheter].

Catheter related infection is the most common complication of central venous catheter, which pathogen mainly originate from the pipe joint and the skin around puncture site. How to prevent catheter infection is an important issue in clinical nursing. The utility model disclosed a "disposable nursing applicator-pocket of indwelling central venous catheter", which is mainly used for the fixation and the protection. The main structure consists of two parts, one is medical applicator to protect the skin around puncture site, and the other is gauze pocket to protect the catheter external connector. When in use, the catheter connector is fitted into the pocket, and then the applicator is applied to cover the puncture point of the skin. Integrated design of medical applicator and gauze pocket was designed to realize double functions of fixation and protection. The disposable nursing applicator-pocket is made of medical absorbent gauze (outer layer) and non-woven fabric (inner layer), which has the characteristics of comfortable, breathable, dust filtered, bacteria filtered, waterproof, antiperspirant and anti-pollution. The utility model has the advantages of simple structure, low cost, simple operation, effective protection, easy realization and popularization.

[Procedural analysis of acid-base balance disorder: case serials in 4 patents].

OBJECTIVE: To establish the standardization process of acid-base balance analysis, analyze cases of acid-base balance disorder with the aid of acid-base balance coordinate graph. METHODS: The acid-base balance theory were reviewed systematically on recent research progress, and the important concepts, definitions, formulas, parameters, regularity and inference in the analysis of acid-base balance were studied. The analysis of acid-base balance disordered processes and steps were figured. The application of acid-base balance coordinate graph in the cases was introduced. RESULTS: The method of "four parameters-four steps" analysis was put forward to analyze the acid-base balance disorders completely. "Four parameters" included pH, arterial partial pressure of carbon dioxide (PaCO2), HCO3- and anion gap (AG). "Four steps" were outlined by following aspects: (1) according to the pH, PaCO2 and HCO3-, the primary or main types of acid-base balance disorder was determined; (2) primary or main types of acid-base disorder were used to choose the appropriate compensation formula and to determine the presence of double mixed acid-base balance disorder; (3) the primary acid-base balance disorders were divided into two parts: respiratory acidosis or respiratory alkalosis, at the same time, the potential HCO3- should be calculated, the measured HCO3- should be replaced with potential HCO3-, to determine whether there were three mixed acid-base disorders; (4) based on the above analysis the data judged as the simple AG increased-metabolic acidosis was needed to be further analyzed. The ratio of ΔAG↑/ΔHCO3-↓ was also needed to be calculated, to determine whether there was normal AG metabolic acidosis or metabolic alkalosis. In the clinical practice, PaCO2 (as the abscissa) and HCO3- (as the ordinate) were used to establish a rectangular coordinate system, through origin (0, 0) and coordinate point (40, 24) could be a straight line, and all points on the straight line pH were equal to 7.40. The acid-base balance coordinate graph could be divided into seven areas by three straight lines [namely pH = 7.40 isoline, PaCO2 = 40 mmHg (1 mmHg = 0.133 kPa) line and HCO3- = 24 mmol/L line]: main respiratory alkalosis area, main metabolic alkalosis area, respiratory + metabolic alkalosis area, main respiratory acidosis area, main metabolic acidosis area, respiratory + metabolic acidosis area and normal area. It was easier to determine the type of acid-base balance disorders by identifying the location of the (PaCO2, HCO3-) or (PaCO2, potential HCO3-) point on the acid-base balance coordinate graph. CONCLUSIONS: "Four parameters-four steps" method is systematic and comprehensive. At the same time, by using the acid-base balance coordinate graph, it is simpler to estimate the types of acid-base balance disorders. It is worthy of popularizing and generalizing.

Pyrolysis of tyre powder using microwave thermogravimetric analysis: Effect of microwave power.

The pyrolytic characteristics of tyre powder treated under different microwave powers (300, 500, and 700 W) were studied via microwave thermogravimetric analysis. The product yields at different power levels were studied, along with comparative analysis of microwave pyrolysis and conventional pyrolysis. The feedstock underwent preheating, intense pyrolysis, and final pyrolysis in sequence. The main and secondary weight loss peaks observed during the intense pyrolysis stage were attributed to the decomposition of natural rubbers and synthetic rubbers, respectively. The total mass loss rates, bulk temperatures, and maximum temperatures were distinctively higher at higher powers. However, the maximum mass loss rate (0.005 s-1), the highest yields of liquid product (53%), and the minimum yields of residual solid samples (43.83%) were obtained at 500 W. Compared with conventional pyrolysis, microwave pyrolysis exhibited significantly different behaviour with faster reaction rates, which can decrease the decomposition temperatures of both natural and synthetic rubber by approximately 110 °C-140 °C.

Study on the effects of soluble microbial product on phosphate adsorption onto fresh hydrous ferric oxides by surface complexation models.

As one of the major soluble organic compounds in membrane bioreactors, soluble microbial product (SMP) can combine the surface sites on hydrous ferric oxides (HFO), which can compete with HFO for the uptake of phosphate. In this study, SMP was extracted from an MBR plant with long-term stable operation, and the effects of SMP on phosphate adsorption onto fresh HFO (FHFO) were investigated at pH values of 6.0 and 7.8 in a two-phase system composed of FHFO (solid phase) and SMP/phosphate (liquid phase). The phosphate adsorption capacity of FHFO was found to decrease significantly with increase in the pH value and SMP concentration. A diffuse layer model (DLM) and a charge distribution multisite complexation (CD-MUSIC) model, which take these factors into account, were developed to describe the speciation of SMP and phosphate on FHFO surface. Both of the models provided good description of phosphate adsorption behavior in the presence of SMP at different pH. The equilibrium constants of surface complexation reactions between SMP and HFO were obtained by inversion calculation as log10K = 15.1 ± 0.11 in DLM model and log10K = 12.1 ± 0.5 in CD-MUSIC model, which can improve the equilibrium constants database of surface complexation models.

Effects of Lowering Dialysate Calcium Concentration on Carotid Intima-Media Thickness and Aortic Stiffness in Patients Undergoing Maintenance Hemodialysis: A Prospective Study.

BACKGROUND AND AIM: The study aimed to prospectively evaluate the effects of lowering the dialysate calcium concentration (DCa) to 1.25 mmol/l on Chinese patients undergoing maintenance hemodialysis (MHD), which are largely unknown to date. METHODS: A singer-center, prospective, randomized trial was conducted for 2 years. The DCa in one group was decreased from 1.5 to 1.25 mmol/l but there was no change in the other group. The clinical outcomes, biochemical parameters, medicine treatments and markers of vascular change were compared among the 2 groups at different time intervals. RESULTS: At baseline, the groups were similar with respect to serum levels of calcium, phosphorus, intact parathyroid hormone and fibroblast growth factor-23 as well as carotid intima-media thickness (cIMT) and carotid-femoral pulse wave velocity (cf-PWV). It was found that the serum phosphorus concentration in the lower DCa group had decreased markedly at 2-year follow-up (0-month: 7.13 ± 1.56 mg/dl; 24-month: 5.92 ± 1.73 mg/dl; p = 0.005). Serum calcium (p = 0.018), cIMT (p = 0.029) and cf-PWV (p = 0.024) in DCa 1.25 group were significantly lower than those in 1.5 group at the 24-month visit. Kaplan-Meier curve revealed that patients in DCa 1.25 group had a better rate of survival. In the multivariate Cox regression analysis, cIMT (HR 1.010; 95% CI 1.002-1.217; p = 0.015) and cf-PWV (HR 1.265; 95% CI 1.022-1.567; p = 0.031) were potential risk factors for mortality in those patients. Importantly, we showed that the average change in these 2 risk variables were both associated with the average change in levels of serum calcium and phosphorus. CONCLUSION: Our results indicate that lowering DCa to 1.25 mmol/l may be suitable for the MHD patients in our unit.