Calcium Sulfate Solution Research Articles

Comparing Calcium Sulfate Fouling on Polymeric and Metal Heat Transfer Surfaces

AbstractFouling mitigation provides many challenges in process equipment, especially in heat exchangers. In this work, the fouling behaviors of two polymers are compared to 1.4301 stainless steel (SS) in calcium sulfate solutions. An experimental setup that allows to classify the materials quickly and under varying process conditions is used to determine the fouling behavior. Results are compared to a screening apparatus which can test up to three materials simultaneously. Finally, the cleaning behavior of all three materials is investigated. Results show that polyether ether ketone (PEEK) is superior to SS in mitigating fouling and is easier to clean; however, polyether ether ketone with 30 % talcum (TKT) is not. This is attributed to the surface roughness of the materials.

Integration of seeding-induced crystallization with microbubble aeration for membrane fouling and wetting control in vacuum membrane distillation

In this work, a bench-scale vacuum membrane distillation crystallization (VMDC) system coupled with microbubble aeration (MBA) was developed for treating high-salinity feed brine. Herein, the effect of seeding dose on membrane fouling and wetting control in the VMDC system was studied by using synthetic saturated calcium sulfate solution. The results showed that introducing gypsum seeds at a dose of 0.5 g/L effectively restricted membrane fouling and wetting. Subsequently, seeding-induced crystallization coupled with MBA was employed to investigate the control effect on membrane fouling and wetting during VMDC with simulated high-salinity feed brine treatment. As 0.5 g/L gypsum seeds were directly added at 7 h in the VMDC experiment while employing MBA, membrane fouling and wetting were effectively controlled. Finally, the mechanism behind the control of membrane fouling and wetting was elucidated during VMDC operation by integrating seeding-induced crystallization with MBA. This could be ascribed to the synergic effect of gypsum seeds and microbubbles in bulk solution. In brief, this work offers a promising approach to control membrane fouling and wetting during concentrating high-salinity wastewater by VMD.

65 Testing the effects of rigid encapsulations on bovine primordial follicle quiescence versus growth

OBJECTIVES/GOALS: There is an interest in developing a bioprosthetic ovary for ovarian tissue transplantation. The properties of the ovarian extracellular matrix need to be better understood in order to replicate the human ovary. We tested the effects of an encapsulating hydrogel at different rigidities on bovine primordial follicle activation, growth, and survival. METHODS/STUDY POPULATION: Bovine primordial follicles were isolated from ovarian cortex. A mean of 9.9 follicles (range 3-24) were encapsulated per bead in either 1% or 5 % alginate across 4 experiments. The encapsulated follicles were subsequently crosslinked in a calcium sulfate solution. Follicles were then cultured for 8 days with light microscopy imaging taken every other day along with media exchanges. Follicles were then examined using immunofluorescence. Growth and survival curves were constructed and all statistical analyses were performed using Graph Pad Prism 9. RESULTS/ANTICIPATED RESULTS: A total of 372 follicles were encapsulated across 32 beads (16 in 1% alginate and 16 in 5% alginate). There were no differences in initial follicle size between the two conditions (33.53 µm vs. 32.45 µm, p=0.47). At the end of 8 days, there was no difference between follicle size (59.55 vs. 56.06, p=0.48). Additionally, there was no difference in survival between 1% and 5% alginate encapsulation (57.75% vs. 52.43%. p=0.40). Immunofluorescence is being performed on encapsulated follicles to confirm the presence of DDX4, a molecular marker of oocytes, after 8 days in culture. Additional encapsulated follicles have also been submitted for histologic sectioning and hematoxylin and eosin staining to better characterize the viability and health of these follicles after 8 days in culture. DISCUSSION/SIGNIFICANCE: There was no significant difference in growth or survival between primordial follicles cultured in 1% or 5% alginate gels. Immunofluorescent analysis confirmed the presence of viable follicles at the end of 8 days of culture. Future work needs to further explore how factors in the ovarian extracellular matrix impact follicle maintenance and growth.

Precipitation behavior of calcium sulfate in leach solution of ion-adsorption rare earth ore after reverse osmosis

Ion-adsorption rare earth ore (IAREO) is a crucial source of mid-heavy rare earths elements (M-HRE). Reverse osmosis technology is a promising technique for the pre-concentration of the leach solution from in-situ leaching of IAREO. However, calcium sulfate scaling is inevitably formed in sulfate system, causing decreases in the flux and life time of membrane. Herein, to simulate the precipitation behavior of calcium sulfate in the leach solution of IAREO during reverse osmosis, a series of experiments was conducted in binary and quaternary supersaturated calcium sulfate solution systems. Experimental data show that the concentration of Ca2+ decreases with the increase of the concentration of Mg2+, and increases with the increase of the concentration of RE3+ in both binary and quaternary systems. Whereas, the influence of Al3+ on the concentration of Ca2+ is different. This variation of the Ca2+ concentration is explained by thermodynamic analysis. The difference of association concentration for Mg2+, Al3+ and RE3+ with SO42− in binary or quaternary system is the main reason. Finally, the influence and mechanisms of antiscalant on the precipitation behavior of calcium sulfate are discussed. X-ray diffraction (XRD), Zeta potential and scanning electron microscopy (SEM) analyses reveal that polyacrylic acid (PAA) effectively inhibits the crystal growth of calcium sulfate, and the precipitation time of calcium sulfate is prolonged, indicating that PPA is a potential inhibitor for calcium sulfate scaling during the process of reverse osmosis.

Experimental investigation of surface roughness/wettability pattern effect on crystallization fouling over falling-film flow

In many industries, including desalination, scaling in heat exchangers is a persistent issue, and most methods of scaling control involve environmentally hazardous chemical additives. Exploiting the effects of surface features and flow-imposed shear on salt deposition might introduce a new approach to scale management, opening the possibility of self-cleaning surfaces. In this work, we experimentally explore surface roughness and wettability patterns interaction with salt deposition and flow shear. Heat transfer and scale mass deposition on flat surfaces are measured during thin-film evaporation of calcium sulfate solution. A wide range of surface roughness (0.027–2.66 μm) is studied at fixed flow and heat flux conditions. Due to improved mixing, heat transfer is enhanced with rougher surfaces initially; however, degrades more quickly than smoother surfaces. Following a period of initial mass deposition fluctuation, a steady scaling stage is observed, with rough surfaces scaling more than smooth surfaces. Wettability patterned surfaces can suppress crystal nucleation without sacrificing overall surface wetting, resulting in antifouling performance and heat transfer enhancement. Scale mass deposition on a patterned surface is reduced by 60 %, and 27 % heat transfer improvement over the baseline surface is found. This study provides guidance to surface manipulation for heat transfer improvement and fouling mitigation.

Anisotropic gypsum scaling of corrugated polyvinylidene fluoride hydrophobic membrane in direct contact membrane distillation

Membrane distillation (MD) technology has gained a lot of attention for treatment of geothermal brine, high salinity waste streams. However, mineral scaling remains a major challenge when treating complex high-salt brines. The development of surface-patterned superhydrophobic membranes is one of the core strategies to solve this problem. We prepared flat sheet membranes (F-PVDF) and hydrophobic membranes with micron-scale corrugated pattern (C-PVDF) using a phase separation method. Their scaling behavior was systematically evaluated using calcium sulfate solutions and the impact of the feed flow was innovatively investigated. Although C-PVDF shows higher contact angle and lower sliding angle than F-PVDF, the scaling resistance of C-PVDF in the perpendicular flow direction has worst scaling resistance. Although the nucleation barrier of the corrugated membrane is the same at both parallel and perpendicular flow directions based on the traditional thermodynamic nucleation theory, experimental observations show that the C-PVDF has the best scaling resistance in the parallel flow direction. A 3D computational fluid dynamics (CFD) model was used and the hydrodynamic state of the pattern membranes was assessed as a determinant of the scaling resistance. The corrugated membrane with parallel flow mode (flow direction in parallel to the corrugation ridge) induces higher fluid velocity within the channel, which mitigated the deposition of crystals. While in the perpendicular flow mode (flow direction in perpendicular to the corrugation ridge), the solutions confined in the corrugated grooves due to vortex shielding, which aggravates the scaling. These results shed light on the mechanism of scaling resistance of corrugated membranes from a hydrodynamic perspective and reveal the mechanism of anisotropy exhibited by corrugated membranes in MD.

Effect of polyaspartic acid on the setting time and mechanical properties of α-hemihydrate gypsum

Polyaspartic acid (PASP) was an environment-friendly and biodegradable polymer, with a protein-like structure composed of L-aspartic acid residues. In this work, PASP with different molecular weights (2000, 4000–5000 and 6000–8000) was utilized as the retarder for α-hemihydrate gypsum (α-HH), and the effect of PASP on the coagulation, hydration and crystallization process of gypsum were investigated. Results showed that the addition of PASP with a low dosage of 0.01% efficiently delayed the hydration of α-HH and prolonged the setting process. Among three polyaspartic acids, PASP with molecular weight of 4000–5000 (PASP 4–5) exhibited the best performance not only in postponing the setting time to 95 min, but also in decreasing the negative impact of retarder on the strength of gypsum. Significantly, the slightest loss of 2.65% in compressive strength was obtained here when compared with other retarders previously reported, under the lowest dosage of 0.01% PASP 4–5. Consequently, the effect of PASP chain length on the retardation of α-HH was analyzed in detail. The conductivity, heat of hydration, X-ray diffraction (XRD), EDTA titration method and scanning electron microscopy (SEM) characterization found that PASP prevented the dissolution of α-HH. Total organic carbon analyzer (TOC) and X-ray photoelectron spectroscopy (XPS) measurements showed that the carboxyl groups of PASP adsorbed on the surface of α-HH to hinder the dissolution of α-HH. The molecular dynamic simulation of PASP further exhibited that three kinds of PASPs presented different conformations in supersaturated calcium sulfate solution due to the interaction between PASP and Ca2+ ions, and affected their solvent accessible surface area (SASA). In particular PASP 4–5 exhibited the smallest SASA and the strongest interaction with Ca2+ ions, causing the longest setting time of α-HH.

Evaluation of correlated studies using liquid cell and cryo-transmission electron microscopy: Hydration of calcium sulphate and the phase transformation pathways of bassanite to gypsum.

Insight into the nucleation, growth and phase transformations of calcium sulphate could improve the performance of construction materials, reduce scaling in industrial processes and aid understanding of its formation in the natural environment. Recent studies have suggested that the calcium sulphate pseudo polymorph, gypsum (CaSO4 ·2H2 O) can form in aqueous solution via a bassanite (CaSO4 ·0.5H2 O) intermediate. Some in situ experimental work has also suggested that the transformation of bassanite to gypsum can occur through an oriented assembly mechanism. In this work, we have exploited liquid cell transmission electron microscopy (LCTEM) to study the transformation of bassanite to gypsum in an undersaturated aqueous solution of calcium sulphate. This was benchmarked against cryogenic TEM (cryo-TEM) studies to validate internally the data obtained from the two microscopy techniques. When coupled with Raman spectroscopy, the real-time data generated by LCTEM, and structural data obtained from cryo-TEM show that bassanite can transform to gypsum via more than one pathway, the predominant one being dissolution/reprecipitation. Comparisons between LCTEM and cryo-TEM also show that the transformation is slower within the confined region of the liquid cell as compared to a bulk solution. This work highlights the important role of a correlated microscopy approach for the study of dynamic processes such as crystallisation from solution if we are to extract true mechanistic understanding.

Temperature-dependent dynamic fouling on superhydrophobic and slippery nonwetting copper surfaces

• Presents, for the first time, temperature-dependent dynamic fouling on nonwetting surfaces. • Elucidates, for the first time, effects of texturing method and surface type on fouling behavior. • Nonwetting surfaces show up to 75% less scaling compared to regular surfaces. • Electrodeposited surfaces offer better scaling resistance compared to etched surfaces. • Presents Hill-Langmuir model, for the first time, to describe the time evolution of scaling. Bioinspired, superhydrophobic and slippery liquid infused surfaces that offer nonwetting characteristics have been explored in recent years for fouling mitigation. However, most of the studies are in the context of biofouling or under static immersion at ambient temperature conditions that are not reflective of the dynamic flow environment in practice. This article presents, for the first time, a systematic study of dynamic fouling of superhydrophobic (SHS) and slippery lubricant-infused surfaces (LIS) over a range of flow and temperature conditions. Copper metallic surfaces were textured via electrodeposition or etching and further functionalized to achieve SHS and, additionally, infiltrated with a lubricant to fabricate LIS. The nonwetting surfaces were studied for their fouling behavior in a rotating Couette flow of a supersaturated calcium sulfate solution at different rotational speed and temperature. Fouling mineral mass accumulation on the different surfaces was measured as a function of time over a period of days using inductively coupled plasma mass spectroscopy and the fouled surfaces were investigated using scanning electron microscopy. Both SHS and LIS showed superior anti-scaling performance at all ranges of variables. An analytical Hill-Langmuir model is presented, for the first time, to describe the time evolution of scaling within 20% accuracy over the range of parameters studied. The study is the first to juxtapose two surface texturing methods, electrodeposition and etching, and two nonwetting surface types, SHS and LIS, subject to a common suite of experiments to elucidate fundamental understanding of mineral fouling on nonwetting surfaces.

Влияние натриевой соли карбоксиметилцеллюлозы и хлорида натрия на осаждение сульфата кальция из его пересыщенных растворов

The crystallization of gypsum from supersaturated solutions in dependence on the molar [Ca2+] : [SO42−] ratio 0,26 : 0,15 and 0,35 : 0,15 in the presence of the sodium carboxymethylcellulose (CMC, with the degree of polym- erization of 1000 units) and NaCl was investigated at 25C. The efficiency of inhibition was estimated from measure- ments of change in Ca2+ concentration during the precipitation process. It was found that increasing the calcium ions content in solution compared to sulfate ions results in decrease in the induction period of crystallization. At a polymer concentration of 1,0 g/L and sodium chloride concentration of 0,7 mol/l the induction period of gypsum crystallisation in a supersaturation of the calcium sulfate solution with the molar rate of [Ca2+] : [SO42−] of 0,35 : 0,15 increases from several minutes to one hour. Further increasing the sodium chloride concentration up to 2,0mol/l did not result in change in the induction period of crystallization. This enables the preparation of supersaturated calcium chloride solu- tions using brines for the sealing of porous rocks, cracks, and joints of soil formations.The results of the phase analysis confirmed that salt precipitates in the form of gypsum.

Analysis of the influence of different types of cement on the resistance to attack by sulfates

The diversity of the types of cement manufactured, driven by the extensive use of additions, has given cementitious composites properties that can directly interfere in the durability and useful life of concrete. Considering the interaction of sulfate ions with cement hydration products, in order to understand it becomes essential for the proper choice of materials in order to protect the structures from this aggressor agent. In order to verify the influence of the choice of cement type on the resistance to attack by sulfates, this article analyzes the compressive strength; sulfate content, electron microscopy and energy dispersive spectroscopy of mortars made with cements CP II-F-32, CP IV-32 and CP V-ARI submitted to calcium, sodium and magnesium sulfate solutions for 4 months. The specimens exposed to calcium and sodium sulfate solutions showed increased compressive strength at early ages due to the formation of ettringite in the pores. On the other hand, CP II-F-32 cement showed the greatest deterioration due to magnesium sulfate attack.

Investigation of Crystallization Fouling on Novel Polymer Composite Heat Exchanger Tubes

Metals are common construction materials for heat exchangers. However, metals may suffer from failure due to corrosion, especially in harsh environments. Innovative thermally conductive polymer composite tubes based on polypropylene or polyphenylene sulfide filled with graphite have been developed. Crystallization fouling on metal surfaces has been extensively studied. However, fouling data for polymer surfaces are very limited. In the current study, a stirred vessel test rig and a horizontal tube falling film test rig were used to compare the fouling propensity of the polymer composite tubes and common stainless steel tubes. Experiments were performed with calcium sulfate solutions and mixed salt solutions containing calcium carbonate and calcium sulfate. The induction periods and the fouling resistances over time were measured. The novel polymer composite tubes showed a lower crystallization fouling propensity compared to the stainless steel tubes. The induction period was longer and the reduction of the overall heat transfer coefficient over time was notably lower compared to the metal tubes.

Comparison of calcium scaling in direct contact membrane distillation (DCMD) and nanofiltration (NF)

Calcium scaling is commonly encountered in membrane separation processes with a profound impact on permeate flux and energy efficiency of these processes. Direct contact membrane distillation (DCMD) and nanofiltration (NF) were selected to study calcium scaling impact on thermal and pressure driven membrane processes. Calcium sulfate (CaSO4) and calcium carbonate (CaCO3) solutions with salinity in the range from 3000 to 30,000 mg/L were used as the feed. All DCMD and NF tests were performed at identical feed temperature (i.e., 40 °C) and shear conditions (i.e., Re = 771 ± 28). The average size of CaSO4 and CaCO3 crystals formed in the DCMD system was larger and the scale was more porous than in the NF system. The permeate flux in NF system was impacted by both calcium scales regardless of the feed salinity, while only CaSO4 scale formed at low salinity affected the performance of DCMD system. Surface crystallization in NF systems is likely extended into the membrane pores, which lead to permanent reduction in membrane permeability. This study demonstrated that the impact of calcium scaling is affected by both feed salinity and separation driving force, and is much less severe in thermal than pressure driven membrane processes.

Enhancing anti-scaling resistances of aromatic polyamide reverse osmosis membranes using a new natural materials inhibitor

The anti-scaling properties of green additive seeds were used as a novel environmentally friendly on the precipitation of calcium sulfate (gypsum) scale on the reverse osmosis (RO) in desalination plants. Initial screening of many additives included: Ginger extract, Pepper extract, Lysine, and Glutamic amino acid have been carried out. The effect of additives was evaluated by measuring calcium ions remained in the solution, and their performance that was comparable with the blank supersaturated calcium sulfate solution. The formation of the gypsum crystals has been verified using XRD and SEM analysis. It can be seen that the degree of inhibition of gypsum scale in the presence of these inhibitors is in the following order: Ginger extract > Pepper extract > Lysine > Glutamic at different concentrations (25,50,100 ppm). A concentration of 100 ppm Ginger extract led to be superior to others with an inhibition 98.80%. The SEM images of the collected precipitates when green inhibitors were added as a scale inhibitor, and were compared with that of the blank solution. The effect of Ginger extract (gypsum) scaling on selected reverse osmosis (RO) membrane surfaces was observed in the extent of surface scale coverage and surface crystal size among the membrane studied.

Early and Long-Term Assessment of High-Performance Concrete Contained Nano-Silica Exposed to Sulfate Attack

This research aims to study the influence of using the Nano-silica in high-performance concrete subjected to external sulfate attack with different levels. Four concrete mixes were prepared by using two types of Portland cement: ordinary and sulfate resistant cement. From each mix, cubic concrete specimens were cast and subjected to different exposure conditions. The concrete cubes were immersed in sodium sulfate (Na2SO4), magnesium sulfate (MgSO4) and calcium sulfate (CaSO4) solutions with concentrations of (1.5, 10 and 15) %. The specimens were tested for compressive strength at (3, 7, 14, 28, 90, 180, 270, 365, and 545) days and the values of sulfate penetration in concrete samples were determined. It can be found from the results that high-performance concrete containing Nano-silica gave a relatively good sulfate resistance compared to the reference sample. Moreover, results indicated that the strength deterioration was reduced after incorporating nano-silica.

ВЛИЯНИЕ НАТРИЕВОЙ СОЛИ КАРБОКСИМЕТИЛЦЕЛЛЮЛОЗЫ И ХЛОРИДА НАТРИЯ НА ОСАЖДЕНИЕ ДИГИДРАТА СУЛЬФАТА КАЛЬЦИЯ

The inhibition of gypsum was investigated at 25C in aqueous 0,7 and 1,5 mol/l NaCl solutions by so- dium carboxymethylcellulose (CMC-1000, with the degree of polymerization of 1000 units).The efficiency of inhibition was estimated from measurements of the calcium concentration in the supersaturated calcium sulfate solutions (0,15 mol/l) during the precipitation process by the standard procedure of complexometric titration. It was observed that the presence of NaCl exhibits synergistic effect on the performance of CMC-1000. In the presence of CMC-1000 at 0,5 g/l inhibitor concentration and sodium chloride at 0,7 mol/l concentration induction time, preceding the formation of the gypsum, increases from 100 (without NaCl) to 630 min. Induction times at 0,1 g/l CMC-1000 and sodium chloride at 0,7 and 1,5 mol/l concentrations are 60 and 32 min respectively. The results of X- ray powder diffraction indicated that dihydrate calcium sulfate and sodium chloride present in solid phase.

Antiscaling 3D printed feed spacers via facile nanoparticle coating for membrane distillation

Surface modification of feed spacers rather than membranes may hold more merit as an antiscaling strategy in membrane distillation (MD), as it avoids compromising the functionality of MD membrane. In this work, an antiscaling polyamide 3D printed spacer was developed for MD. The surface of the printed spacer was coated with fluorinated silica (FS) nanoparticles synthesized via a sol-gel process. The sol-gel approach used to synthesize the FS nanoparticles is considered a convenient and easy approach for engineering the spacer's surface structure and roughness. The performance of the FS coated printed surface was evaluated against other coating materials of different chemical properties. The coated surfaces were characterized using water contact angle measurements, ATR-FTIR, Raman, FESEM-EDX, atomic force and 3D microscopes. The 3D printed surface's microscale roughness and hydrophobicity increased, while its surface-free energy decreased with FS nanoparticles coating. The antiscaling performance of uncoated and FS coated spacers was then assessed in a direct contact MD process, using a scale-inducing aqueous solution of calcium sulfate as its feed. The scalant (Ca2+) attachment on the FS coated spacer was 0.24 mg cm−2, 74% lower than on the uncoated 3D spacer (0.95 mg cm−2). Also, by using the antiscaling FS coated spacer, scaling on the membrane surface dropped by 60%. The predominant factors that helped minimize scaling with FS coating were microscale roughness-induced hydrophobicity and reduced surface-free energy that weakened the scalant 's interaction with the spacer surface.

Calcium sulfate whisker prepared by flue gas desulfurization gypsum: A physical–chemical coupling production process

In this paper, the solid waste desulfurization gypsum produced by coal-fired power plants was used as a raw material to prepare calcium sulfate whiskers with high application prospects. Calcium sulfate whiskers with uniform morphology and high aspect ratio can be prepared by hydrothermal method in sulfuric acid solution. A new process of desulfurization gypsum activated by high-energy grinding to reduce the reaction temperature and sulfuric acid concentration was developed. Through the comparison of product morphology, the best grinding time was determined to be 3.5 h. The mechanism of desulfurization gypsum through physical–chemical coupling to reduce energy consumption was clarified. The activation of desulfurization gypsum by grinding and the acidic environment provided by the sulfuric acid solution made the calcium sulfate solution reached rapid saturation and accelerated the nucleation rate. By calculating the conversion and crystallization rate of calcium sulfate whiskers, it was found that there were obvious “autocatalytic” kinetic characteristics during the crystallization process.

Effects of methanol on CaSO4 ion associated species in mixed solutions: Solvation dynamics and hydrogen bond bridging structure

Abstract In this work, the effects of methanol on the solvation dynamics and hydrogen bond bridging structure of CaSO4 in a series of methanol-water solutions were investigated based on molecular dynamics simulations and density functional theory calculations. Results show that methanol can play important roles in regulating solvation structure and hydration dynamics in calcium sulfate solution with different ratios of methanol over water. Some water molecules in the hydrogen bond (HB) bridging structure around the Ca-OS bond of a CaSO4 pair can be replaced by methanol molecules. A HB bridging structure of double solvents can be formed even in mixed solution with high molar fraction of methanol. Due to such a HB bridging structure of dual solvents, the complete dehydration of CaSO4 ion associated structures in the mixed solvents may be quite difficult during the ion aggregation process. Our results provide useful information for understanding the phase/polymorphism selection in CaSO4 solution.

Postharvest Calcium Salt Treatment of Fresh Jujube Fruit and its Effects on Biochemical Characteristics and Quality after Cold Storage

Abstract Jujube fruit quickly undergoes spoilage and normally has a short shelf life. Therefore, the effect of immersion treatment in different calcium salts on qualitative and biochemical characteristics of fresh jujube fruit was evaluated. Treatments included control (distilled water) and solutions of calcium chloride, calcium nitrate, and calcium sulfate at a concentration of 0.5 and 1%. Fruits were immersed in water or calcium salt solution for 5 min, air-dried and then cold stored at 4 °C for 50 days. The results showed that such treatment did not affect significantly the pulp color and the anthocyanin concentration in the fruit. However, the soluble solids in the treated fruits significantly decreased compared with the control. Interestingly, all levels of calcium salts, except 0.5% calcium nitrate, preserved the total antioxidant capacity in comparison with the control. Concentrations of 1% calcium nitrate, chloride, and sulfate significantly increased crispness compared with the control. The taste of fruit treated with calcium sulfate significantly deteriorated compared with the control and other treatments. In general, 1% calcium nitrate and 1% calcium chloride applied before storage preserved or strengthened the jujube fruit qualities after storage compared with control. It can be concluded that such treatment is recommended for practical application.