Reusing Flowback and Produced Water with Different Salinity to Prepare Guar Fracturing Fluid

Economical and environmental concerns have forced the oil and gas industry to consider reusing flowback and produced water for fracturing operations. The major challenge is that the high-salinity of flowback water usually prevents its compatibility with several fracturing fluid additives. In this paper, the authors explored an economic and effective method to prepare guar fracturing fluids with different salinity waters. The main research idea was to use chelating agents to mask metal ions, such as calcium and magnesium, that are harmful to crosslinking. Firstly, a complexometric titration test was conducted to measure the chelating ability of three chelating agents. Secondly, through viscosity, crosslinking, and hanging tests, it was verified that the complex masking method could cope with the problem of high-valence metal ions affecting crosslinking. Thirdly, the preferred chelating agent was mixed with several other additives, including thickeners, crosslinkers, and pH regulators, to prepare the novel guar fracturing fluid. The comprehensive performances of the novel fluid system were tested such as temperature and shear resistance, friction reduction, gel-breaking performance, and core damage rate. The results show that the organophosphate chelating agent (i.e., CA-5) had the greatest ability to chelate calcium and magnesium ions. There was a good linear relationship between the dosage of CA-5 and the total molar concentration of calcium and magnesium ions in brine water. The main mechanism was that the chelating agent formed a complex with calcium and magnesium ions at a chelation ratio of 1:5. The test results of the comprehensive performance evaluation indicate that the prepared guar fracturing fluid met the requirements for field application, and the lower the salinity of the flowback water, the more it is economical and effective.

Differences in the Effects of Calcium and Magnesium Ions on the Anammox Granular Properties to Alleviate Salinity Stress

Divalent cations were known to alleviate salinity stress on anammox bacteria. Understanding the mechanism of reducing the salinity stress on anammox granules is essential for the application of the anammox process for saline wastewater treatment. In this study, the effect of Ca2+ and Mg2+ augmentation on the recovery of the activity of freshwater anammox granules affected by salinity stress was evaluated. At the condition of a salinity stress of 5 g NaCl/L, the specific anammox activity (SAA) of the granule decreased to 50% of that of the SAA without NaCl treatment. Augmentation of Ca2+ at the optimum concentration of 200 mg/L increased the SAA up to 78% of the original activity, while the augmentation of Mg2+ at the optimum concentration of 70 mg/L increased the SAA up to 71%. EPS production in the granules was increased by the augmentation of divalent cations compared with the granules affected by salinity stress. In the soluble EPS, the ratio of protein to polysaccharides was higher in the granules augmented by Ca2+ than with Mg2+, and the functional groups of the EPS differed from each other. The amount of Na+ sequestered in the soluble EPS was increased by the augmentation of divalent cations, which seems to contribute to the alleviation of salinity stress. Ca. Kuenenia-like anammox bacteria, which were known to be salinity stress-tolerant, were predominant in the granules and there was no significant difference in the microbial community of the granules by the salinity stress treatment. Our results suggest that the alleviation effect of the divalent cations on the salinity stress on the anammox granules might be associated with the increased production of different EPS rather than in changes to the anammox bacteria.

Effective Removal of Calcium and Magnesium Ions from Water by a Novel Alginate–Citrate Composite Aerogel

In this work, a novel alginate/citrate composite aerogel (CA–SC) was synthesized by chemical grafting technology combined with vacuum freeze-drying method, and CA–SC was used for removing calcium (Ca2+) and magnesium (Mg2+) ions from water. The experimental results indicate that the as-prepared CA–SC has a high affinity for Ca2+ and Mg2+ and can remove 96.5% of Ca2+ (or 96.8% of Mg2+) from the corresponding solution. The maximum adsorption capacities of CA–SC for Ca2+ and Mg2+ are 62.38 and 36.23 mg/g, respectively. These values are higher than those of the most reported Ca2+-sorbents and Mg2+-sorbents. The CA–SC adsorbent can be regenerated through a simple pickling step, and its adsorption performance keeps stable after repeated use. Analysis of the adsorption mechanism shows that the CA–SC combines Ca2+ and Mg2+ in water mainly through coordination effect.

Selective Adsorption of Amino Acids in Crystals of Monohydrocalcite Induced by the Facultative Anaerobic Enterobacter ludwigii SYB1

The morphology, crystal structure, and elemental composition of biominerals are commonly different from chemically synthesized minerals, but the reasons for these are not fully understood. A facultative anaerobic bacterium, Enterobacter ludwigii SYB1, is used in experiments to document the hydrochemistry, mineral crystallization, and cell surface characteristics of biomineralization. It was found that carbonate anhydrase and ammonia production were major factors influencing the alkalinity and saturation of the closed biosystem. X-ray diffraction (XRD) spectra showed that calcite, monohydrocalcite (MHC), and dypingite formed in samples with bacterial cells. It was also found that the (222) plane of MHC was the preferred orientation compared to standard data. Scanning transmission electron microscopy (STEM) analysis of cell slices provides direct evidence of concentrated calcium and magnesium ions on the surface of extracellular polymeric substances (EPS). In addition, high-resolution transmission electron microscopy (HRTEM) showed that crystallized nanoparticles were formed within the EPS. Thus, the mechanism of the biomineralization induced by E. ludwigii SYB1 can be divided into three stages: (i) the production of carbonate anhydrase and ammonia increases the alkalinity and saturation state of the milieu, (ii) free calcium and magnesium ions are adsorbed and chelated onto EPS, and (iii) nanominerals crystallize and grow within the EPS. Seventeen kinds of amino acids were identified within both biotic MHC and the EPS of SYB1, while the percentages of glutamic and aspartic acid in MHC increased significantly (p < 0.05). Furthermore, the adsorption energy was calculated for various amino acids on seven diffracted crystal faces, with preferential adsorption demonstrated on (111) and (222) faces. At the same time, the lowest adsorption energy was always that of glutamic and aspartic acid for the same crystal plane. These results suggest that aspartic and glutamic acid always mix preferentially in the crystal lattice of MHC and that differential adsorption of amino acids on crystal planes can lead to their preferred orientation. Moreover, the mixing of amino acids in the mineral structure may also have a certain influence on the mineral lattice dislocations, thus enhancing the thermodynamic characteristics.

Comparing the Effects of Calcium and Magnesium Ions on Accumulation and Translocation of Cadmium in Rice

Rice is one of China's most important food crops, and it is considered the primary source of human exposure to cadmium (Cd) pollution. A hydroponic experiment was performed to investigate the effect of calcium (Ca) and magnesium (Mg) on the absorption, distribution, and translocation of Cd in rice. Under the concentration gradient of Ca, Mg, and Cd, the concentrations of Cd in rice tissues were determined. The results revealed that the existence of Ca and Mg in the environment could benefit rice growth and limit the accumulation and translocation of Cd in plants. Cd concentrations in rice plants were as orders: roots > stems > leaves ≈ panicles ≈ husks > grains. While Cd content in rice grains decreased significantly under high Ca and Mg concentrations, this pattern was not observed under low and medium concentrations. Ca2+ and Mg2+ ions significantly influenced the translocation of Cd in the environment-rice system. Under the Ca (Mg)-deficient and Ca (Mg)-rich conditions, the husk and panicle played an essential role in hindering Cd transport to the rice grain, respectively. At the same concentration, the effect of Ca on the decrease of Cd bioconcentration was greater than that of Mg. An apparent antagonism was observed between Cd and Ca (Mg) in different parts of the rice plant. Altogether, the results of this study indicate that it was possible to plant and grow rice in Cd-polluted soil and that the accumulation and translocation of Cd in rice plants could be reduced by optimizing soil nutrient elements.

Comparison of acid degumming methods and their influence on the formation of 3-MCPD-esters and glycidyl esters in sunflower oil deodorization

Degumming is the first stage in processing of vegetable oils, and it is aimed at removing phospholipids. The article compares the results of degumming by phosphoric and citric acids, their effects on the extraction of calcium and magnesium ions from oils, these ions being the main components of nonhydratable phospholipids. We showed the appropriateness of combining citric and succinic acids (the final content of phospholipids in oil was 0.034%, whereas it was equal to 0.048% when citric acid was used) and citric and ascorbic acids (the final content of phospholipids in oil was 0.040%). We studied the effect of acid degumming on the formation of 3-MCPD-esters and glycidyl esters. The content of glycidyl esters after degumming with citric acid and phosphoric acid was 310 g kg–1 and 200 g kg–1, respectively. After degumming with citric acid and phosphoric acid, the content of 3-MCPD-esters in the deodorized oil was 680 g kg–1 and 470 g kg–1, respectively. On the contrary, aqueous degumming does not increase the content of these esters in the deodorized sunflower oil (the content is less than 100 g kg–1) and its implementation can be recommended as one of the ways to prevent the formation of these toxic substances during deodorization.

Performance of Resins Based on Poly(Divinylbenzene-co-Methyl Methacrylate)-Based Resins for Removal of Removing Calcium and Magnesium Ions from Water

Background: The mixing of the formation water present in oil and gas reservoirs and the injection water (often seawater) can form inorganic incrustations, during enhanced oil recovery operations. In this case, the cations (calcium, barium, strontium, iron, magnesium, etc.) of the injection water react with the anions (mainly sulfate and carbonate) of the formation water, produce Such inorganic salts can that precipitate in the reservoir rock, damaging the oil production. pipes and production lines, clogging them. One of the ways to prevent this problem is to remove the cations from the injection water, but this is a challenging procedure. Objective: In this study, the Sulfonated polymerdivinylbenzene (DVBS) and the copolymer sulfonated poly(methyl methacrylate-co-divinylbenzene (MMA-DVB) were compared in their efficiencies in reducing to a very low levels the concentration of removing chemically modified with sulfonic (S) groups to ascertain their performance in removing the calcium and magnesium ions present in water. Method: The resins were modified with sulfonic groups and characterized. We used central composition planning with batch tests to evaluate the adsorption, which occurred significantly for both ions using both resins with contact time of 10 minutes. Results: For both resins, calcium was preferentially adsorbed in relation to magnesium. Conclusion: Taking is account cost benefit, the copolymer MMA-DVBS (a less expensive adsorbent than the polymer DVBS) presented a satisfactory behavior, making it a potential material for treatment of water.