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2 Conversion
Published in Yun Zheng, Bo Yu, Jianchen Wang, Jiujun Zhang, Carbon Dioxide Reduction through Advanced Conversion and Utilization Technologies, 2019
Yun Zheng, Bo Yu, Jianchen Wang, Jiujun Zhang
The indirect (multistep) process consists of the pretreatments and subsequent aqueous carbonation process. The chemical, thermal, and mechanical pretreatments are introduced to improve aqueous rock dissolution and activate the particles, including extracting magnesium and calcium from minerals. Weak acids (such as citrates and oxalates), HCl and NaOH solutions are mostly used in the intermediate process.33,34 For example, Kakizawa et al.46 and Yuen et al.40 have reported a process including two steps, with the dissolution of silicate by acetic acid and the carbonation of calcium acetate, as shown in Figure 3.6. The final products in the indirect approach is usually purer compared to the direct approach. There are still many challenges to using the indirect conversion routes, including the huge energy input and the unrecovered intermediate chemicals. More research to optimize the technical route is needed.
Bleaching of Cellulosic and Synthetic Fabrics
Published in Menachem Lewin, Stephen B. Sello, Handbook of Fiber Science and Technology: Volume I Chemical Processing of Fibers and Fabrics, 2018
The characterization of the oxidized celluloses has been widely investigated and comprises determinations of the aldehyde, ketone, and carboxyl groups as well as the degree of polymerization [31, 32, 42, 44, 58–66]. The determination of the functional groups requires considerable caution [60], since usually their concentrations are low. In addition the values obtained frequently depend on the accessibility of the cellulose and its state of swelling, which limits the penetration of the reagents and their access to the groups to be determined. Furthermore, the impurities invariably present in the cellulose frequently interfere with several analytical determinations, especially those of the carboxyl groups, which may be rendered inaccurate due to the presence of residual metallic bases in the fibers [58, 60]. This is particularly true for methods based on acidimetric titrations of samples treated with salt solutions, followed by estimation of the liberated anions. (For example, the cellulose is soaked in a solution of sodium chloride or calcium acetate, and the liberated hydrochloric or acetic acid is estimated.) All these methods require a pretreatment with dilute mineral acid which subsequently has to be thoroughly removed [58]. The only method for carboxyl determination which does not require such a prewash is the method based on the direct estimation of the methylene blue cations absorbed on the carboxyl groups of the cellulose, from a solution of the hydrochloride buffered at pH 8.4 with veronal [34, 63].
Biological Production of Ethanol from Coal Synthesis Gas
Published in Donald L. Wise, Bioprocessing and Biotreatment of Coal, 2017
S. Barik, S. Prieto, S. B. Harrison, E. C. Clausen, J. L. Gaddy
Many strains of yeast (mostly Candida sp.) have been found to convert acetate to citric acid [44,45,47,54]. Acetic acid or calcium acetate was used as the substrate for citric acid fermentation by the yeast.
A systematic review on MICP technique for developing sustainability in concrete
Published in European Journal of Environmental and Civil Engineering, 2023
Santosh Ashok Kadapure, Umesh B. Deshannavar, Basavaraj G. Katageri, Poonam S. Kadapure
Another important requirement for MICP process is calcium source. The optimum concentration of urea and calcium chloride was reported to be 0.5 and 0.25 M in much research works (De Muynck et al., 2008). Calcium chloride is a common calcium source form MICP process. The common source of calcium reported in most of the studies is calcium chloride in microbial technique. But chloride in concrete can cause electrochemical corrosion of steel bars, which lowers the efficiency of durability property. To overcome this drawback, some researchers have used other sources of calcium, such as calcium acetate and calcium nitrate. Achal (2015) used five different types of calcium sources in their work (calcium chloride, calcium nitrate, calcium oxide, calcium acetate and calcium acetate). The maximum efficiency for CaCO3 precipitation was greater for calcium chloride, and minimum for calcium oxide. Van Tittelboom et al. (2010) applied calcium chloride, calcium acetate and calcium nitrate at the surface of cracked specimens. The performance by using three chemical treatment was found to have same effectiveness in improving durability property.
Soluplus-stabilized 5-fluorouracil-entrapped niosomal formulations prepared via active and passive loading techniques: comparative physico-chemical evaluation
Published in Journal of Dispersion Science and Technology, 2023
Onyinyechi Lydia Ugorji, Olisa Ivy Okoye, Chinekwu Nwangwu, Chinazom Precious Agbo, Franklin Chimaobi Kenechukwu
Drugs can be passively loaded into niosomes by ether/ethanol injection, reverse phase evaporation, and thin film hydration methods. The active loading approach involves precipitating the medication (in the aqueous core of the vesicles) in the presence of an acetate ion transmembrane gradient.[6,7] The active loading approach reportedly has higher encapsulation efficiency than the thin film hydration method (passive loading).[4,6] The application of the active loading approach to load pharmaceuticals into niosomal vesicles is only now being investigated, despite the fact that it has been extremely effective at trapping hydrophilic medications in liposomal vesicles. Using calcium acetate, Varshosaz et al.[7] generated vitamin C-loaded niosomes and reported an EE of 85.94%, whereas Dehaghi et al.[6] produced ocular dorzalamide HCl-loaded niosomes using a di-ammonium hydrogen phosphate gradient and recorded an EE of 47.70%.
Optimizing protocols for microbial induced calcite precipitation (MICP) for soil improvement–a review
Published in European Journal of Environmental and Civil Engineering, 2022
Tong Yu, Hanène Souli, Yoan Péchaud, Jean-Marie Fleureau
For injecting cementation solution, commercial chemical reagents (urea and Ca2+ ions) are used. For sustainable, environmental and cost-effective consideration, researchers used alternatives to replace pure chemical reagents in specific regions. According to Danjo and Kawasaki (2016), urea available in coastal regions, resulting for instance from biodegradation of dead fish as well as urine from animals, can be used as carbon source. In a limited-resource-region like Sahel in Sahara desert (Bernardi, 2012), urea from urine and calcium possibly from bones and milk are used to produce bricks together with sand and soil bacteria as building material. Using urine is under debate because of the related sanitary problems (water pollution, health risk). Chemical reagents (like calcium chloride, calcium acetate) are used as calcium source. Cheng et al. (2014) successfully used seawater as calcium source. Liang et al. (2019) proposed to use kitchen waste (oyster shells, scallop shells and eggshells) instead of pure reagents. Though these usages of waste are promising, attention should be paid to the problems like sanitary problems or secondary pollution.