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1.
Anhydrites(II)- CaSO4 were prepared from two waste gypsums (PRECHEZA Perov, FOSFA Potorná). The samples of anhydrites(II) with sulphate activators were tested on spillage, beginning and the end of setting time, bending and pressure strength. Both sodium and potassium sulphates accelerated setting of anhydrite, more impressively that prepared from Potorná gypsum. The addition of Na2SO4 influenced the strength of this anhydrite very favourably. On the contrary K2SO4 influenced favourably the strength of Perov anhydrite. Results confirm the necessity to evaluate properties of such materials with respect to their origin. 相似文献
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Sustainable composites comprising scraps of high-density polyethylene (HDPE) and gypsum waste in proportions HDPE/gypsum 100/0, 50/50, 40/60, and 30/70 wt% were prepared. The morphology of the injected specimens was core-shell. Thermal, flammability, water absorption, and compression resistance were also evaluated. Progressively, the presence of gypsum increased the HDPE crystallinity and Tonset. Concerning the flammability, the composite 30/70 exhibited the burning rate three times lower than HDPE, indicating that the gypsum played a role as a flame retardant. The HDPE acted as waterproofing for gypsum. The compression resistance of the composites was similar to HDPE. 相似文献
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Desulfurized gypsum (DG) as a soil modifier imparts it with bulk solid sulfite. The Fe(III)–sulfite process in the liquid phase has shown great potential for the rapid removal of As(III), but the performance and mechanism of this process using DG as a sulfite source in aqueous solution remains unclear. In this work, employing solid CaSO3 as a source of SO32−, we have studied the effects of different conditions (e.g., pH, Fe dosage, sulfite dosage) on As(III) oxidation in the Fe(III)–CaSO3 system. The results show that 72.1% of As(III) was removed from solution by centrifugal treatment for 60 min at near-neutral pH. Quenching experiments have indicated that oxidation efficiencies of As(III) are due at 67.5% to HO•, 17.5% to SO5•− and 15% to SO4•−. This finding may have promising implications in developing a new cost-effective technology for the treatment of arsenic-containing water using DG. 相似文献
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Rising concerns over the use of fossil resources have generated renewed interest in the production of commodity chemicals
via fermentation. Organic acids are a particularly attractive target because their functionality enables downstream catalytic
upgrading to a variety of compounds. In this article, we survey how common technical issues are addressed in the recovery
schemes for several organic acids. We present results for the recovery of acetate using a new method based on amine complexation.
Our reactive separation scheme produces a high-purity product, is energy efficient, and avoids the coproduction of a waste
salt coproduct, all prerequisites for a large-scale production process. 相似文献
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Salt efflorescences consisting of gypsum sampled mainly in the Schirmacher Oasis have been analyzed for the isotopic composition of the water of crystallization and of the sulphate-sulphur. For comparison, a few samples from other Antarctic locations (Guettard Range, Prince Charles Mts., Insel Mts.) were included in the study. The isotopic variations of the water of crystallization of secondary gypsum and the calculated isotopic composition of the mother solution reflect the local climatic conditions during the precipitation of the efflorescences. It is therefore possible to obtain qualitative information about the climatic conditions prevailing in the studied region. 相似文献
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The spontaneous precipitation of calcium sulfate dihydrate (gypsum) at 30 °C was investigated in the presence of polyelectrolytes. The degree of inhibition is measured as the reduction in initial crystallization rate, determined by conductivity of the crystallizing solution. The inhibition increases with acid content of the copolymer. Changing the butyl ester to a hydrophilic ethylene oxide resulted in higher inhibition efficiency. The inhibition efficiency is believed to arise from the closer chain packing on the crystal surface. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Failure of rock mass that is subjected to compres-sive loads occurs from initiation, propagation, and linkage of new cracks from preexisting fissures. Our research inves-tigates the cracking behaviour and coalescence process in a brittle material with two non-parallel overlapping flaws using a high-speed camera. The coalescence tensile crack and tensile wing cracks were the first cracks to occur from the pre-existing flaws. The initiation stresses of the primary cracks at the two tips of each flaw were simultaneous and decreased with reduced flaw inclination angle. The following types of coalescence cracks were identified between the flaws: pri-mary tensile coalescence crack, tensile crack linkage, shear crack linkage, mixed tensile-shear crack, and indirect crack coalescence. Coalescence through tensile linkage occurred mostly at pre-peak stress. In contrast, coalescence through shear or mixed tensile-shear cracks occurred at higher stress. Overall, this study indicates that the geometry of preexisting flaws affect crack initiation and coalescence behaviour. 相似文献
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D. Montagnino E. Costa F. R. Massaro G. Artioli D. Aquilano 《Crystal Research and Technology》2011,46(10):1010-1018
Gypsum is the most abundant natural sulphate, and in industrial application it plays an important role in gypsum based binders. Furthermore, it plays a critical role in the hydration of Portland cement, and then gypsum is one of the most important cement additive. In this paper we investigated the role of two commercial polymeric additives in modifying the crystal habits and size of gypsum, growth in aqueous solution. These two additives belong to the categories of acrylic polymers and they are known only by their commercial names of SP1 and SP3. We found that these substances can act as shape modifiers mainly at concentration over 0.04% by weight, with a shortening in the elongation of gypsum crystal and some change in the characters of {001} form, from stepped to flat, due to a change in the growth mechanism. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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为查明以工业石膏为原料制备石膏晶须时溶解的杂质离子对晶须的影响,在分析典型工业石膏主要杂质离子的基础上,对溶液中含有Na+、Al3+、K+、Sr2+、Mg2+和F-杂质离子时石膏晶须的制备进行了研究.采用XRD、IR 光谱、光学显微镜和ICP-AES对石膏晶须样品进行了表征,讨论了杂质离子对石膏晶须物相、结构、化学组成和形貌的影响.结果表明,碱金属离子Na+、K+及高电荷惰性气体型离子Al3+对石膏晶须的形貌无明显影响;碱土金属离子SF2+、Mg2+能够提高晶须的长度和长径比;阴离子F-不仅会引起晶须呈帚状聚集,而且会导致晶须的纯度降低.杂质离子在石膏晶须生长过程中可不同程度地进入晶格代替Ca2+或SO42-.工业上制备石膏晶须时可采用Sr2和Mg2提高晶须的长度和长径比,应避免高浓度的Na+、K+和Al3+以及F-对晶须造成的不利影响. 相似文献