Effect of various steps of purification on ash content and ash constitution of cellulose. II. Cellulose prepared from sugar-cane bagasse

The effect of the various steps of purification on the ash content and ash constitution of cellulose prepared from bagasse has been examined. After each step of purification, samples were analysed for total ash, SiO₂, Ca, Fe and Mn. Two schemes of purification have been investigated. The first involves acid prehydrolysis, alkaline pulping and bleaching, and the second water prehydrolysis, acid pulping and bleaching. The first scheme has a better effect in diminishing the ash content, and gives a pulp containing 95.8% alpha cellulose with a 90% degree of whiteness.     

Studies in chemically modified celluloses. XI. Hypochlorite oxidation of cellulose in the presence of chromium oxide

In the dyeing of mineral Khaki on cotton fabrics, which are mainly used for military uniforms in India, a mixture of Fe₂O₃ and Cr₂O₃ is deposited in the fabric. When these garments are laundered using bleaching powder solution, the chromium oxide is likely to accelerate the oxidation of cotton cellulose. This aspect has been studied by oxidizing cotton yarn with sodium hypochlorite solution in the presence of chromium oxide, varying the chromium content, the pH of the oxidizing medium, and the concentration of the oxidizing agent. The properties of these chemically modified celluloses indicate that chromium oxide does accelerate the hypochlorite oxidation of cellulose and that the maximum extent of acceleration takes place when the oxidation is carried out at pH 7. The oxidized products were further modified separately by treatment with chlorous acid and sodium borohydride, and the effects of these agents on the properties of the oxidized products were studied.     

Studies in chemically modified celluloses. VIII. Hypochlorite oxidation of cellulose in the presence of cuprous hydroxide

Cotton cellulose has been oxidized with aqueous sodium hypochlorite solution in the presence of cuprous hydroxide for a short time (10 min). The copper hydroxide content, the pH of the oxidizing medium, and the concentration of the oxidant were varied and their effect on the chemical and physical properties of cellulose has been studied. Cuprous hydroxide has been shown to possess intense catalytic activity in this oxidation. The oxidized products are further modified by chlorous acid and sodium borohydride treatments and their effects on the properties of the oxidized products studied.     

Processing and kinetics studies on the alumina enrichment of coal fly ash by fractionating silicon dioxide as nano particles

Coal fly ash produced in the northern China is a potential bauxite substitute for aluminum production because of its high alumina content. However, this industrial application has been limited for its high silicon content. Alumina enrichment by removing silicon becomes a key technology for its utilization. A novel process was developed to fractionate the coal fly ash into high purity nano silicon particles and aluminum enriched residual ash. The procedure has major steps as sodium silicate dissolution with sodium hydroxide, first carbonation to remove impurities, second carbonation to precipitate silicon, and silicon precipitate recovery as a mesospheric nano particles product. Morphological and X-ray diffraction evidences indicated the glassy amorphous silicon content of the ash was dissolved in the sodium hydroxide solution whereas mullite remained in the residue. Kinetics study indicated that the second carbonation was a kinetically second order medium fast multi-phase reaction in which sodium silicate was precipitated as silicic acid. It was found that the reaction was controlled by the mass transferring resistance in the liquid membrane. These nano silicon dioxide particles were in size of 50 nm with a purity of 96%. Alumina content in process residue was slightly increased from 42.00 to 49.20%. Silicon dioxide content was reduced from 48.89 to 30.26%. Ratio of alumina/silica was increased from 0.86 to 1.63.     

Studies in Accelerated Oxidation of Cellulose. I—Hypochlorite Oxidation of Cellulose in Presence of Manganous Hydroxide

The oxidation of cellulose by treatment with sodium hypochlorite in the presence of different amounts of manganous hydroxide at different pH values (4·5–9·0) for a short time (10 min) has been investigated. Treatments with chlorous acid and sodium borohydride have been utilised to determine the different types of reducing and acidic groups formed in cellulose during accelerated oxidation. Manganous hydroxide has been shown to be a milder accelerant of the hypochlorite oxidation of cellulose than either leuco vat dyes or ferrous hydroxide under similar conditions.     

Fabrication and characterization of hardened bodies from Japanese volcanic ash using geopolymerization

Hardened bodies were fabricated from Japanese volcanic ash after mixing with an alkali solution, molding, and curing. The volcanic ash was composed of approximately 70% crystalline anorthite sodium [(Ca, Na) (Si, Al)₄O₈] phase and ≤30% amorphous silicate phase. First, a starting mixture was prepared by mixing the ground volcanic ash with a sodium hydroxide solution. The mixture was placed in a plastic mold using a glass rod, and then cured at 50 °C and 80% relative humidity for 3 days. The compressive strength of the resulting hardened body increased with increasing concentration of sodium hydroxide solution. When a 13.5 mol/L sodium hydroxide solution was used, the average compressive strength of the hardened body reached 80.1 MPa. The hardening mechanism for the volcanic ash during curing is discussed.     

Zeolite synthesis from paper sludge ash with addition of diatomite

BACKGROUND: This study aimed to investigate the synthesis of zeolites from paper sludge ash (PSA) with added diatomite to remove both NH₄⁺ and PO₄^3? for water purification. The PSA had low Si and significant Ca contents. Four types of diatomite: white (T‐W) and brown (T‐B) from deposits of marine origin in Takanosu, and white (S‐W) and gray (S‐G) from lacustrine deposits in Shonai, were added to NaOH solution to increase the Si content and thereby synthesize zeolites with high cation exchange capacity (CEC). RESULTS: The order of the amounts of Si extracted from the diatomite to the alkali solution was S‐W > T‐W = T‐B > S‐G, which correlates with the amorphous SiO₂ content of diatomite. The original ash without addition of diatomite yielded hydroxysodalite with CEC of about 1.0 mmol g^?1. For all samples, the addition of diatomite to the solution yielded zeolite‐P with a higher CEC, but the addition of excess Si inhibited the synthesis of zeolite‐P, and the CEC of the product was low. A product with high CEC including zeolite‐P was obtained in a solution with around 500 mmol L^?1 of Si concentration, and had the ability to remove both NH₄⁺ and PO₄^3?. CONCLUSION: Diatomite has the potential for used as an additive for the synthesis of high CEC zeolite from PSA. The product with zeolite‐P exhibited relatively high CEC, capacity for NH₄⁺ uptake, and the ability to remove PO₄^3? by precipitation, which is preferable for water purification applications. Copyright © 2008 Society of Chemical Industry     

Effect of nano-silica on the chemical durability and mechanical performance of fly ash based geopolymer concrete

In this study, the effect of nano silica on the short term severe durability performance of fly ash based geopolymer concrete (GPC) specimens was investigated. Four types of GPC were produced with two types of low calcium fly ashes (FAI and FAII) with and without nano silica, and ordinary Portland cement concrete (OPC) concrete was also cast for reference. For the geopolymerization process, the alkaline activator has selected a mixture of sodium silicate solution (Na₂SiO₃) and sodium hydroxide solution (NaOH) with a ratio (Na₂SiO₃/ NaOH) of 2.5. Main objectives of the study were to investigate the effect of usability or replaceability of nano silica-based low calcium fly ash based geopolymer concretes instead of OPC concrete in structural applications and make a contribution to standardization process of the fly ash based geopolymer concrete. To achieve the goals, four types of geopolymer and OPC concretes were subjected to sulfuric acid (H₂SO₄), magnesium sulfate (MgSO₄) and seawater (NaCl) solutions with concentrations of 5%, 5%, and 3.5%, respectively. Visual appearances and weight changes of the concretes under chemical environments were utilized for durability aspects. Compressive, splitting tensile and flexural strength tests were also performed on specimens to evaluate the mechanical performance under chemical environments. Results indicated that FAGPC concretes showed superior performance than OPC concrete under chemical attacks due to low calcium content. Amongst the chemical environments, sulfuric acid (H₂SO₄) was found to be the most dangerous environment for all concrete types. In addition, nano silica (NS) addition to FAGPC specimens improved both durability and residual mechanical strength due to the lower porosity and more dense structure. The FAIIGPC specimens including nano silica showed the superior mechanical performance under chemical environment.     

Uranium recovery from coal ash dumps of Mongolia

The concentration of natural radionuclides and the feasibility of recovery of uranium from browncoal ash of a Mongolian cogeneration plant were investigated. The concentrations of the elements were determined by instrumental gamma-activation (IGAA) and X-ray fluorescence (XRF) analysis. Uranium from brown-coal ash was leached with an 8 M HNO₃ + HF (10%) mixture. The extraction of uranium from the solution and its purification for the removal of accompanying elements were carried out on an anion exchanger. An ash sample after leaching contains neither natural radioactive elements (²³⁸U and ²³²Th) nor their decay products, thereby allowing for the use of the ash as a building material.     

缓冲溶液对TEMPO/NaClO/NaBr选择性氧化纤维素的影响

TEMPO/NaClO/NaBr氧化体系被广泛应用于选择性氧化糖类C6位伯醇羟基,使其成为羧酸盐物质,从而获得更好的水溶性或其他特定功能。但在氧化反应过程中,pH随反应的进行下降,并且存在pH值持续控制繁琐等问题。实验比较分析TEMPO/NaClO/NaBr氧化纤维素在碳酸钠―碳酸氢钠缓冲溶液、硼砂―氢氧化钠缓冲溶液中的适用性,并以滴加的方式向体系中加入氧化剂NaClO溶液,探索两种缓冲体系中各自适宜的NaClO滴加速度。实验结果表明,碳酸钠―碳酸氢钠缓冲溶液和硼砂―氢氧化钠缓冲溶液都适用于TEMPO/NaClO/NaBr氧化体系。与传统方法相比,氧化纤维素的羧基含量可以提高20%～25%。使用缓冲溶液较单一氢氧化钠溶液对稳定pH值有更好的效果,并且方法简便。另外,硼砂―氢氧化钠缓冲溶液对NaClO滴加速度敏感,控制滴加速度可以有效地提高反应活性。     

废次氯酸钠中乙炔的闪蒸回收及废液回用复配次氯酸钠

介绍了废次氯酸钠中乙炔气的闪蒸回收及废液回用复配次氯酸钠的工艺、实际生产情况,废液的回用可节约大量水资源,实现污水零排放。     

Reducing fly ash deposition by pretreatment of brown coal: Effect of aluminium on ash character

The effect of pretreatment on the structure and the related fouling/slagging behaviour of fly ash from brown coal has been investigated. Condensable sodium salts and low melting sodium silicates are known as fouling and slagging materials. Experimental proof is given that less of such components were formed after treatment of Loy Yang brown coal with water and, particularly, with Al compounds.For the range of temperatures applied (1000–1400°C) in a drop tube furnace, the quantity of condensable salts generated was found to depend only on the amount of sodium in Loy Yang coal. Aluminium had the effect of reducing the sodium level by ion exchange and thus the formation of fouling ash components. The stickiness of sodium silicates from this coal was also shown to be reduced by aluminium.     

次氯酸钠溶液对荧光增白剂的氧化

研究了次氯酸钠溶液对荧光增白剂CBS-X和31#的氧化作用、CBS-X和31#水溶液经紫外光老化过程,考察了荧光增白剂含量不同的洗衣液对黄变织物的增白作用。结果表明,CBS-X和31#都不能在次氯酸钠溶液和紫外光照下长期稳定存在,CBS-X与次氯酸溶液接触3.5 h或经紫外光照射96 h后在348 nm处不再具有吸收;31#与次氯酸钠溶液接触10 min或经紫外光照射96 h后345.5 nm处吸收峰消失,267 nm处生成新吸收峰。经荧光增白剂处理的织物经高质量分数次氯酸钠溶液洗涤易黄变,含质量分数0.2?S-X的洗衣液对被次氯酸钠溶液漂黄的织物增白效果较佳。     

电镀废水处理技术与实践

用次氯酸钠溶液和双氧水组合的方法处理含氰废水,效果好且成本低。可以用双氧水处理含镍废水中的氰化物,但不能使用次氯酸钠溶液,在碱性条件下Ni 2+被次氯酸钠氧化生成Ni(OH)3沉淀。设置两个中和池,在一级中和池中加入石灰处理掉约90%的废酸,同时在二级中和池中加入石灰处理剩余的废酸。在二级中和池中用pH自动控制系统控制石灰的加入量,保证排放水的浊度达到标准。     

Destruction of aflatoxins in peanut protein isolates by sodium hypochlorite

Sodium hypochlorite has been tested for destruction of aflatoxins during the preparation of peanut protein isolates from raw peanuts and defatted peanut meal. The treatments were evaluated by determination of the aflatoxins in the products by thin layer chromatography. Effects of sodium hypochlorite concentration, reaction pH, temperature, and time were studied. Results show that both the sodium hypochlorite concentration and pH are important factors in reducing the concentration of aflatoxins in the protein isolates to nondetectable levels. The treatment with 0.4% sodium hypochlorite at pH 8 produced protein isolates with trace amounts of aflatoxins B₁ and B₂ from ground raw peanuts containing 725 ppb aflatoxin B₁ and 148 ppb aflatoxin B₂, whereas untreated protein isolates contained 384 ppb aflatoxin B₁ and 76 ppb aflatoxin B₂. At pH 9, 0.3% sodium hypochlorite reduced the aflatoxin B₁ content in the protein isolates from 300 ppb to below detectable quantities and the aflatoxin B₂ content from 52 ppb to 2 ppb. Similar results were obtained at pH 10 for 0.3% sodium hypochlorite concentration. In the case of defatted peanut meal which contained 136 ppb aflatoxin B₁ and 36 ppb aflatoxin B₂, 0.25% sodium hypochlorite concentration at pH 8 (0.20% at pH 9; 0.15% at pH 10) reduced both the aflatoxin B₁ and B₂ contents to below detectable quantities in protein isolates as compared to aflatoxin levels of ca. 75 ppb B₁ and 17 ppb B₂ in the untreated protein isolates. Reaction temperature and time did not affect the destruction of aflatoxins significantly.     

煅烧活化粉煤灰对镓酸浸效果的实验研究

通过高温煅烧法对粉煤灰进行活化,采用酸浸法浸取活化后粉煤灰中的镓。研究了煅烧条件（助剂种类、助剂含量、煅烧温度、煅烧时间）对粉煤灰中镓的浸出效果的影响。采用X射线衍射表征粉煤灰以及不同煅烧条件下所得产物的物相组成,用ICP测定了浸取液中的镓的含量。研究结果表明：在3种助剂（碳酸钠、碳酸钙和氧化钙）中,碳酸钠是粉煤灰活化的最优助剂;碳酸钠与粉煤灰的质量比为1.5∶1、煅烧温度为800 ℃、煅烧时间为120 min时,粉煤灰中镓的浸出量（质量分数）为5.262×10-5。     

Thin fly ash/ ladle furnace slag geopolymer: Effect of elevated temperature exposure on flexural properties and morphological characteristics

The flexural properties and thermal performance of 10 mm-thin geopolymers made from fly ash and ladle furnace slag were evaluated before and after exposure to elevated temperatures (300 °C, 600 °C, 900 °C, 1100 °C and 1150 °C). Class F fly ash was mixed with liquid sodium silicate (Na₂SiO₃) and 12 M sodium hydroxide (NaOH) solution using aluminosilicate/activator ratio of 1:2.5 and Na₂SiO₃/NaOH ratio of 1:4 to synthesise thin fly ash (FA) geopolymers. 40 wt% of ladle furnace slag was partially replacing fly ash to produce fly ash/slag-based (FAS) geopolymers. Thermal treatment enhanced the flexural strength of thin geopolymers. In comparison to the unexposed specimen, the flexural strength of FA geopolymers at 1150 °C and FAS geopolymers 1100 °C was increased by 161.3% to 16.2 MPa and 208.9% to 24.1 MPa, respectively. A more uniform heating was achieved in thin geopolymers which favoured the phase transformation at high temperatures and contributed to the substantial increase in flexural strength. The joint effect of elevated temperature exposure and the incorporation of ladle furnace slag further improved the flexural strength of thin geopolymers. The calcium-rich slag refined the pore structure and increased the crystallinity of thin geopolymers which aided in high strength development.     

Leaching behavior of heat-treated waste ash

The leaching behavior of heat-treated waste ash was studied to verify the possibility of the thermal treatment of waste incineration ash in existing incinerators and boiler combustion chambers. The influence of temperature, oxygen concentration and treatment time on the leaching behaviors of harmful heavy metals, especially lead (Pb) and chromium(VI) (Cr (VI)) were studied to clarify effective treatment conditions to suppress leaching. By examining the leaching behavior of Pb and Cr from ash heat-treated under various conditions, it was found that leaching can be suppressed by heat-treating the ash under conventional combustion conditions of around 900-1000 °C at 5-10% oxygen concentration. The leaching behaviors of Pb and Cr (VI) from real ash with different particle sizes and from model samples were also investigated in detail to find an effective method to suppress Pb leaching. It was found that the formation and growth of gehlenite (SiO₂·2CaO·Al₂O₃) in the ashes led to the decrease in the amount of Pb leaching. Therefore it was considered that the addition of an inorganic matrix with a high silica content that can promote gehlenite growth in the ash, for example, coal ash or waste glass is effective to suppress of Pb leaching.     

CTA中灰分降低的操作优化

分析了CTA中灰分的组成,讨论了过滤机效果、催化剂用量、系统Na+含量、母液循环率、系统腐蚀以及负荷变化对灰分的影响,提出降低PTA中灰分含量的措施。     

提高次氯酸钠溶液稳定性

通过次氯酸钠溶液有效氯含量的测定，对次氯酸钠溶液的稳定性进行了初步分析探讨，提出了一些应对措施。