Effects of Mg-based Alkaline Peroxide Bleaching on Physical Properties of Poplar Bleached Chemi-thermomechanical Pulp and Its Influence Mechanism

In this study,Mg O was partially used as an alkali source in the peroxide bleaching process of bleached chemi-thermomechanical pulp(BCTMP).The effects of substitution percentage of Mg O for Na OH on the bulk,optical,and physical properties of bleached pulp,and the main effluent characteristics were analyzed.In addition,the influencing mechanism of Mgbased alkali on the strength properties of the BCTMP was further investigated.Strength properties of the BCTMPs were investigated as a function of charge characteristics,fiber morphology,surface lignin content,relative bonding area,and hydrogen bonds of the BCTMP.The results showed that cationic demand(CD) and chemical oxygen demand(COD_(Cr)) of the bleaching effluent decreased as the substitution percentage of Mg O for Na OH increased; meanwhile,the bulk and optical properties of the BCTMP increased.Nevertheless,the strength properties(tensile,tear,and burst indices) of the bleached pulp decreased as the substitution percentage of Mg O for Na OH increased.The decrease in the fiber charge density and increase in the surface lignin content affected the fiber swelling,resulting in a decline in pulp interfibers bonding strength and further loss of the tensile and burst indices.

THE EFFECT OF TRANSITION METAL IONS-IRON ON HYDROGEN PEROXIDE BLEACHING

Hydrogen peroxide bleaching has been extensivelyused in high-yield pulp bleaching. Unfortunately,hydrogen peroxide can be decomposed underalkaline condition, especially when transition metalions exit. Experiments show that the valence oftransition metal ion is also responsible for thedecomposition of hydrogen peroxide.Iron ions are present in two oxidation states, Fe2+ andFe3+. They are both catalytically active to hydrogenperoxide decomposition. Because Fe3+ is brown, itcan affect the brightness of pulp directly, it can alsocombine with phenol, forming complexes which notonly are stable structures and are difficult to beremoved from pulp, but also significantly affect thebrightness of pulp because of their color.Sodium silicate and magnesium sulfate, when usedtogether, can greatly decrease hydrogen peroxidedecomposition. The optimum dosage of sodiumsilicate is about 0.1% (on solution) for Fe2~ and0.25% (on solution) for Fe3~. Adding chelants such asDTPA or EDTA with stabilizers simultaneously canobviously improve pulp brightness. For iron ions, thechelate effect of DTPA is better than that of EDTA.Under acidic conditions, sodium hyposulfite andcellulose can reduce Fe3+ to Fez+ effectively, and pulpbrightness is improved greatly. Adding sodiumthiosulfate simultaneously with magnesium sulfate,sodium silicate, and DTPA to alkaline peroxidesolution can result in higher brightness of pulp.pH is a key parameter during hydrogen peroxidebleaching, the optimum pH value should be 10.5-12.

THE EFFECT OF TRANSITION METAL IONS-MANGANESE ON HYDROGEN PEROXIDE BLEACHING

In this investigation, the catalytic activities of Mn(II),Mn(III) and Mn(IV) towards decomposing hydrogenperoxide were compared. Among Mn (II), Mn (III)and Mn (IV), Mn (II) is not catalytically active indecomposing hydrogen peroxide. However, both Mn(113) and Mn (IV) are, and Mn (III) has a strongereffect than Mn(IV).In addition, we also studied the practical methods todecrease the Mn-induced decomposition of hydrogenperoxide. The results showed that sodium silicate andmagnesium sulfite in combination can effectivelydecrease the decomposition of hydrogen peroxide.The optimum dosage of sodium silicate was about0.5% (on solution). Adding chelants such as DTPAor EDTA simultaneously with stabilizers candecrease hydrogen peroxide decomposition. For Mn(IV), the EDTA is more effective than DTPA.Adding sodium thiosulfate simultaneously withmagnesium sulfate, sodium silicate and DTPA toalkaline peroxide solution can result in more residualhydrogen peroxide, and a higher pulp brightness.

Effects of 45S5 bioglass on surface properties of dental enamel subjected to 35% hydrogen peroxide

Tooth bleaching agents may weaken the tooth structure. Therefore, it is important to minimize any risks of tooth hard tissue damage caused by bleaching agents. The aim of this study was to evaluate the effects of applying 45S5 bioglass （BG） before, after, and during 35% hydrogen peroxide （HP） bleaching on whitening efficacy, physicochemical properties and microstructures of bovine enamel. Seventy-two bovine enamel blocks were prepared and randomly divided into six groups： distilled deionized water （DDW）, BG, HP, BG before HP, BG after HP and BG during HP. Colorimetric and microhardness tests were performed before and after the treatment procedure. Representative specimens from each group were selected for morphology investigation after the final tests. A significant color change was observed in group HP, BG before HP, BG after HP and BG during HP. The microhardness loss was in the following order： group HP〉 BG before HP, BG after HP〉 BG during HP〉DDW, BG. The most obvious morphological alteration of was observed on enamel surfaces in group HP, and a slight morphological alteration was also detected in group BG before HP and BG after HP. Our findings suggest that the combination use of BG and HP could not impede the tooth whitening efficacy. Using BG during HP brought better protective effect than pre/post-bleaching use of BG, as it could more effectively reduce the mineral loss as well as retain the surface integrity of enamel. BG may serve as a promising biomimetic adjunct for bleaching therapy to prevent/restore the enamel damage induced by bleaching agents.

TCF Bleaching of Populus tomentosa Kraft Pulps with H_2O_2 Pretreatment un-der Acid Condition

The process of peroxide bleaching of Populus tomentosa kraft pulp with H2O2 pretreatment under acid condition was studied. The variations of pulp characteristics such as brightness, Kappa number and viscosity during the peroxide bleaching process were discussed and the concept of the A/B value was presented for the first time. The results show that acid pretreatment with H2O2 is essential to improve pulp brightness and avoid viscosity loss. The conclusion is reached that the A/B value has great influence on pulp properties when the total amount of peroxide used in the bleaching process is 2%-5%. Pulp with a high viscosity and brightness can be obtained when A/B is about 0.15.

Using Trace Metals, Peroxide, Acid and Iodine Values to Characterize Oils Bleached Using Clays from Central and Eastern Uganda

Bleaching of edible oils is known to alter the composition of oils as it removes impurities and certain food nutrients. The characteristics of bleached oil are strongly related to type bleaching medium, temperature at which bleaching is done and other factors. In this study, we compare peroxide, free fatty acid, acid and iodine values, copper and iron content of bleached and crude oils to establish the characteristics of edible oils bleached using smectite and kaolinite-rich clays. Oil industries spend large sums of money purchasing bleaching earths yet no country lacks natural clays which can be developed to bleach oils. In Uganda alone more than US$ 700,000 is spent every month yet many clay deposits are unexploited. In this study, we have documented trace metal composition, peroxide values, acid values, iodine values and free fatty acid content of bleached and unbleached cotton-seed and sunflower seed oils. The bleached oils were found to be fit for human use. Clays are either kaolinites or smectites, but the clays used to bleach edible oils are montmorillonites or bentonites. The decrease in content of iron in the bleached oils was highest for all oils bleached. The content of copper showed the smallest change. The content of copper in cotton oils decreased from 0.5 ppm to 0.15 ppm using Kajansi clay leached in 20% acid yet when Chelel clay leached under similar conditions was used decrease was from 0.5 to 0.1 ppm. The content of iron in sunflower oils bleached using Kajansi clay leached in 20% acid decreased from 1.6 to 0.2 ppm yet that bleached with Chelel clay under similar conditions decreased to 0.1 ppm. The acid values showed that the acidity in sunflower oils is largely due to oleic acid as the average value for acids is in the range close to oleic acid, cotton-seed oil corresponded to linoleic acid. The levels of free fatty acid were found to lie in range from 3.8 - 3.2 for all clays used showing no significant rise. The peroxide values of bleached oils lay between 1.2 and 0.8.

STUDY ON THE ELEMENTAL CHLORINE FREE BLEACHING OF BAMBOO KRAFT PULP

The influential factors of DQP bleaching, chlorine dioxide bleaching, chelation and hydrogen peroxide bleaching, of bamboo kraft pulp were studied. The pH value in D stage, dosage of EDTA in Q stage and charge of MgSO4 in P stage were optimized. The results indicated that good results of chlorine dioxide bleaching were obtained under the conditions of ClO2 2.0%,pH 4, and the highest final brightness(86.4%ISO) and the lowest final Kappa number(1.37) were attained when the charge of EDTA in Q stage was 0.4%, charge of MgSO4 in P stage was 0.2%, and the other conditions of P stage : pulp consistency 10%, H2O2 charge 2.5%, NaOH charge 1.4%, temperature 90℃ and time 120 min. A comparison of bleaching results, pulp strength and effluent characteristics of bamboo kraft pulp between DQP and CEH sequences was done. The results indicated that bamboo kraft pulp could be bleached to brightness of above 83%ISO by both DQP and CEH sequences. Compared with CEH bleached pulp, DQP bleached pulp had slightly lower brightness, better brightness stability, higher pulp viscosity, better strength properties and lower pollution loads.

新型过氧化氢稳定剂的制备及性能研究

本研究以马来酸-丙烯酸共聚物(MA-AA)为主体稳定剂,与螯合型助剂复合,制备了新型过氧化氢(H_(2)O_(2))稳定剂,通过测定新型H_(2)O_(2)稳定剂对金属离子的螯合值、H_(2)O_(2)分解率及进行化机浆H_(2)O_(2)漂白实验,研究新型H_(2)O_(2)稳定剂对H_(2)O_(2)漂白的稳定性能,并与进口稳定剂进行比较。结果表明,新型H_(2)O_(2)稳定剂对Fe^(3+)、Mg^(2+)、Mn^(2+)、Ca^(2+)的螯合能力分别达262.3、105.2、141.4、160.3 mg/g;在模拟国内4个地区水质中不同金属离子含量条件下,新型H_(2)O_(2)稳定剂能够有效抑制H_(2)O_(2)分解,具有与进口产品相当的稳定能力。在纸浆漂白工艺条件下,新型H_(2)O_(2)稳定剂在低用量时,对桉木化机浆、杨木化机浆、蔗渣化机浆和芦苇化机浆的漂白均有良好的稳定效果。

魔芋多糖基活化剂在棉织物低温漂白中的应用

以自制魔芋多糖基活性剂作为棉织物过氧化氢低温漂白助剂,研究漂白工艺条件对漂白效果的影响,优化漂白工艺并阐述其活化机理。结果表明,优化漂白工艺为:活化剂4 g/L,NaOH 50 mmol/L,温度70℃,时间60 min;漂白活化剂能促进羟基自由基(HO·)的产生,有效降低漂白温度。成本计算结果表明,使用漂白活化剂能从试剂消耗和能源消耗两方面显著降低生产成本。

纯棉无纺布低温近中性练漂体系构建及其工艺优化

纯棉无纺布练漂在高温强碱中进行,能耗高、排污大、纤维损伤严重。针对该问题,试验构建了三种低温近中性练漂体系,通过对比三者练漂无纺布的颜色特征值、亲水性能和机械性能,选出最优体系;采用XRD、FT-IR、SEM分析体系对棉纤维微观结构与形貌的影响;通过中心复合设计(CCD)优化该体系漂白工艺,并寻求影响织物白度(WI)的关键因素。研究表明:四乙酰乙二胺/过氧化氢(TAED/H2O2)体系练漂织物WI最高,亲水性优良,强力损伤最小(<20%);练漂体系对棉纤维晶型结构与官能团无影响,能有效去除纤维表面杂质,保护纤维不受损伤。CCD结果显示,温度对WI影响最显著,其次是H2O2浓度与NaHCO3浓度;在最优条件下,得到的理论最优WI为90.38,比原布WI高39.32%。

比较两种漂白剂髓室内漂白后对牙体抗力的影响

目的 比较过氧化氢(HP)与过硼酸钠(SP)在髓室内漂白后对牙体抗力的影响。方法 40颗进行根管治疗的完整离体前磨牙,随机分为HP组、SP组、SP+HP组、对照组,每组10颗。对照组进行水处理、HP组进行过氧化氢处理, SP组进行过硼酸钠处理, SP+HP组进行过氧化氢+过硼酸钠处理。四组牙齿均建立体外髓室内漂白模型,最后置于万能试验机上测试最大载荷,记录每个样本最大承受压力。比较四组牙齿的抗力值。结果 HP组、SP组、HP+SP组抗力值分别为(868.37±94.47)、(796.07±32.88)、(1072.09±56.34)N,均低于对照组的(1244.17±98.40)N,差异有计学意义(P<0.05)。HP组与SP组抗力值比较,差异无统计学意义(P>0.05)。HP+SP组抗力值高于HP组及SP组,差异有统计学意义(P<0.05)。结论 过氧化氢及过硼酸钠用于髓室内漂白均会降低牙体抗力,过硼酸钠更为显著,但两者联合时对牙体抗力的影响变小。

烷基苯磺化产生的黑磺酸精制回收技术研究

利用硫酸钠水溶液对膜式磺化器生产磺酸的过程中产生的黑磺酸进行水解,分离析出硫酸后再用过氧化氢在活化剂的作用下进行漂白处理,考察了硫酸钠溶液浓度、用量以及漂白剂用量、漂白温度、漂白时间等因素对漂白效果的影响。结果表明,优化处理条件为:以质量分数为8%的硫酸钠水溶液为水解剂,硫酸钠溶液加量为黑磺酸质量的10%,反应温度40~42℃,搅拌30 min后静置分层,硫酸分离效果最佳;漂白反应采用质量浓度为30%的双氧水为漂白剂,双氧水加量为黑磺酸质量的7%,漂白活化剂采用异壬酰氧苯磺酸钠,加量为双氧水质量的1.5%,漂白温度50℃,漂白时间2 h。在此条件下,黑磺酸的色泽由大于1 000 Kllet下降到173 Kllet,黑磺酸中硫酸质量分数由17.09%下降至5.01%。该技术可以应用于工业和民用洗涤剂的生产。

用于化机浆过氧化氢漂白的几种新型稳定剂的性能比较

本研究探讨了3种稳定剂(LS-8838、SB-005和KML)替代传统Na2 SiO_(3)用于化机浆过氧化氢漂白的可行性及优缺点,优化了漂白稳定剂的使用条件,比较了3种漂白稳定剂与Na2 SiO_(3)在过氧化氢漂白过程中的结垢现象。结果表明,针对未漂杨木化学机械浆进行过氧化氢漂白,当NaOH用量3%、H_(2) O_(2)用量5%、漂白时间60 min时,漂白稳定剂(LS-8838、SB-005、KML)的最佳使用条件均为添加量0.3%、浆浓25%,漂白温度80℃。3种漂白稳定剂添加量为0.3%的漂白效果均能达到Na2 SiO_(3)添加量为1.5%的漂白效果,纸浆白度分别为75.4%、76.4%、74.4%;与Na2 SiO_(3)漂白相比,残余H_(2) O_(2)含量分别提高了62.5%、135.4%和87.5%;纸张抗张指数分别提高了14.3%、18.6%、0.6%。其中SB-005处理过的纸浆白度、纸张抗张强度最佳,但其硅含量较高,结垢现象比较严重;无磷低硅LS-8838与含磷无硅KML的漂白效果(残余H_(2) O_(2)含量、白度、强度)也优于Na2 SiO_(3)的漂白效果,其中LS-8838漂白效果最佳且无结垢现象,可作为Na2 SiO_(3)的替代品。

新型脱色方法对烷基糖苷脱色效果的影响

通过一步法合成烷基糖苷后,在漂白时采用强力自吸多相流泵,使漂白体系从常规的搅拌体系变成循环体系,对采用此新型脱色方法和普通方法的漂白过程中的现象进行分析,并对漂白产品的检测数据进行对比.考察了新型脱色方法的温度、pH及泵的参数变化对产品的影响,得到了最佳的漂白脱色条件:脱色温度控制在70~80℃,pH控制在12左右,泵的流量控制在40 m3/h。上述条件下,得到的产品色泽浅、质量好。

弱碱性过氧化氢漂白对杨木CTMP中碳水化合物和木质素的影响

本研究探讨了杨木CTMP碱性过氧化氢漂白中,MgO取代NaOH比例和漂白时间对杨木CTMP中碳水化合物和木质素含量及纸浆性能的影响。结果表明,在漂白初期,杨木CTMP中的碳水化合物和木质素溶出较快,漂白后期溶出的速率较缓慢。随MgO取代NaOH比例的增加,杨木CTMP的漂白得率显著提高,漂白浆中的碳水化合物和木质素含量明显增加。与对照样(以NaOH为碱源)相比,漂白时间90 min,MgO取代NaOH比例为75%时,漂白浆中的综纤维素和木质素含量分别达67.60%和23.09%;浆张的松厚度从2.09 cm^(3)/g上升到2.21 cm^(3)/g,增加了5.74%;白度略微下降;浆张的抗张指数和撕裂指数分别下降了14.16%和14.32%,达40.6 N·m/g和3.47 mN·m2/g。

汉麻浆全无氯漂白工艺研究

用于生产卷烟纸的汉麻麻皮纤维含量高、易漂白,但是残留在麻皮中的麻秆木素含量高,不易漂白,在全无氯漂白中会产生纤维性尘埃。本文研究了“高温高p H值下H2O2强化的碱抽提(Ep)-螯合预处理(Q)一段H2O2漂白(P1)二段H2O2漂白(P2)”四段漂白技术用于汉麻浆漂白的可行性,发现白度可以达到85%以上,但是无法彻底解决由麻秆产生的尘埃问题。在P1段加入乙酸使之变为乙酸和H2O2混合漂白(A P),将漂白工艺改良为Ep(A P)P三段漂白工艺的实验结果显示,可以彻底解决由麻秆产生的尘埃问题,且纸浆白度可达到88%以上。此工艺方案无需利用特殊漂白设备,采用现有的CE M P等含氯漂白工艺设备即可实现,为目前麻浆厂漂白工段升级改造成全无氯漂白提供了有效的方法。

棉针织物高白度、低强损冷轧堆漂白工艺研究

针对棉针织物常规冷轧堆漂白工艺处理后白度值不高、织物损伤大的问题,文中主要考察活化剂R60用量、漂白增效剂CF-15用量、NaOH用量、H_(2)O_(2),用量、蒽醌用量、堆置时间、堆置温度对棉针织物漂白效果的影响,确定棉针织物高白度、低强损冷轧堆漂白工艺的最佳工艺条件,并与常规冷轧堆漂白工艺的处理效果进行对比。结果表明:高白度、低强损冷轧堆漂白最佳工艺为活化剂R60用量4g/L、漂白增效剂CF-15用量3g/L、NaOH用量20g/L、H_(2)O_(2),用量100mL/L、蒽醌用量10g/L、堆置时间24h、堆置温度为25℃,处理后棉针织物的白度为83.35、30min毛效为10.7cm、强降率为1.32%.

羊绒纤维H_(2)O_(2)-TAED活化体系低温漂白工艺

采用H_(2)O_(2)-TAED活化漂白体系对羊绒纤维进行低温漂白研究。以漂白后纤维的白度和断裂强力为评价指标,探讨了H_(2)O_(2)用量、TAED用量、pH值、温度和时间对羊绒纤维漂白效果的影响,开发了在近中性和较低温度下的羊绒氧漂工艺。结果表明,在30%H_(2)O_(2)用量60%~80%、TAED用量0.5 g/L、pH值8、温度60℃、时间50 min的条件下漂白羊绒可获得良好的漂白效果;与常规工艺相比,TAED的加入能有效提升羊绒纤维的白度,减少强力损伤,降低漂白温度。

磨除表层牙釉质对冠内漂白后牙釉质粘接强度的影响

目的 探讨磨除表层牙釉质对冠内漂白后牙釉质与树脂水门汀粘接强度的影响。方法 选择离体小牛前牙制备48个牙体组织块(长4 mm、宽4 mm、厚4 mm),树脂包埋,根据是否进行冠内漂白随机分为2组:漂白组(B)、无漂白组(NB)。B组使用40%过氧化氢漂白剂对牙本质面进行处理,NB组不做漂白处理。于牙釉质面磨除0.5 mm以模拟贴面牙体预备,将树脂柱(直径1 mm、高1 mm)粘接于釉质面。依据是否对试件进行冷热循环,将B及NB组分为2个亚组(n=12):冷热循环组(T)、无冷热循环组(NT)。T组进行5000个周期冷热循环,NT组不进行冷热循环。使用万能材料试验机进行微剪切粘接强度(micro-shear bond strength,μSBS)测试,体视显微镜下观察断裂模式及断裂界面,采用SPSS软件对实验数据进行双因素方差分析。结果 4个处理组的μSBS值分别为BT组(21.10±5.18)MPa、BNT组(21.85±7.08)MPa、NBT组(22.10±6.38)MPa、NBNT组(25.21±5.83)MPa,4组间的差异无统计学意义(P>0.05)。混合断裂是最常见的断裂模式,其次是界面断裂和内聚断裂。结论 使用40%过氧化氢进行冠内漂白后,通过磨除表层0.5 mm的牙釉质,可获得良好的牙釉质粘接性能。

表面活性剂在活化氧漂体系去除纺织品有色污渍中的作用

纺织品在使用过程中经常会沾染一些有色污渍,在家庭洗涤中使用普通洗涤配方很难将其有效去除。过氧化物经常被用于家庭洗涤中去除纺织品沾染的有色污渍,但需在较高温度下起作用。活化氧漂体系是通过向过氧化物溶液中加入漂白活化剂形成的漂白体系,能够在较低温度下将纺织品有色污渍有效去除。本文使用N-[4-(三乙基铵甲撑)苯酰基]己内酰胺氯化物(TBCC)和四乙酰乙二胺(TAED)为漂白活化剂构建活化氧漂体系,以十二烷基苯磺酸钠(SDBS)和十八烷基三甲基氯化铵(STAC)为表面活性剂,设计洗涤配方,研究其在室温近中性条件下去除纺织品有色污渍的性能。实验结果表明:表面活性剂自身不能有效去除纺织品有色污渍,但携带的离子电荷能够在一定程度上影响活化氧漂体系对纺织品有色污渍的去除性能,SDBS与TBCC活化氧漂体系组成的洗涤配方能够在室温近中性条件下有效去除纺织品上的有色污渍。