Coagulation rate studies of spinnable chitosan solutions

The coagulation properties of some mixtures of 5% chitosan in 2% aqueous acetic acid were investigated with the goal of determining the optimal coagulation conditions for the spinning of chitosan fibers. The chitosan was characterized and found to possess a deacetylation value of 84.9 ± 0.2%. Molecular weight of the chitosan was also measured; based on intrinsic viscosity, the M_v value was 7.73 × 10⁵ g mol⁻¹, and based on high-pressure liquid chromatography, the M_w value was 1.14 × 10⁵ g mol⁻¹. Solutions of 5% chitosan/2% acetic acid were prepared, filtered, and extruded through a large-diameter hole syringe into coagulation baths of varying composition that were all strongly basic in nature, at least a pH of 12 or greater. For each coagulant, time was varied from between 22 s and 2 minutes at room temperature. A second set of experiments was conducted where the temperature was varied from 20°C to 70°C at a constant time of 45 s. In a third set of experiments, using a 1M NaOH coagulant, different chitosans were also analyzed. Throughout all of the experiments, a distinct moving boundary between coagulated and uncoagulated polymer was observed within the cylindrical-shaped polymer fibers. Using a series of equations based on Fick's 2nd Law, a straight line relationship has been demonstrated between boundary motion and time and between boundary motion and temperature for each coagulant tested. The activation energy for each coagulant was also determined. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 117–127, 1997     

Coagulation–flocculation of colloidal suspensions of kaolinite,bentonite, and alumina by chitosan sulfate

This article reports on the removal of colloidal suspensions of kaolinite, bentonite, and alumina using chitosan sulfate (ChS). ChS was synthesized by partial introduction of sulfate groups in the chitosan (Ch) structure. The polyampholyte (chitosan sulfate) shows variable charge depending on the pH of the solution. ChS was characterized by FTIR, ¹³C‐NMR, elemental analysis, and potentiometric titrations. The ChS coagulation–flocculation capacity for kaolinite, bentonite, and alumina aqueous suspensions was systematically studied. The coagulation–flocculation process was carried out at various pH values and ChS concentrations. The pH range in which the largest ChS removal capacity was observed depended on particle type (4.5–5.5 for kaolinite, 4.5–7.0 for bentonite, and 7.0–8.0 for alumina). The removal of colloidal particles is explained by charge neutralization due to electrostatic interactions between ChS and particles and particle entrapping when the polyelectrolyte precipitates. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

混凝-吸附联合处理含铬废水的研究

采用新型混凝剂聚磷氯化铝铁(PPAFC)对含铬废水进行混凝处理;再采用铝化改性膨润土对含铬废水进行吸附处理。结果表明:在PPAFC 40mg/L,铝化改性膨润土2.0g/L,室温的条件下,总铬的去除率超过99.8%,出水中总铬的质量浓度达到《电镀污染物排放标准》(GB 21900-2008)要求。     

Chitosan Coagulation Pretreatment to Enhance Ceramic Water Filtration for Household Water Treatment

Viruses are major contributors to the annual 1.3 million deaths associated with the global burden of diarrheal disease morbidity and mortality. While household-level water treatment technologies reduce diarrheal illness, the majority of filtration technologies are ineffective in removing viruses due to their small size relative to filter pore size. In order to meet the WHO health-based tolerable risk target of 10⁻⁶ Disability Adjusted Life Years per person per year, a drinking water filter must achieve a 5 Log₁₀ virus reduction. Ceramic pot water filters manufactured in developing countries typically achieve less than 1 Log₁₀ virus reductions. In order to overcome the shortfall in virus removal efficiency in household water treatment filtration, we (1) evaluated the capacity of chitosan acetate and chitosan lactate, as a cationic coagulant pretreatment combined with ceramic water filtration to remove lab cultured and sewage derived viruses and bacteria in drinking waters, (2) optimized treatment conditions in waters of varying quality and (3) evaluated long-term continuous treatment over a 10-week experiment in surface waters. For each test condition, bacteria and virus concentrations were enumerated by culture methods for influent, controls, and treated effluent after chitosan pretreatment and ceramic water filtration. A > 5 Log₁₀ reduction was achieved in treated effluent for E.coli, C. perfringens, sewage derived E. coli and total coliforms, MS2 coliphage, Qβ coliphage, ΦX174 coliphage, and sewage derived F+ and somatic coliphages.     

水厂混凝设备的选用和改造实践

本文简要叙述了给水处理中混凝的基本原理,并简单介绍了本单位如何选用混凝构筑物及其改造实践。     

壳聚糖对银杏叶水提液的絮凝工艺研究

采用天然高分子絮凝剂壳聚糖对银杏叶水提液进行絮凝提取,其目的是优化生产工艺,提高药液的澄清度和药液质量。实验利用光的吸收和散射定律,以絮凝率和总黄酮损失率为衡量指标,判断不同影响因素对絮凝效果的影响,并将其与醇沉工艺的提取方法进行比较。结果通过单因素实验先判断出有利于絮凝的趋势,之后又利用正交实验确定了絮凝的最佳工艺条件:絮凝剂质量浓度1.071 g/L,絮凝温度40℃,体系pH值4.9。并且得出壳聚糖对银杏叶水提液的絮凝工艺效果明显优于醇沉法。     

水溶性壳聚糖及磁性壳聚糖微球的制备

以废弃蟹壳为原料制备出了高脱乙酰度壳聚糖和脱乙酰度50%的水溶性壳聚糖,通过电位滴定、红外光谱等对产物的脱乙酰度、功能基团作了表征,测定了产物的黏度,结果表明制备的水溶性壳聚糖的动力黏度为82.9 mPa.s。以0.01 mol/L硝酸钴和0.02 mol/L硝酸铁的混合溶液,采用微乳液法制备了纳米铁酸钴,以水溶性壳聚糖为原料制备了壳聚糖/纳米铁酸钴复合微球,TEM结果显示该磁性壳聚糖微球为规则球形,粒径13μm左右,分散性好。     

助凝剂在冬瓜山铜矿全尾充填絮凝沉降中的运用

选厂产出的20％左右低浓度的极细粒级全尾砂浆直接进入立式砂仓,根据全尾砂物理力学及电化学特性,选择新型高效廉价化学添加剂,实现全尾砂在砂仓内快速沉降浓缩连续造浆.全尾砂沉降速度是自然沉降速度的10倍以上,且上部溢流水质清亮,能够达到国家排放标准,该工艺浓缩成本低、仓底不板结、造浆浓度稳定、系统制备能力大、强度高、投资小,从根本上解决了全尾砂应用中的难题.     

Fenton氧化与混凝法联合预处理煤化工废水

以煤化工废水的总酚、COD、氨氮和浊度为评价指标,通过单因素试验分别考察了Fenton试剂、Fenton试剂联合聚合硫酸铝铁(PAFC)、Fenton试剂联合PAFC与阳离子型聚丙烯酰胺(CPAM)联合预处理煤化工废水的总体效果,并探究了联合处理方法降解煤化工废水的机制。结果表明,Fenton氧化联合混凝法处理煤化工废水的效果明显最优,废水预处理后的CODCr、NH3-N、总酚和浊度分别由3900、760.7、540 mg/L和28 NTU,降至2950、600.4、359.7 mg/L和5.3 NTU。另外,可生化性(BOD5/CODCr)由原来的0.11提升到0.29。由此可见,Fenton氧化联合混凝法预处理煤化工废水将强氧化性-助凝-絮凝作用有效结合,可以提高水质净化效果,大大降低后续的水处理负荷。     

H2O2存在下壳聚糖处理印染废水的实验研究

壳聚糖作为絮凝剂单独用于印染废水的处理效果不明显。研究了在H2O2存在下壳聚糖对不同染料模拟废水的处理效果,发现对于所述的5种染料,其处理效果都较好。以孔雀石绿模拟废水为例,研究了壳聚糖和H2O2的投加量、pH、脱色时间、温度等对处理效果的影响。结果表明,当m(H2O2)∶m(壳聚糖)为1.91∶1,pH为7,脱色时间为1 h,温度为40℃时,处理效果最佳,脱色率达到99%以上。     

水溶性壳聚糖的制备

以壳聚糖为原料,利用H2O2 NaClO在醋酸溶液中进行氧化降解反应,制备了水溶性壳聚糖。考察了H2O2和NaClO的浓度对壳聚糖降解率的影响,确定了最佳降解条件为:反应温度80℃,反应时间2h,H2O2和NaClO的浓度分别为5%和6%。利用红外和元素分析对产物进行了表征。     

壳聚糖在海水混凝处理过程中的助凝作用研究

将天然高分子絮凝剂壳聚糖(CTS)与无机絮凝剂FeCl3协同使用,混凝处理渤海湾近岸海水,考察了壳聚糖投加量、pH值和沉降时间对浊度和其它污染物去除效果的影响。试验结果表明,CTS对FeCl3助凝效果显著,与单独使用FeCl3相比,其浊度、化学耗氧量(CODMn)和总磷(TP)去除率分别提高了8.3%、9.6%和9.4%。FeCl3与CTS协同使用还可明显改善絮体的沉降性能,缩短沉淀时间。综合考虑各项主要技术指标,其海水混凝适宜条件为m(FeCl3)/m(CTS)=15.0。     

壳聚糖及其衍生物在工业污水处理中的研究及应用

介绍了近年来国内外壳聚糖及其衍生物在不同工业污水处理中的应用及相关机理.壳聚糖及其衍生物作为絮凝剂、金属离子的螯合剂以及有机物的吸附剂,在工业污水处理中有着相当广泛的应用,主要是絮凝和处理含重金属离子的工业废水,环境效益显著.壳聚糖及其衍生物是绿色的水处理剂,其未来发展的方向是合成性能更为优良的改性壳聚糖,与其他技术复合使用,并深入研究其对复杂工业废水的处理能力.     

Treatment of low turbidity water by sweep coagulation using bentonite

A novel strategy of sweep coagulation to treat low turbidity water is presented herein. Study findings demonstrated that an Na⁺‐saturated bentonite with medium cation exchange capacity (CEC) resulted in significant turbidity removal at a bentonite dosage of 30 mg dm^?3. Bentonite dispersion with fully delaminated platelets tended to undergo a more porous type of coagulation with intense face‐to‐face interactions of platelets and effectively entrapped TiO₂ particles in band‐type structures. This type of coagulation usually results in a large volume of settled flocs with a fluffy structure and excellent turbidity removal efficiency for sweep coagulation. The sign and magnitude of electrical charge on TiO₂ particles has a minor effect on the efficiency of sweep coagulation. Copyright © 2005 Society of Chemical Industry     

Biomedical applications and colloidal properties of amphiphilically modified chitosan hybrids

Chitosan is among the most abundant biopolymers on earth and has been either used or exhibited potential in a wide variety of industrial and biomedical applications. With the advancement of materials technologies, chitosan has been chemically modified to self-assemble into nanoarchitectures that are usable in advanced biomedical applications, such as drug nanocarriers, macroscopic injectables, tissue-engineering scaffolds, and nanoimaging agents. Colloidal amphiphilically modified chitosan (AMC) is a relatively recent material receiving increased attention with numerous publications addressing the medical advantages of specific systems. To date, many reviews have focused on the synthesis and biomedical properties of chitosan-based biomaterials, but a comprehensive study focusing on the colloidal properties of AMC in relation to biomedical performance appears to be lacking. This review provides a survey of the field, critically reviewing the colloidal properties and biomedical performance of AMC systems, such as nanoparticle drug delivery systems and macroscopic medical devices. Finally, the future development, market potential, and clinical implications of these promising colloidal-structured biomaterials are summarised.     

反相微乳液法制备纳米银/羧甲基壳聚糖复合微粒

采用反相微乳液法,以水合肼为还原剂制备纳米银/羧甲基壳聚糖复合微粒,并用红外光谱、X射线衍射、透射电镜对制备的样品微粒进行表征,讨论了搅拌速度、AgNO_3用量以及乳液体系的组成对纳米银复合粒子形貌与尺寸的影响。结果表明,当搅拌速度为1400r/min,AgNO_3用量为0.52g,吐温-80/液体石蜡体积比为4:5时,可制得粒径在50nm左右的纳米银/羧甲基壳聚糖复合微粒,且粒子具有较好的面心立方晶体结构。     

Chitosan for wastewater treatment

Chitosan (an amino‐polysaccharide obtained from deacetylation of chitin, the major constituent of crustaceous shells and insect cuticles) presents a cationic character in acidic media allowing its dissolution, its shaping and possible ion‐exchange interactions with anionic compounds (a property applied in adsorption and coagulation–flocculation processes). In neutral media, non‐protonated amino groups allow complexation of metal cations or organic chemicals. These different properties explain the interest taken by the scientific community in using this biopolymer. In solution it contributes to complex metals and their recovery by complexation‐assisted ultrafiltration. It can also be used to coagulate–flocculate organic compounds (as anionic dyes). In the solid state, it can be used for metal ion adsorption, as well as adsorption of organic compounds (dyes, pesticides, drugs, endocrine disruptors, etc.). The adsorption and coagulation–flocculation processes will be compared and examples considered. Moreover, it is noteworthy that the thermal degradation of this type of material is also more environmentally friendly than that of conventional synthetic resins (production of hazardous by‐products, etc.), a supplementary advantage of these biopolymer‐based sorbents. Combined with its ability to be chemically or physically modified improving the potential and phase separation of chitosan‐based materials, all these properties mean it is an excellent candidate for wastewater treatment. © 2017 Society of Chemical Industry     

壳聚糖季铵盐在混凝-微滤工艺中的应用研究

通过3-氯-2-羟丙基三甲基氯化铵(CTA)改性壳聚糖(CS)制备壳聚糖季铵盐(CS-CTA),并将其应用在混凝-微滤工艺中来研究其对出水水质和膜污染的影响。结果表明,在CS-CTA投加量为4 mg/L时,出水水质最好,此时UV254去除率为81.8%,浊度去除率为99%以上;在CS-CTA投加量为3 mg/L时,混凝出水引起的不可逆膜阻力最小,膜通量最高;与PAC相比,CS-CTA作为混凝剂能更有效地减缓膜污染。     

Enhanced Coagulation/Flocculation by Combining Diatomite with Synthetic Polymers for Oily Wastewater Treatment

The objectives are to evaluate the feasibility of treating oily wastewater using synthetic polymers (polyaluminum chloride (PAC), polyferric sulfate (PFS), and polyacrylamide (PAM)) combined with natural diatomite and to refine the operating parameters using diatomite as an adsorbent and a coagulant aid. The enhanced coagulation/flocculation by combining PAC with diatomite was investigated through mechanism analysis compared to the combination of PFS/PAM with diatomite, respectively. The effects of coagulant dose, initial pH, and settling time on chemical oxygen demand (COD) and turbidity were studied using PAC-diatomite in comparison with using PAC only. The enhanced coagulation/flocculation of diatomite with PAC was better than that with PFS/PAM in terms of COD/turbidity removal and floc settling characteristics, considering costs. The PAC-diatomite system reduced more than 70% of COD and 90% of turbidity over a wide pH range (7–10) within 20 min, with the optimum dose of PAC 50 mg/l and diatomite 1250 mg/l. The added diatomite effectively saved over 85% of PAC dose and simultaneously increased over 50% of COD removal efficiency. This study provided a novel and economical approach for diatomite utilization in the treatment of oily wastewater, satisfying the demands of reuse or reinjection into the ground.     

Effects of Slow-Mixing on the Coagulation Performance of Polyaluminum Chloride (PACI)

Conventional jar tests and on-line size monitoring were used to investigate the effects of slow-mixing intensity and duration on residual turbidity and floc size during charge neutralization coagulation and sweep flocculation with polyaluminum chloride. The compensatory effect of slow-mixing on coagulation performance following inadequate or excessive rapid-mixing was also examined. It is found that slow-mixing intensity has a more marked positive effect on charge neutralization coagulation than on sweep flocculation. The optimal root-mean- square velocity gradient, G, for slow-mixing is 15 s^-1 for both coagulation mechanisms, and charge neutralization coagulation requires a longer slow-mixing duration. The optimal slow-mixing duration, based on residual turbidity, is longer than the time to form the largest mean flocs. The optimal product of G and mixing duration, GT, for slow-mixing during charge neutralization coagulation (13500) are higher than that during sweep flocculation (4500) and both are less than the range of values recommended by the American Water Works Association (24000-84000). The optimal GT value under various slow-mixing conditions increases with G. Appropriate extension of slow-mixing duration during charge neutralization coagulation can improve coagulation performance after an inadequate or excessive rapid-mixing duration, but during sweep flocculation, appropriate shortening of slow-mixing duration after an excessive rapid-mixing or appropriate extension of slow-mixing duration after an inadequate rapid-mixing is favorable.