Influence of chitosan characteristics on the coagulation and the flocculation of bentonite suspensions

Ten chitosan preparations with different molecular weights (MW) and degrees of deacetylation (DD) were tested for coagulation of 5 g L(-1) bentonite suspensions at pH 5 and 7 in demineralized water (DW) and in tap water (TW). Coagulation was better in TW than in DW for every condition and lower doses of chitosan were required at pH 5 than at pH 7. More than 95% of residual turbidity (after sedimentation in the absence of chitosan) was removed using less than 0.10 mg L(-1) chitosan in either TW or DW at pH 5 or in TW at pH 7. Higher doses were required for removal of turbidity in DW at pH 7, but in all cases the effective concentrations of chitosan were much lower than required for complete neutralization of the negative charge on the bentonite particles. Removal of turbidity was best for the higher MW chitosans in either the B series (89.5% DD) or the C series (95% DD) of chitosans. Overall, the results were consistent with destabilization of bentonite by the combined mechanisms of electrostatic patch and bridging. The improved performance of chitosan in TW could have been due to improved attachment to bentonite due to the presence of sulfate and other counter-ions in TW.     

粉煤灰负载钒氧化物低温SCR催化剂脱硝性能研究

目前,我国电厂普遍采用SCR法高含尘工艺对烟气中的NOx进行脱硝,催化剂存在严重堵塞、中毒等问题,SCR法低含尘工艺越来越引起重视。为了制备SCR法低含尘工艺中的低温SCR脱硝催化剂,本文将钒氧化物负载在粉煤灰和膨润土混合制成的复合材料载体上,制成V2O5/FA-BT催化剂,同时分别用全自动比表面及孔隙度分析仪(Micromeritics Tristar 3 000)和扫描电子显微电镜(SEM)对催化剂的比表面积和表面形貌进行表征。结果表明:不同V2O5负载量的V2O5/FA-BT催化剂在低温下有很好的脱硝效果,其中以V2O5负载量(质量分数)为11%的V2O5/FA-BT脱硝效果最好,当反应温度为130℃时,脱硝率达到89%;对催化剂进行酸改,CH3COOH酸改的催化剂比表面积较大且脱硝效果最好。     

膨润土对Pb~(2+)的吸附及铝的影响研究

研究膨润土对水溶液中铅的吸附特性以及铝对铅吸附的影响。通过各组吸附实验,建立膨润土对水溶液中铅离子的吸附最佳条件,天然膨润土对铅的吸附平衡时间约为60 min,其吸附符合一级动力学方程;铅吸附最适p H=9;天然膨润土对水溶液中铅离子的吸附规律符合Freundlich等温方程和Langmuir等温方程,呈显著相关性;加入少量铝离子时,吸附除铅能力增强,但继续增加铝浓度,去除能力降低,该现象主要通过铝盐水解所致的p H变化起调节作用,电中和作用不明显。     

钒钛铁精矿润磨试验研究

针对川威集团自产的钒钛铁精矿,在钒钛铁精矿、膨润土理化性能测定结果基础上,进行了钒钛铁精矿的润磨、成球试验研究,探究了该钒钛铁精矿较佳的润磨工艺参数。     

膨润土的铝酸脂表面改性研究

为提高无机膨润土与有机塑料的相容性,强化两者的复合效果,研究了铝酸脂对膨润土的偶联改性行为。以沉降体积和粘度为评价指标,考察了单次物料用量、改性温度、改性剂用量及改性时间等对膨润土改性效果的影响,并利用红外光谱分析探讨了铝酸脂对膨润土的改性机理。结果表明：铝酸脂偶联剂对膨润土的改性效果明显,较佳改性条件为改性温度110 ℃,改性剂用量3.0%,改性时间30 min;铝酸脂偶联剂对膨润土的改性同时存在化学吸附和物理包覆作用。     

我国膨润土资源概况及开发利用现状

葫芦岛市位于锦西-哈尔套膨润土成矿带的最南端,为探究葫芦岛膨润土的特性,对葫芦岛的6个膨润土矿进行了研究,通过测定试样的膨胀容、亚甲基蓝吸收量、阳离子交换容量和X射线衍射分析,对葫芦岛膨润土的表观特性、矿物组成、膨胀性能和阳离子交换性等性能进行了评价和表征。研究表明：葫芦岛膨润土矿均为钙基膨润土矿,总体质量较好,大部分膨润土的粒度均匀、自然白度较高,蒙脱石平均含量接近或高于70%。葫芦岛膨润土矿的石英、长石、方解石是主要脉石矿物,矿物组成比较简单,阳离子交换性能较好,在辽西地区膨润土矿中处于中上等地位,具有较强的代表性。然而,辽西膨润土普遍含有方石英,限制了产品的应用范围。     

超细膨润土/环氧树脂复合材料的结构与热性能

采用TG-DTA、IR、SEM、马丁耐热和Daniel流动点测定等方法,研究了有机胺改性超细膨润土与环氧树脂的固化体系的结构及其性能。结果表明,有机胺改性膨润土与环氧树脂固化复合后,可形成由层问固化与层外固化相结合的结构,所得复合材料的耐热性能、分散性均有提高,其中活化有机膨润土／环氧树脂复合体系的分散效果和马丁耐热特性改善更加显著。     

Case History of Damage to a School Building Caused by Differentially Heaving Bedrock

This case study considers the question of whether settlement or heave is the principal cause of damage to a school building near Denver. The building, which was underlain by engineered fill in the center and shallow claystone bedrock beneath the outer wings, experienced progressive deformation and significant damage during a 15-year period. With several millions of dollars of rebuilding costs at risk, the most likely cause of failure needed to be ascertained to arrive at an optimum mitigation solution. The investigation described herein considers the regional geology and its known effect on various types of engineered structures in terms of characteristic damage patterns. The focus progressively narrows to concentrate on the geology and damage patterns of the local area and the site. The findings indicate that the major cause of damage to the building is associated with differential heaving of steeply dipping, expansive bedrock layers. This conclusion was adopted as a basis for subsequent remedial planning and design.     

Enzyme immobilization: Part 2: Immobilization of alkaline phosphatase on Na-bentonite and modified bentonite

Alkaline phosphatase from calf intestinal mucous membrane was immobilized on unmodified and modified bentonites. The activity of the immobilized enzyme was examined under varying experimental conditions. The effects of various factors such as concentration of enzyme solution, pH and temperature, stirring and various thermodynamic parameters were evaluated. The highest enzyme activity, for free and immobilized enzyme, was obtained in 0.1 M phosphate buffer at pH 7. Optimal enzyme activity of both free and adsorbed enzyme was reached at pH = 10. The best time period of magnetic stirring was 2 h at 4 °C. The adsorption isotherm was modeled by Langmuir equation. The effect of substrate concentration on enzymatic activity of the free and immobilized enzymes showed a good fit to the Michaelis–Menten plots. The immobilized enzyme exhibited activity comparable to the soluble enzyme after storage at 30 °C. Thermal stability and resistance against proteolytic attack were also evaluated.     

Adsorption of copper and lead in aqueous solution onto bentonite modified by 4'-methylbenzo-15-crown-5

The adsorption of heavy metal ions (Cu2+ and Pb2+) onto organobentonite modified by 4'-methylbenzo-15-crown-5 (MB15C5) from bentonite compared with natural bentonite (N-Bentonite) is described in this paper. The kinetic parameters of the models are calculated and discussed, and closely fitted a pseudo-second-order model in all cases. For bentonite modified with MB15C5 (MB15C5-Bentonite) and N-Bentonite, the equilibrium data closely fitted the Langmuir model and showed the following affinity order: Pb2+ > Cu2+, and the adsorption capacity of MB15C5-Bentonite is higher than that of N-Bentonite for Pb2+ and Cu2+. The effect of pH is examined over the range 1.5-6. The adsorption of Cu2+ and Pb2+ increases with increasing pH and the adsorption of Cu2+ and Pb2+ reaches a maximum at pH 3.5-6.