Coagulation removal of melanoidins from biologically treated molasses wastewater using ferric chloride

The pigments (melanoidins) in molasses wastewater are refractory to conventional biological treatment. Ferric chloride was used as coagulant to remove color and chemical oxygen demand (COD) from molasses effluent. Using jar test procedure, main operating conditions such as pH and coagulant dosage were investigated. Under the optimum conditions, up to 86% and 96% of COD and color removal efficiencies were achieved. Residual turbidity in supernatant was less than 5 NTU and Fe3+ concentration was negligible because of effective destabilization and subsequent sedimentation. The results of high performance size exclusion chromatography (HPSEC) show that low molecular weight (MW) fraction of melanoidins is more reactive than high MW fraction and increase in the concentration of the lowest MW organic group is related to the capacity of charge neutralization. Aggregate size measurement reveals the size effect on the settleability of flocs formed, with larger flocs settling more rapidly. Charge neutralization and co-precipitation are proposed as predominant coagulation mechanism under the optimum conditions. (C) 2009 Elsevier B.V. All rights reserved.

Effects of polyaluminum chloride and copper sulfate on phosphorus and UV254 under different anoxic levels

Experimental sediments and water from shallow, eutrophic Dianchi Lakes were treated in a controlled laboratory microcosm using different chemicals under different anoxic levels. This study revealed that the polyaluminum chloride (PAC) was able to inhibit the phosphorus release and decrease the UV254 value at any anoxic level. When the DO concentrations were between 0.76-0.95 mg(.) L-1, the UV(254)value, total phosphorus (TP), and total dissolved phosphorus (TDP) in the water column were decreased by 71.93%, 87.12% and 64.24% respectively. The UV254, TP, and TDP were also decreased by 72.94%, 70.87% and 50.76% respectively at the levels of 4.56-5.32mg(.)L(-1) of DO concentrations. The treatment effects of TP and TDP in the water column using copper sulfate however were not as efficient as the PAC treatment. The UV254 value was increased with the addition of copper sulfate at every anoxic level tested but the chlorophyll-a (Chl-a) content was decreased rapidly and efficiently by copper sulfate more than the treatment by PAC. When the DO concentrations were 0.76-0.86mg(.)L(-1) and 4.75-5.14mg(.)L(-1), the Chl-a concentrations were decreased by 84.87% and 75.07% respectively through copper sulfate treatment. With additions of PAC and copper sulfate, the phosphorus fractions in sediments were shifted forward to the favorable shapes that have little ability of release. The TP concentrations in sediments were increased after treatment via PAC and copper sulfate. Under anoxic conditions, most of the BD-P (Fe-P) to NaOH-P (Al-P) was converted using the recommended PAC dose in BD-P rich sediment. Similar to the PAC, the copper sulfate also could flocculate the exchange phosphorus from sediment to overlying water. Overall though, the effects of copper sulfate treatment were not better than that of the PAC.

遥爪丁腈共聚物的增韧环氧－聚氨酯IPN及PVC共混物的合成与表征

Ⅰ. 增韧环氧／聚氨酯互穿网络聚合物的合成与表征 用部分环氧树脂与丁腈羧反应，进行端基转化，制得端环氧基丁腈－环氧共聚物与环氧树脂的混合物，经叔胺固化后，得到增韧环氧（TEpx）。制备了两种IPN体系，体系1为增韧环氧／蓖麻油聚氨酯IPN，体系2为增韧环氧／聚醚聚氨酯IPN。用红外光谱研究了动力学，研究结果是，对于体系1，－OH基与－NCO基的反应速度大于环氧基的聚合速度，因此，IPN体系中，PU网络的形成比环氧网络快。环氧上的－OH基与蓖麻油上的羟基相似。同属伸羟基，它也会与－NCO基反应，因此，所形成的IPN的两网络间，存在着一定程度的化学交联。在增韧环氧的分子结构中，含有丁腈羧低聚物链段，使得增韧环氧与蓖麻油聚氨酯的相容性较好，该因素对这种IPN形态结构的形成，是很重要的，从动态力学性能的测试结果，能说明这个问题，即玻璃化转变峰很宽，在一定组成时，半峰宽几乎达100 ℃。对于体系2，聚氨酯相起反应的羟基是伯羟基，它与－NCO基的反应速度比环氧中的羟基与－NCO基的反应速度大得多。此外，体系中的两组分，即增韧环氧与聚醚聚氨酯的相容性不好，反应速度的差别与相容性的差别，均将导致反应体系中相分离程度的增大。这在tanZ-T曲线上表现得很明显，出现了两个相距甚远的玻璃化转变峰。利用透射电子显微镜对两个IPN体系进行了形态观察，这些IPN具有特殊的结构，既有增韧环氧所存在的两相结构，又有IPN的两相结构。Ⅱ. 聚氯乙烯－丁腈羟低聚物共混物的合成与表征 制备了高聚物（PVC）－低聚物（HTBN）共混物，研究了该共混物的力学性能，阻尼性能及形态结构。研究结果表明，在HTBN中，丙烯腈含量较高时，随着HTBN加入量的增加，PVC的阻尼峰均有不同程度的加宽加高。在力学性能方面，共混物的抗张强度、伸长率也随低聚物中丙烯腈含量的高低而变化，丙烯腈含量较高时（25％，36％），随HTBN加入量的增加，性能变化不大，而丙烯腈含量较低时（15％，5％），当HTBN的加入达一定量时，性能发生突降。这些现象的出现，主要与相容性有关，HTBN中丙烯腈含量高，极性大，与PVC混溶性好，因而阻尼性能、力学性能均好。而HTBN中丙烯腈含量低，与PVC之间的粘合力不好，即混溶性不好，因而共混物性能不好。由TEM照片看，该共混体系的形态结构为细胞状结构，细胞内存在着界面模糊的两相结构，在低丙烯腈含量（15％）时，存在着部分界面清晰的两相结构，形态观察的结果与性能测定的结果一致。

THEORETICAL TREATMENT OF A3B5 CHLORIDE VAPOR-PHASE EPITAXY - GROWTH, DOPING, OPTIMIZATION

A theoretical description of chloride vapour-phase epitaxy (CVPE) has been proposed which contains two-dimensional (2D) gas-dynamic equations for transport of reactive components and kinetic equations for surface growth processes connected by nonlinear adiabatic boundary conditions. No one of these stages is supposed to be the limiting one. Calculated variations of growth rate and impurity concentrations along the growing layer fit experimental data well.