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1、 西安建筑科技大学硕士学位论文 剪切力场下不同分子量级别腐殖酸铝盐絮凝体形态学研究 专 业：环境科学环境科学 硕 士 生：张 坤张 坤 指导教师：金鹏康 教授金鹏康 教授 摘 要 论文以湖泊底泥为原料，采用 IHSS 推荐方法提纯底泥得到天然腐殖酸，通过元素分析(EA)提纯的腐殖酸主要由 C、 O、 N、 H、 S 等元素组成， 约占总量的 98%。采用超滤法对腐殖酸进行分子量分级，并进行有机碳质量衡算，结果表明，腐殖酸中分子量大于 30000 的物质最多，约占总量的 41%，分子量小于 1000 的物质最少， 约占总量的 6.7%， 分子量为 1000030000、 500010000、 3
2、0005000、 10003000这 4 个级别中物质量相差不大，分别约占总量的 11.5%、13.3%、11.8%和 15.7%。 以硫酸铝作为混凝剂，通过显微摄影、图像解析和粒子测速等方法测定铝盐絮凝体的粒径、沉速，计算出相应的分形维数和强度，运用分形理论讨论了剪切力场下不同分子量级别腐殖酸混凝形成的铝盐絮凝体结构特征。结果表明，絮凝体的分形维数随腐殖酸分子量的减小而降低，弱酸性(pH=5.0)条件下，分子量大于30kDa、10kDa30kDa 、5kDa10kDa 这 3 个级别絮凝体分形维数的范围分别为1.831.94、1.81.87、1.741.81；而在中性(pH=7.0)条件下，
3、3 个级别絮凝体分形维数分别在 1.771.78、1.771.83、1.711.78 之间。 弱酸性条件下，腐殖酸絮凝体的分形维数随铝盐投加量的增加呈现先增大后减小，然后再增大并最终稳定的趋势，铝盐投加量为 0.2mg-Al/mg-TOC 时分形维数最大，约为 1.93；中性条件下，腐殖酸絮凝体的分形维数随铝盐投加量的增大而增大并最终达到稳定，铝盐投加量为 1.5mg-Al/mg-TOC 时分形维数最大，约为1.87。总体而言，弱酸性条件下絮凝体的分形维数大于中性条件下铝盐絮凝体的分形维数。pH=5.0 时，絮凝体的分形维数和絮凝体强度及沉降速度正相关，和絮凝体的平均粒径反相关，而在 pH=7
4、.0 时絮凝体的分形维数和其平均粒径也存在一定的正相关关系。 不同分子量级别的腐殖酸絮凝体分形维数随着剪切力的改变而表现出相似的变化规律，即随着剪切力的增加，絮凝体分形维数缓慢增大，在临界破碎点出现本研究得到国家自然科学基金项目(50978211)的资助 西安建筑科技大学硕士学位论文 最大值，然后减少，并最终趋于稳定。腐殖酸分子量大于 30kDa 级别中混凝反应的最佳剪切条件一般为 G=120s-1或 G=150s-1；腐殖酸分子量在 10kDa30kDa 时，G=90s-1时絮凝体即开始破碎；而对于腐殖酸分子量 5kDa10kDa 级别来说，G=90s-1时絮凝体开始破碎的现象更多，说明剪切
5、力变化对低分子量级别中形成的絮凝体影响更显著。 关关 键键 词词：腐殖酸；分子量分级；分形维数；絮凝体强度；形态特征 论文类型论文类型：基础研究 西安建筑科技大学硕士学位论文 Study on the morphology Al-humic flocs under different molecular weight distribution in shear force field Speciality: Environmental Science Author: Zhang Kun Adviser: Prof. Pengkang Jin ABSTRACT This paper select
6、ed lake bottom sediment as raw material, the use of IHSS recommended method for purification of the sediment to obtain natural humic acid,humic acid purified by means of elemental analysis(EA) is mainly composed of the elements of C,O,N,H,S,about 98% of the total mass of humic acid. By ultrafiltrati
7、on and organic carbon mass balance calculations to separate the humic acid of different molecular weight, the results show that the humic substances which molecular weight greater than 30000 up to about 41% of the total molecular weight,and the substances of molecular weight less than 1000 at least,
8、accounting for 6.7%of the total.Substances of four molecular weight level of 1000030000、500010000、30005000、10003000 account for 11.5%,13.3%,11.8%,15.7% of the total respectively. Determination of aluminum flocs size,settling velocity and other parameters to calculate the fractal dimension and streng
9、th through microscopic photography, image analysis and particle image velocimetry, and use the fractal theory to discuss the structural characteristics of humic flocs which formation in the cogulation with aluminum sulfate as coagulant and humic acid of different molecular weight level under the she
10、ar force field.The results show that the fractal dimension of flocs decrease with the molecular weight decreases.Under the conditions of weakly acidic(pH=5.0),the range of flocs fractal dimension of three level which molecular weight greater than 30kDa,10kDa30kDa ,5kDa10kDa was 1.831.94,1.81.87,1.74
11、1.81 respectively, but the value was ranging from 1.77 to 1.78,1.77 to 1.83,1.71 to 1.78 respectively at neutral (pH=7.0). Under weakly acidic conditions,the change of HA flocs fractal dimension with the increase of aluminum dosage showing the trend of first increses and then decreases, 西安建筑科技大学硕士学位
12、论文 then increases and finally stable, and the maximum value approximately 1.93 at aluminum dosage was 0.2mg-Al/mg-TOC; The fractal dimension of humic acid flocs increases with increasing aluminum dosage gradually and eventually and reach a steady value at pH=7.0,the maximum at 1.5mg-Al/mg-TOC of alu
13、minum dosage is about 1.87.Overall,the fractal dimension of floc at weakly acidic is greater than the value at neutral. At pH=5.0,the flocs fractal dimension, strength and settling velocity are positively correlated and inversely related the average particle size of flocs,but there is a certain posi
14、tive relationship between flocs fractal dimension and average particle size at pH=7.0. HA flocs fractal dimension of different molecular weight showed similar variation with the change of shear force,the flocs fractal dimension slowly increase with the increase of the shear force,and the maximum at
15、the critical broken point,and then the value decreased,and eventually stabilized. The best shear force of coagulation with humic acid which molecular weight greater than 30kDa are generally G=120s-1 and G=150s-1;At the humic acid molecular weight was ranging from 10kDa to 30kDa, the flocs began brok
16、en at G=90s-1;For the humic acid molecular weight level of 5kDa10kDa,the phenomenon of flocs broken increased at G=90s-1,this shows that the shear force changes more significant impact on floc which formed in coagulation with lower molecular weight hunic acid. Keywords:humic acid,molecular weight distribution,fractal dimension,floc strength, morphological characteristics Paper type: Fundamental study 西安建筑科技大学硕士学位论文 I目 录 1 绪论绪论 .
