【作者】 陆泗进；

【导师】 刘凡；

【作者基本信息】 华中农业大学 ， 土壤学， 2004， 硕士

【摘要】 采取几种不同方法测定了酸性水钠锰矿、锰钾矿、碱性水钠锰矿、钙锰矿和黑锰矿电化学性质，通过不同方法间的比较，提出了几种比较适宜氧化锰矿物电化学特性测定的方法，同时对这些不同构造氧化锰矿物电化学性质进行了初步比较。主要结果有： 1、滴定法作为一种测定胶体电荷零点的经典方法，比较适合土壤胶体及针铁矿类PZC较高的氧化物电荷零点的测定，经过延时改进后可适用于锰矿物电荷零点测定，延时盐滴定法测得酸性水钠锰矿、碱性水钠锰矿、锰钾矿、钙锰矿、黑锰矿和针铁矿电荷零点依次为：0.98、4.13、1.72、3.31、5.11和8.41，顺序为：针铁矿＞黑锰矿＞碱性水钠锰矿＞钙锰矿＞锰钾矿＞酸性水钠锰矿； 2、快速电位滴定法虽然忽略pH值缓慢变化的阶段，但反映了氧化物表面性质的变化过程，比较适合氧化锰矿物电荷零点的测定。酸性水钠锰矿、碱性水钠锰矿、锰钾矿、钙锰矿、黑锰矿和针铁矿电荷零点测定值依次为：1.75、3.37、2.10、3.50、4.33和8.00，顺序为：针铁矿＞黑锰矿＞钙锰矿＞碱性水钠锰矿＞锰钾矿＞酸性水钠锰矿； 3、质量滴定法测定的酸性水钠锰矿、碱性水钠锰矿、锰钾矿、钙锰矿、黑锰矿和针铁矿电荷零点测定值依次为：2.25、6.85、3.18、5.92、6.81和7.42，顺序为：针铁矿＞碱性水钠锰矿＞黑锰矿＞钙锰矿＞锰钾矿＞酸性水钠锰矿，即所测氧化锰矿物的电荷零点值普遍偏高，但作为一种新兴方法，目前报道研究甚少，且与其它方法相比更简便、快捷，应具有较大应用前景； 4、在酸性条件下合成的酸性水钠锰矿、锰钾矿采用延时盐滴定法测得的结果均小于快速电位法的测定结果，而在碱性环境中合成的碱性水钠锰矿、黑锰矿、针铁矿则相反；质量滴定法测定供试锰矿物电荷零点均大于延时盐滴定法和快速电位法的测定结果，而针铁矿测定结果相反；华中农业大学硕士学位论文陆泅进20()45、氧化锰矿物的电荷量测定分别采用返滴定法和Mehlich法。反滴定法结果表明:酸性水钠锰矿、碱性水钠锰矿、钙锰矿和锰钾矿的表面负电荷量随pH的升高而增加，其大小顺序为:酸性水钠锰矿>碱性水钠锰矿>锰钾矿>钙锰矿;Mehlich法测定的可变负电荷量(CECv)大小顺序为:酸性水钠锰矿>锰钾矿>钙锰矿>碱性水钠锰矿>黑锰矿，与用返滴定法得到的结果顺序相比，除碱性水钠锰矿偏低外，其它的大体相符，返滴定法和Mehlich法虽然各具优劣，但比较而言，返滴定法因为其准确度高而更适宜锰矿物电荷量测定;6、采用NZ吸附法测得酸性水钠锰矿、碱性水钠锰矿、钙锰矿、锰钾矿和黑锰矿比表面积分别为:75.153、35.035、95.462、130.703和37.954(m飞)，大小顺序为:锰钾矿>钙锰矿>酸性水钠锰矿>碱性水钠锰矿>黑锰矿;结合反滴定法测的电荷量，得到供试氧化锰矿物比表面电荷密度与pH关系曲线，表面电荷密度的大小顺序与表面负电荷量大小顺序有所不同，pH在2一3.5之间时，顺序为:酸性水钠锰矿>碱性水钠锰矿>钙锰矿七锰钾矿，pH在3.5一6之间时，顺序为:碱性水钠锰矿>酸性水钠锰矿>钙锰矿>锰钾矿。更多还原

【Abstract】 The electrochemistry characteristic of Birnessite(-h), Birnessite(-oh), Cryptomelane, Todorokite and Hausmannite were studied by several methods and the results were compared each other.The most suitable methods were put forward. The main resuls were shown as follow:1. As a classical method ,ST method was suitable to determine the PZC of soil and geothite. It was also can determine the PZC of manganese oxide after improved,.The PZC of birnessite(-h), birnessite(-oh), cryptomelane, todorokite , hausmannite and geothite obtained by improved ST method were 0. 98, 4. 13, 1. 72, 3.31, 5.11 and 8. 41, the order was geothite>hausmannite>birnessite(-oh)> todorokite ,cryptomelane , birnessite(-h);2. The slow stage of pH change was ignored for PT method.lt also suited to determine the PZC of manganese oxide. The PZC of birnessite(-h), birnessite(-oh), cryptomelane, Todorokite , hausmannite and geothite obtained by PT method were 1. 75, 3. 37, 2. 10, 3. 50, 4. 33 and 8. 00, the order was geothite>todorokite > birnessite(-oh) > hausmannite > cryptomelane > birnessite(-h);3. The PZC of birnessite(-h), biraessite(-oh), cryptomelane, todorokite , hausmannite and geothite measured by MT method were 2. 25, 6. 85, 3. 18, 5. 92, 6. 81 and 7. 42, the order was geothite>birnessite(-oh) >hausmannite>todorokite >cryptomelane>birnessite(-h).The results of manganese oxide was bigger than that reported in literature ,as contrary, the results of geothite was smaller.As a new method,the reports and researches about it were less . But it was more handy and speediness,and would has great applied outlook.4. The PZC of oxides which synthesized in acidity condition including birnessite(-h), cryptomelane , obtained by improved ST method were less than theresults of those determined by PT method.The oxides synthesized in alkalescence condition , including hausmannite, birnessite(-oh) and geothite ,were on the contrary. The PZC of manganese oxides determined by MT method was greater than the results of those determined by improved ST or PT, geothite were on the contrary.5.The negative charge of manganese oxides were determined by back-titration and Mehlich method respectively.The results of back-titration showed that the amount of negtive charge of manganese oxides was increased with the raising pH,the order was: birnessite(-h) >birnessite(-oh) >cryptomelane >todorokite. The order abtained by Mehlich method was birnessite(-h) >cryptomelane > todorokite >birnessite(-oh)>hausmannite, expect birnessite(-oh).In general,the back-titration method was more suitable to determine the amount of charge of manganese oxides because of its high preciseness.6.The surface area of birnessite(-h) birnessite(-oh), cryptomelane, todorokite and hausmannite measured by N2 adsorption method was 78.183, 38.038, 98.462, 130.703 and 37.954 (m2/g) respectively,the order was cryptomelane> todorokite> birnessite(-h) >birnessite(-oh) ,hausmannite. Combined with the results of back-titration method,the curve of the charge density versus pH was gained.The curve showed that the order was :birnessite(-h) >birnessite(-oh) > todorokite= cryptomelane from pH 2 to 3.5,and birnessite(-oh) >birnessite(-h) >todorokite> cryptomelane from pH 3.5 to 6,which was not according with the order of the amount of negative charge.更多还原