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化学共沉淀工艺制备Fe_3O_4的磁性与沉淀剂、混合方式、溶液浓度、Fe~(++)与Fe~(+++)、Fe~(++)与OH~(-1)离子的克分子比率等密切相关.当碱性溶液缓慢滴入Fe~(++),Fe~(+++)混合溶液中时,Fe_3O_4的生成过程大致上分为两个阶段:a)所有的(Fe~(++),Fe~(+++),OH~(-1),Cl~-)离子将以非晶态的中间沉淀物沉淀出来,直到溶液中所有的Fe~(++),Fe~(+++)离子均被沉淀净为止.b)第一阶段结束后,当继续加入碱性溶液时,上述的中间沉淀物按下式反应而转变为Fe_3O_4.非晶→Fe_3O_4·4H_2O→Fe_3O_4·2H_2O(绿锈Ⅰ)→Fe_3O_4·4/3H_2O(绿锈Ⅱ)→Fe_3O_4直到中间沉淀物完全转变为Fe_3O_4为止.Fe_3O_4的生成过程用Fe(OH)_2+2Fe(OH)_3→Fe_3O_4+4H_2O反应式表述不甚妥当,应表述为下式较为合理.Fe~(++)+2Fe~(+++)+8OH~(-1)→Fe_3O_4+4H_2O
Chemical coprecipitation preparation of Fe 3 O 4 magnetic and precipitant, mixing mode, solution concentration, Fe ~ (++) and Fe ~ (+++), Fe ~ (++) and OH ~ (-1) Ratio, etc. When the alkaline solution is slowly dropped into the mixed solution of Fe ~ (++) and Fe ~ (+++), the formation process of Fe 3 O 4 is roughly divided into two stages: a) (++), Fe ~ (+++), OH ~ (-1) and Cl ~ - ions will precipitate out as amorphous intermediate precipitates until all Fe ~ (++), Fe ~ (+++) ions are precipitated net so far b) after the end of the first phase, when continuing to add alkaline solution, the intermediate precipitate according to the following reaction and transformed into Fe_3O_4 amorphous → Fe_3O_4 · 4H_2O → Fe_3O_4 · 2H_2O (green rust Ⅰ) → Fe_3O_4 · 4 / 3H_2O (green rust Ⅱ) → Fe_3O_4 until the intermediate precipitates completely changed to Fe_3O_4.The formation process of Fe_3O_4 was characterized by Fe (OH) 2 + 2Fe (OH) 3 → Fe_3O_4 + 4H_2O reaction formula is not appropriate, should be described as the following formula is more reasonable.Fe ~ (++) +2 Fe ~ (+++) +8 OH ~ (-1) → Fe_3O_4 + 4H_2O