温度对酸性草酸-草酸铵溶液浸提土壤无定形铁的影响

以下蜀黄土为试材,研究温度对酸性草酸-草酸铵缓冲溶液浸提土壤无定形铁的影响。结果表明:随着浸提温度的升高,铁的浸提量明显增加。30℃浸提出的铁约为20℃的1.57倍;而50℃浸提出的铁约为20℃的4.43倍。随温度的升高,浸提后土壤残渣的磁化率迅速降低。20℃浸提后残渣的磁化率值比原样略有减少;30℃浸提后残渣的磁化率约为原样的93.6%;50℃浸提后残渣的磁化率只有原样的65.3%。这说明随着温度的升高,以磁性矿物为代表的结晶态铁也被溶解,浸提出的铁其实已不仅是无定形铁。因此,用酸性草酸铵浸提无定形铁时,严格控制20℃的反应温度十分关键。

Influence of Temperature on the Extraction of Amorphous Iron by the Acidic Ammonium Oxalate Method

Xiashu Loess was utilized to study the influence of temperature on the extraction of amorphous iron by acidic ammonium oxalate method.The results showed that the content of extracted iron increased with the increase of temperature.The extracted iron at 30℃ was about 1.57 times of that at 20℃,and the extracted iron at 50℃ was about 4.43 times of that at 20℃.Magnetic susceptibility(χ)of the soil residue after extraction was reduced rapidly with the increase of temperature.χvalues of the residues after extraction at 20℃ were only slightly less than those of the original samples;but those at 30℃ and 50℃ were 93.6% and 65.3%,of the original sample,respectively.It implied that crystal iron such as magnetic minerals in soil samples could be dissolved when the extraction temperature incresed.Hence,as a matter of fact,the iron,extracted at higher temperature is no longer the single form of amorphous iron.Therefore,the extracting temperature should be controlled strictly at 20℃ when determining the content of amorphous iron in soil by this method.