酸解钢渣制备多元掺杂磷酸铁及其成分控制

Preparation and Composition Control of Multi-metal-doped Iron Phosphate by Acidolysis of Steel Slag

以钢渣酸解滤液和磷酸的复杂体系为研究对象,通过pH值控制,考察了体系中Fe,Mn,Cr,Al,Mg,Ti等多种目标离子在PO4^3-环境下的共沉淀行为,选择性回收钢渣中多种目标金属并制备多元掺杂磷酸铁.结果表明,沉淀产物为无定型非晶前驱体,pH=3.0-4.0时,前驱体中金属总摩尔数与磷摩尔数比接近1,且掺杂元素总量适中,粒径约50nm,700℃焙烧可得粒径200-400nm的单相六方晶系多元掺杂磷酸铁;继续增大pH值则非Fe金属含量过多,产物出现杂相.

Dissolving steel slag in sulfuric acid and reacting the filtrate with phosphoric acid through adjusting pH value, a multi-metal-doped iron phosphate is prepared by recovery of multiple metals from steel slag. The precipitation behaviors of target metal ions, such as Fe, Mn, Cr, Al, Mg and Ti, existing in the reaction system with appearance of PO4^3-polyanion are discussed. The results indicate that the precursors precipitated at pH=3.0-4.0 exhibit amorphous particles of about 50 nm, with molar ratio of total metals to phosphorous nearly to 1. Roasted at 700℃ for 5 h in air, the precursors crystallize into homogeneous powder of about 200 nm, and are identified by XRD as single-phase multi-doped iron phosphate with a hexagonal structure. Further increase of pH value to 5.0 and 6.0 causes an excessive precipitation of nonferrous metal elements in the product, leading to a departure from stoichiometric ratio and presence of undesirable phases. The inexpensive metals-doped iron phosphate precursor for synthesis of lithium iron phosphate can be prepared from the steel slag.