ABSTRACT

Tungsten and cobalt can be recovered from cemented tungsten carbide-Co (WC-Co) scraps using a novel process based on roasting of the scraps with Na₂CO₃ and water leaching of the calcine containing Na₂WO₄. The process was evaluated at different conditions testing several parameters, including Na₂CO₃/WC molar ratio 1:1 – 2:1, roasting temperature in the range 400 – 900ºC, roasting time at 1 – 3h, leaching temperature at ambient – 90ºC and leaching time 1 – 3h. Thermodynamic modelling of the roasting and leaching stages using HSC and Stabcal software allowed an understanding of the speciation of the products at different conditions. Subsequent experiments to determine an optimised conditions of both roasting and water leaching were conducted aiming to yield recoveries of both W and Co in solution over 95%.

Roasting of the scraps with Na₂CO₃ at 800ºC in 3h using Na₂CO₃/WC molar ratio of 1:1 will produce a Na₂WO₄ which can be easily water leached. Over 95% W was recovered after water leaching the calcines at 60ºC in 3h. Over 94% Co was recovered as soluble CoSO₄ using 1M H₂SO₄ with 1.5M H₂SO₃ added as a reductant. The double step of CoCO₃ precipitation using 1.5M Na₂CO₃ and conversion to Co(OH)₂ using 8M NaOH allows a high purity product (>99.5% purity) to be produced with most of the major impurities as Cr and Fe remaining in the residual Na₂CO₃ and NaOH liquors. The levels of these major impurities are 0.05% Cr and 0.3% Fe in the final Co hydroxide product.

摘要

钨和钴可以使用一种新的工艺从硬质合金-Co（WC-Co）废料中回收，该工艺基于用Na ₂ CO ₃焙烧废料和水浸出含Na ₂ WO ₄的煅烧炉。在不同条件下对工艺进行了评估，测试了多个参数，包括Na ₂ CO ₃ / WC摩尔比1：1 – 2：1，焙烧温度在400 –900ºC范围内，焙烧时间为1-3 h，浸出温度为室温– 90ºC，浸出时间1-3小时。使用HSC和Stabcal软件对焙烧和浸出阶段进行热力学建模，可以了解不同条件下产品的形态。为了确定焙烧和水浸的最佳条件，随后进行了实验，目的是使溶液中的W和Co回收率均超过95％。

使用Na ₂ CO ₃ / WC摩尔比为1：1的Na ₂ CO ₃在800ºC下烘烤3小时的废料将产生Na ₂ WO ₄，可以很容易地将其浸出。超过95％的W在水在3于60℃浸出煅后回收ħ。使用1M H ₂ SO ₄和1.5MH ₂ SO ₃作为还原剂，回收了超过94％的Co作为可溶性CoSO ₄。使用1.5M Na ₂ CO ₃进行CoCO ₃沉淀并转化为Co（OH）₂的双步骤使用8M NaOH可以生产出高纯度产品（纯度> 99.5％），并且大部分主要杂质（如Cr和Fe残留在残留的Na ₂ CO ₃和NaOH溶液中）。这些最终杂质在氢氧化钴最终产物中的含量为0.05％铬和0.3％铁。