Oxidative acid leaching behavior of Fe–Ni–Co alloy powder derived from a laterite ore

Abstract

The demand for Ni and Co has surged due to the rapid expansion of the electric vehicle industry. Thus, developing efficient and eco-friendly metallurgical routes for extracting these metals has become imperative. This study introduces a sustainable and effective method for extracting Ni and Co from Ni–Co–Fe alloy powder obtained from limonitic laterite ores through selective reduction and magnetic separation. The leaching efficiency for Ni, Co, and Fe was 89.4%, 94.8%, and 96.5%, respectively, under the following conditions for leaching: 3 mol/L H2SO4, 85°C, 10 mL/g liquid–solid ratio, and 90 min leaching time. The incorporation of H2O2 enhanced the leaching efficiency for Ni, Co, and Fe. The redox potential of the solution plays a crucial role in acid dissolution, and H2O2 enhances Ni and Co dissolution. Phosphate precipitation facilitated the removal of Fe from the leachate, affording a 96.1% Fe removal ratio and 2.29% Ni loss.

1. Introduction

Nickel is a crucial transition metal primarily utilized in the production of stainless steel, alloys, and new-energy vehicle (NEV) power batteries [1–2]. Historically, the demand from the stainless steel industry has significantly influenced nickel consumption trends [3]. However, the advent of the NEV industry has led to the widespread use of nickel-rich cathode materials in power batteries [4–5]. This shift has altered the nickel consumption pattern from being predominantly driven by the stainless steel sector to a dual dominance of stainless steel and battery sectors [6–7]. Land-based nickel deposits are predominantly categorized as nickel laterite and nickel sulfide [8–9], and over 70% of nickel is found in laterite ores [10]. Nickel sulfide ores were previously preferred for their suitability for beneficiation, which reduces smelting costs [11]. However, as nickel sulfide ore reserves are depleting because of ongoing exploitation, attention is shifting toward nickel laterite ores [12]. To date, nickel from laterite ores accounts for approximately 70% of the global nickel production [13].

Nickeliferous laterite ores are typically classified as saprolite type (high nickel and low iron contents) or limonite type (high iron and low nickel content) [14]. Saprolitic ores are commonly utilized in pyrometallurgical smelting to produce ferronickel, which is often further refined into stainless steel. By contrast, limonitic ores are predominantly processed through hydrometallurgical routes to yield intermediate nickel and cobalt products, which are often refined into sulfate salts. The production of these sulfates is heavily dependent on the processing of mixed hydroxide precipitate (MHP) or mixed sulfide precipitate, which are both derived through the high-pressure acid leaching (HPAL) of limonitic ores [15]. The growing demand for nickel sulfate, driven by the expanding NEV industry, has highlighted limitations in current HPAL methods, including high capital investments and constrained capacities [16]. To bridge the nickel sulfate supply gap, a proposed solution involves converting ferronickel, which is the product of the pyrometallurgical processing of saprolitic ores, into nickel matte, which can then be processed into nickel sulfate [17]. However, this process is energy intensive and presents potential environmental risks.