Abstract Spent fluid cracking catalyst (FCC) is an abundant waste material derived from oil refining processes and notably characterized by its content in rare earth metals, such as cerium (Ce) and lanthanum (La). In this work, it was our main aim to develop a simple but effective flowsheet, based on a single acid assisted leaching step followed by two consecutive precipitation steps, for recovering La with high purity from the FCCs. Firstly, three (conventional, ultrasound- and microwave-assisted) leaching strategies were tested using two acids (sulphuric acid, H2SO4, and hydrochloric acid, HCl). Microwave-assisted leaching was revealed to be the most efficient [(99.4 ± 0.9)% of La] and fastest leached (1 cycle of 90 s) strategy using a lower concentration of acid (1 M HCl) and low liquid-solid ratio (L/S = 5). Subsequently, a sequential selective alkaline and oxalate precipitation was capable of producing an aluminium hydroxide with 88.7% of purity by increasing the pH up to 6 and a highly pure (99.7%) salt of lanthanum oxalate (which can be calcinated into a reusable lanthanum oxide) using a reduced oxalate concentration. The proposed process is independent of the initial Al concentration present in the hydrochloric acid FCCs leachates and widely applicable (for [La] > 0.04 M, complete La precipitation can be achieved regardless of its initial concentration using a molar [oxalate]/[La] ratio of 2). Moreover, it is significantly simpler and faster than existing methods and minimizes the consumption of energy and reagents to a bare minimum, with accompanying cost reduction and environmental benefits.

中文翻译：

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一种使用环保策略从流化裂化催化剂中回收 La（和 Al）的简单、高效和选择性工艺

摘要 废流化裂化催化剂（FCC）是炼油过程中产生的一种丰富的废料，其显着特点是含有铈（Ce）和镧（La）等稀土金属。在这项工作中，我们的主要目标是开发一个简单但有效的流程，基于单个酸辅助浸出步骤，然后是两个连续的沉淀步骤，用于从 FCC 中回收高纯度的 La。首先，使用两种酸（硫酸 H2SO4 和盐酸 HCl）测试了三种（常规、超声波和微波辅助）浸出策略。微波辅助浸出被证明是最有效的 [(99.4 ± 0.9)% La] 和最快的浸出（1 个 90 秒循环）策略，使用较低浓度的酸（1 M HCl）和低液固比（ L/S = 5)。随后，通过将 pH 值提高到 6，连续选择性碱性和草酸盐沉淀能够产生纯度为 88.7% 的氢氧化铝和草酸镧的高纯度 (99.7%) 盐（可煅烧成可重复使用的氧化镧），使用草酸盐浓度降低。所提出的过程与盐酸 FCC 浸出液中存在的初始 Al 浓度无关，并且具有广泛的适用性（对于 [La] > 0.04 M，无论初始浓度如何，使用摩尔 [草酸盐]/[La] 都可以实现完全的 La 沉淀） 2）的比例。此外，它比现有方法更简单、更快速，并将能源和试剂的消耗降至最低，同时降低成本并带来环境效益。