Dichloromethane-Assisted Phase Separation for Simultaneous Recovery of Oil and Rare Earth Elements from Oil-Rich Grinding Sludge
DOI:
https://doi.org/10.17159/Abstract
Grinding sludge is a gel-like hazardous waste generated in large quantities during metal cutting processes. Conventional calcination and hydrometallurgical treatment of oil-rich grinding sludge emit flue gases and generate insoluble residues. This study proposes dichloromethane-assisted phase separation under mild conditions to enhance oil removal and metal recovery by overcoming encapsulation effects. NdFeB grinding sludge, containing 10.4% oil, 8.3% Nd, 4.5% Pr, and 55.8% Fe, was selected as a representative material. The dissolution efficiency of the sludge in hydrochloric acid alone or after dichloromethane pretreatment was less than 85%, whereas complete dissolution was achieved using a dichloromethane/hydrochloric acid mixed solvent. After that, phase separation produced an organic phase enriched with 10.44% oil, as well as carbon and grease, and an aqueous phase containing 10 g/L Nd, 3.75 g/L Pr, and 71 g/L Fe. The organic phase could be easily evaporated, allowing for the recovery of approximately 90% of the dichloromethane, with oil, carbon powder, and grease remaining as residues. The aqueous phase was subsequently processed to sequentially precipitate a double salt containing 98.58% Nd/Pr and an iron yellow product with 99.97% Fe. This approach provides an effective and economical strategy for the simultaneous recovery of oil and metallic products from grinding sludge, avoiding the need for harsh conditions or costly equipment. Consequently, it offers significant potential for practical on-site applications in industrial settings.
Downloads
Published
Issue
Section
License
Copyright (c) 2026 Minglin Zheng, lan Xin, weilu Yang, Kaung Htet Oo, yu Chen, wensheng Qin, dejun Bian, hua Kang, suiyi Zhu
This work is licensed under a Creative Commons Attribution 4.0 International License.
THE INSTITUTE, AS A BODY, IS NOT RESPONSIBLE FOR THE STATEMENTS AND OPINIONS ADVANCED IN ANY OF ITS PUBLICATIONS.
Copyright© 1978 by The Southern African Institute of Mining and Metallurgy. All rights reserved. Multiple copying of the contents of this publication or parts thereof without permission is in breach of copyright, but permission is hereby given for the copying of titles and abstracts of papers and names of authors. Permission to copy illustrations and short extracts from the text of individual contributions is usually given upon written application to the Institute, provided that the source (and where appropriate, the copyright) is acknowledged. Apart from any fair dealing for the purposes of review or criticism under The Copyright Act no. 98, 1978, Section 12, of the Republic of South Africa, a single copy of an article may be supplied by a library for the purposes of research or private study. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means without the prior permission of the publishers. Multiple copying of the contents of the publication without permission is always illegal.
U.S. Copyright Law applicable to users In the U.S.A.
The appearance of the statement of copyright at the bottom of the first page of an article appearing in this journal indicates that the copyright holder consents to the making of copies of the article for personal or internal use. This consent is given on condition that the copier pays the stated fee for each copy of a paper beyond that permitted by Section 107 or 108 of the U.S. Copyright Law. The fee is to be paid through the Copyright Clearance Center, Inc., Operations Center, P.O. Box 765, Schenectady, New York 12301, U.S.A. This consent does not extend to other kinds of copying, such as copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale.
