Gandhinagar, 30 September 2026: We generally throw away broken camera lenses, earphones or old phones which have stopped working and cannot be repaired, because they appear useless if they are non-functional. However, these objects harbor rare earth elements (REEs) that have applications in magnets, superconductivity, optics, and batteries, among other things. When such things become part of water, REEs become difficult to recover.
On the other hand, industrial activities can also add toxic metals like lead, cadmium, nickel and manganese to the water. The challenge now is not only how to remove these unwanted, harmful metal pollutants from water, but also to effectively recover the valuable REEs.
What if a single strategy could help solve both issues? In an effort in this direction, researchers from the Indian Institute of Technology Gandhinagar (IITGN), University of Cambridge and University of Birmingham have jointly developed a protocol using a class of ultra-porous materials called metal-organic frameworks (MOFs). They can effectively capture toxic metals from water as well as recover valuable REEs from waste streams. The study, published in Nature Protocols, provides a framework for designing, characterizing and deploying MOFs in water remediation and circular resource applications in real-world situations.
an intelligent filter
Think of MOF as an atomic fishing net. Its numerous pores create a large holding surface, while specially designed chemical sites act like hooks to hold certain metals. Researchers have prepared this trap in such a way that it can catch the required metals on priority. This is like identifying and selecting only red and green colored balls from a box containing hundreds of different colored raw balls.
Some MOFs can have up to 7,000 square meters of internal surface per gram. To put that number into perspective, one gram may look like a tiny speck of powder, but inside it covers a surface area comparable to an entire football field!
pH sensitive
This large internal surface makes MOFs attractive as adsorbents. Simply put, they act as a barrier to substances on their surface. While traditional methods such as precipitation, coagulation and flocculation can be useful for water purification, they are generally sensitive to pH, with best extraction limited to narrow ranges.
Broadly speaking, precipitation allows heavier impurities to settle, coagulation mixes impurities together, and flocculation breaks up small impurity clusters into larger clumps that can be separated.
These methods also require large infrastructure facilities and produce large amounts of sludge, a type of sludge-like waste that must be handled and disposed of. Other processes, such as electrochemical treatment, have higher economic and environmental costs.
Adsorption provides an effective alternative that is simple to operate, has wide applicability, and remains effective even at low concentrations of contaminants. In this method, the focus is on the degree of affinity of the target metals towards a specially prepared surface. Therefore, it has the ability to remove up to 90–99% of contaminants like a highly selective filter! By using adsorption based methods, the generation of secondary contaminants can be avoided and the material can be reactivated and reused for reuse. In this field, MOFs are of particular importance due to their extraordinary design flexibility for capturing and recovering metals.
From the laboratory to the real world
Industrial liquid effluents, which are waste products discharged into water bodies from manufacturing, mining and chemical process facilities, contain not only single but many metals, as well as other pollutants such as pesticides, detergents and organic pollutants. The protocol describes a method that can be used to use MOFs as adsorbent for the recovery and removal of metals under controlled conditions.
The protocol involves testing in complex real-world scenarios. For example, removal and recovery were evaluated using wastewater that was alkaline (pH ~ 8.5), turbid, and high in dissolved solid impurities. This method was also tested in samples obtained from artificial sea water and e-waste. The workflow developed in this study can be applied to similar adsorbents and other pollutants.
“For me, the most interesting aspect was that the MOF in our protocol showed significant adsorption capabilities,” said Dhruv Menon (BTech, IITGN). He added, “Experiments show that one gram of copper-based MOF can hold about half a gram of lead (490 mg/g), and about five grams of cadmium (264 mg/g) and manganese (226 mg/g). For rare-earth elements, that's about a third of a gram per gram of material (351 mg/g neodymium, 343 mg/g It can hold yttrium, 335 mg/g dysprosium, 337 mg/g terbium and 345 mg/g europium). Mr. Menon is currently a doctoral student in the Department of Chemical Engineering and Biotechnology at the University of Cambridge.
towards sustainability
Prof. As explained by Suparb Mishra, “There is a need for approaches that can address multiple environmental challenges simultaneously. Our focus was on engineering the performance of MOFs for use in environmental remediation applications. However, it is important to understand that controlled batch experiments cannot fully predict behavior in complex wastewaters. Factors such as large-scale fabrication, cost analysis, MOF life-cycle assessment, and regulatory testing need to be considered,” Dr. Mishra is Jignaben Patel Chair Professor in the Department of Materials Engineering at IITGN and Principal Investigator of the Bio Nano Materials Group.
Other team members involved in this study include Prathamesh Bhadane (PhD, IITGN; Postdoctoral Fellow, IIT Bombay), Priya Mahato (Doctoral Student, IITGN), Pratik Goyal (PhD, IITGN), Dr. Isolt Lynch (Professor, School of Geography, Earth and Environmental Sciences, University of Birmingham), and Dr. Swaroop Chakraborty (NERC Fellow, University of Birmingham).
This research is in line with the Critical Mineral Recycling Incentive Scheme of the Government of India, part of the National Critical Mineral Mission, to develop local recycling capacity to separate and produce critical minerals from secondary sources, including increasing volumes of e-waste and battery waste. IIT Gandhinagar is a partner in the Center of Excellence on National Critical Minerals Mission hosted at IIT (ISM) Dhanbad. These findings are also consistent with the UK-India Technology Security Initiative, which involves collaboration on the sustainable extraction and recovery of critical minerals from waste streams. They also align with the United Nations Sustainable Development Goals (SDGs) 6, 9 and 12, which focus on clean water and sanitation, industry and innovation, and responsible consumption and production.