Copper MOF from an IIT Gandhinagar-led team captures both lead and rare earths in batch tests

Lead was the highest loading reported. The same framework took up "roughly a quarter of a gram each of cadmium (264 mg/g) and manganese (226 mg/g)," said Dhruv Menon, an IITGN graduate who is now a doctoral student in chemical engineering at Cambridge ^[3][5]. Turned around, the loadings say how much adsorbent a plant would have to handle. At 490 mg per gram, a kilogram of lead ties up about 2 kg of framework per loading cycle. A kilogram of neodymium, at 351 mg per gram, ties up about 2.85 kg ^[15][16].

Two figures repeated in both reports describe MOFs and adsorption generally. The 7,000 square meters per gram of internal surface is what some MOFs reach ^[8]. The 90% to 99% removal figure is phys.org's description of what adsorption has the potential to achieve ^[12]. The measured results for the copper framework are the loadings Menon gave.

Capturing both groups of metals makes recovery harder. The researchers say they tuned the framework to preferentially trap the metals they are after ^[9]. By mass, though, it holds about 1.4 times as much lead as neodymium ^[19], and the five rare earths load within 16 mg/g of one another, under 5% of their 342 mg/g average ^[17][18]. I'd expect a framework with that profile, fed a mixed effluent, to carry toxic and valuable metals together, with the rare earths then stripped off and sorted in a later step. The reports do not say whether the loadings came from single-metal solutions or from the real-world samples, how rare earths are released apart from lead, or how many regeneration cycles the framework survives. Phys.org's account says adsorbents of this kind can be regenerated and reused ^[14].

Superb Misra, the IITGN materials engineering professor who is the group's principal investigator, described the motivation broadly. "There is a need for approaches that can solve multiple environmental challenges simultaneously," he said ^[11][13]. He was specific about the limits too. Misra said "it is crucial to understand that controlled batch experiments cannot fully predict behaviours in complex wastewater," and added: "There is a need to look at factors like large-scale fabrication, cost analyses, MOF life-cycle assessment and regulatory testing" ^[10].

In my view the evidence supports a narrower claim than cleanup that pays for itself. In batch, one copper framework holds hundreds of milligrams per gram of both toxic metals and rare earths ^[3][4]. Capacity per gram is a laboratory figure. Whether recovered rare earths cover the cost of making and cycling the framework depends on the cost analyses and large-scale fabrication work Misra lists as still needed ^[10].