Freeze-drying cuts cost and energy for lead-capturing water treatment material

Scientists at the University of Birmingham have demonstrated that freeze-drying a copper-imidazolate metal-organic framework (MOF) called BNMG-1 increases isolated yield more than threefold and cuts estimated electricity demand per gram by about 74% compared with conventional processing. The work, published in Green Chemistry, lowers the estimated lab-scale production cost from roughly $19 per gram to just over $5 per gram.

MOFs are porous materials with metal nodes linked by organic molecules, giving them large internal surface areas that can selectively capture heavy metals from water. However, many MOF manufacturing routes are solvent- or energy-intensive, and the metals in some frameworks can leach into treated water, causing secondary contamination. These issues have kept most MOFs at pilot or demonstration stages.

The Birmingham team, led by NERC Independent Research Fellow Dr. Swaroop Chakraborty, previously developed a water-based synthesis for BNMG-1 that produces pellets rather than fine powder, making the material easier to handle in real-world settings. The MOF was engineered to recover rare earth elements and heavy metals from industrial waste streams and has shown low copper leaching in tests with real water samples.

In the new study, the freeze-dried BNMG-1 removed more than 90% of lead from solution within the first hour and maintained high removal across four consecutive treatment batches. The material retained its principal structural features after seven days of exposure to air, freshwater-like conditions, and artificial seawater.

The researchers say redesigning this single processing step addresses both manufacturing efficiency and environmental performance. University of Birmingham Enterprise has filed a patent application on the method and the material, and the team is seeking industrial partners in mining, electronic waste, or water treatment for licensing or pilot-scale trials.