Reclamation of boron from solid and liquid streams for fertilizer application

Boron (B) is a crucial element for efficient plant growth and development; therefore, B-based fertilisers have been employed in agricultural applications. The need for B-based fertilisers for agricultural uses is continuously increasing as a result of the world's growing population. It is expected that the global market for B-based fertiliser will grow by around $6.3 billion by 2032; hence, demand for B sources will also increase. In addition to being used in fertiliser, B is also employed in the production of neodymium iron B (NdFeB) permanent magnets. The demand for NdFeB magnets is also continuously increasing. Hence, it is of the utmost importance to reclaim B from secondary resources due to the rising demand for B in a wide variety of applications. This review study addresses the recovery of B from various waste streams. The main focus is on the recovery of B from spent NdFeB magnets, borax sludge, and liquid streams such as brine water, seawater, sewage, industrial wastewater, and agricultural effluents. Different technologies for B recovery are discussed, such as sorption, solvent extraction, membrane processes, precipitation, and hydrometallurgical methods. Solvent extraction has been found to be a very effective approach for reclaiming B from spent NdFeB magnet waste and from liquid streams with high B concentration (>1-2 g/L). Further, the application of B-based fertiliser in agriculture application is reviewed. Challenges associated with B recovery from waste streams and future perspectives are also highlighted in this review.