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Abstract We report the exfoliation process optimization, physicochemical characterizations, and comparative aggregation behavior of the inorganic 2D nanomaterial hexagonal Boron Nitride (h-BN) produced from two repetitive sonication-centrifugation processes with varying centrifugation speeds and recycle frequency: Continuous and Segmented protocols. Enhancing exfoliation efficiency and understanding aqueous stability are essential for sustainable design and environmental applications. Results showed that the Segmented protocol outperformed the Continuous protocol by having a six-fold increase in the exfoliated h-BN nanosheet yield by reusing the unexfoliated bulk h-BN and decreasing centrifugation speeds. Centrifugation speeds of 1880 and 950 rpm produced nanosheets of similar sizes due to the slight difference in the centrifugal force generated in both protocols. Moreover, nanosheets from both protocols had enhanced polarity due to the higher amounts of −OH bonds attached to the exposed edges of the nanosheets. However, the hydroxylation percentage of the nanosheets decreased with centrifugation speed. Both protocols produced h-BN nanosheets that were stable in DI water dispersion. The comparatively lower initial aggregation rate at all centrifugation speeds supported the fact that the Segmented protocol nanosheets were more stable than the Continuous ones. The Segmented protocol h-BN nanosheets showed better overall stability at lower speeds than the other centrifugation speeds. Segmented protocol nanosheets from 3750 rpm had the lowest aggregation rate than the other centrifugation speed. These findings assist in finding the balance between exfoliation protocol, environmental application, and implication of h-BN nanosheets. 

The removal of small molecular weight charged compounds from aqueous solutions using membrane remains a challenge. In this study, polysulfone (PSf)- and sulfonated polyether ether ketone (SPEEK)-based membranes were fabricated via non-solvent induced phase separation process (NIPS) using N-Methyl-2-Pyrrolidone (NMP) as solvent and water as non-solvent. Membranes were characterized structurally and morphologically, followed by toxicity assessment conducted before and after filtration, both with and without annealing at various pH values to evaluate potential leaching of trapped solvent from the membrane pores. Additionally, membrane performance was characterized using binary mixtures of cationic and anionic dyes. The results demonstrated selective filtration behavior, with cationic dyes being preferentially rejected due to size exclusion and electrostatic interactions. Additionally, a key focus of this work was the investigation of solvent leaching, framed within a Safe(r)-by-Design (SbD) approach aimed at enhancing functional performance while minimizing environmental toxicity. Toxicity assessments using a model organism, a nematode Caenorhabditis elegans, revealed that annealing reduced solvent leaching and thus permeate toxicity, particularly at neutral pH values, by facilitating trapped solvent release prior to membrane use. These findings provide insights for the importance of including an SbD approach during membrane casting to fabricate membranes with desirable properties while minimizing toxicity.