The backgrinding of silicon (Si) wafers has resulted in a loss of ∼70% of valuable Si materials. Consequently, an effluent known as diluted backgrinding wastewater (DBGW) is generated, containing nanosized silicon/silica colloids. Here, we discussed the challenges associated with the effective separation of Si-based waste from the DBGW based upon two perspectives, namely, a nanosized effect and a colloidal stability effect. Then, we revealed the limitation with the currently used coagulation-flocculation approach, which introduces impurities into the highly pure Si. Membrane-based filtration techniques have been adopted, but the serious fouling problem associated with colloidal Si/SiO2 renders them almost impractical. Apart from that, the potential use of highly pure Si waste generated in the semiconductor industry in lithium ion batteries (LIBs) has been discussed. This Perspective aims to provide insights into the challenges associated with the Si recovery from DBGW and suggests its potential use in LIBs.
Urbanization requires the conversion of natural land cover to cover with human-constructed elements and is considered a major threat to biodiversity. Bee populations, globally, are under threat; however, the effect of rapid urban expansion in Southeast Asia on bee diversity has not been investigated. Given the pressing issues of bee conservation and urbanization in Southeast Asia, coupled with complex factors surrounding human-bee coexistence, we investigated bee diversity and human perceptions of bees in four megacities. We sampled bees and conducted questionnaires at three different site types in each megacity: a botanical garden, central business district, and peripheral suburban areas. Overall, the mean species richness and abundance of bees were significantly higher in peripheral suburban areas than central business districts; however, there were no significant differences in the mean species richness and abundance between botanical gardens and peripheral suburban areas or botanical gardens and central business districts. Urban residents were unlikely to have seen bees but agreed that bees have a right to exist in their natural environment. Residents who did notice and interact with bees, even though being stung, were more likely to have positive opinions towards the presence of bees in cities.