Successive alkalinity producing systems (SAPSs) are widely used for treating acid mine drainage (AMD) and alleviating clogging commonly occurring in limestone systems due to an amorphous ferric precipitate. In this study, iron dust, bone char, micrite and their admixtures were used to treat arsenic-containing AMD. A particular interest was devoted to arsenic removal performance, mineralogical constraints on arsenic retention ability and permeability variation during column experiment for 140 days. The results showed that the sequence of the arsenic removal capacity was as follows: bone char > micrite > iron dust. The combination of 20% v/v iron dust and 80% v/v bone char/micrite columns can achieve better hydraulic conductivity and phosphorus-retention capacity than single micrite and bone char columns. The addition of iron dust created reductive environment and resulted in the transformation of coating material from colloidal phase to secondary mineral phase, such as green rust and phosphoerrite, which obviously ameliorates hydraulic conductivity of systems. The sequential extraction experiments indicated that the stable fractions of arsenic in columns were enhanced with help of iron dust compared to single bone char and micrite columns. A combination of iron dust and micrite/bone char represented a potential SAPS for treating As-containing AMD.
Herein, Co 3 O 4 nanopolyhedrons with multi-mimics of peroxidase (POD)-, oxidase (OXD)-, catalase (CAT)-, and glutathione peroxidase (GPx)-like activities were developed and utilized in the application of regulating the level of cellular oxygen and hydrogen peroxide combined with polydopamine (PDA). It was found that the multi-mimic activities can be controlled by pH and the OXD-and POD-like activities were the best when the pH was 4 but became weak under weakly acidic or neutral conditions. Meanwhile, the CAT-like activity was the best under neutral and weakly acidic conditions, and the GPx-like activity was better in neutral conditions than in acidic conditions. According to the high CAT-like activity of Co 3 O 4 nanopolyhedrons under weakly acidic conditions, especially at the tumor cell microenvironment, the Co 3 O 4 nanopolyhedrons can catalytically transform the H 2 O 2 into O 2 without interferences from other mimic activities. After coating with PDA, the Co 3 O 4 @PDA with good biocompatibility and dispersion can also be catalyzed to produce O 2 in the cellular microenvironment with high efficiency. The corresponding H 2 O 2 and O 2 fluorescent probes were used to monitor the process, and the main mechanisms were investigated through fluorescence spectra and confocal fluorescence microscopy. This work not only verifies the multi-enzyme properties of Co 3 O 4 nanopolyhedrons but also provides a nanomaterial for the regulation of the content of H 2 O 2 or O 2 in cells by utilizing the CAT-like enzyme property of the nanomaterial. It is considered that the concentration variation of the active small molecules in the cell microenvironment regulated by nanoenzymes may provide some basis for cancer diagnosis and treatment. KEYWORDS: multi-mimetic enzyme properties, Co 3 O 4 nanopolyhedrons, CAT-like activity, content regulation of O 2 , fluorescent probe
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.