Current research has widely applied heteroatom doping
for the promotion
of catalyst activity in peroxymonosulfate (PMS) systems; however,
the relationship between heteroatom doping and stimulated activation
mechanism transformation is not fully understood. Herein, we introduce
nitrogen and sulfur doping into a Co@rGO material for PMS activation
to degrade tetracycline (TC) and systematically investigate how heteroatom
doping transformed the activation mechanism of the original Co@rGO/PMS
system. N was homogeneously inserted into the reduced graphene oxide
(rGO) matrix of Co@rGO, inducing a significant increase in the degradation
efficiency without affecting the activation mechanism transformation.
Additionally, S doping converted Co3O4 to Co4S3 in Co@rGO and transformed the cooperative oxidation
pathway into a single non-radical pathway with stronger intensity,
which led to a higher stability against environmental interferences.
Notably, based on density functional theory (DFT) calculations, we
demonstrated that Co4S3 had a higher energy
barrier for PMS adsorption and cleavage than Co3O4, and therefore, the radical pathway was not easily stimulated by
Co4S3. Overall, this study not only illustrated
the improvement due to the heteroatom doping of Co@rGO for TC degradation
in a PMS system but also bridged the knowledge gap between the catalyst
structure and degradation performance through activation mechanism
transformation drawn from theoretical and experimental analyses.
Nanofiltration (NF) is a promising post-treatment technology for providing high-quality drinking water. However, membrane fouling remains a challenge to long-term NF in providing high-quality drinking water. Herein, we found that coupling pre-treatments (sand filtration (SF) and ozone–biological activated carbon (O3-BAC)) and NF is a potent tactic against membrane fouling while achieving high-quality drinking water. The pilot results showed that using SF+O3-BAC pre-treated water as the feed water resulted in a lower but a slowly rising transmembrane pressure (TMP) in NF post-treatment, whereas an opposite observation was found when using SF pre-treated water as the feed water. High-performance size-exclusion chromatography (HPSEC) and three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectroscopy determined that the O3-BAC process changed the characteristic of dissolved organic matter (DOM), probably by removing the DOM of lower apparent molecular weight (LMW) and decreasing the biodegradability of water. Moreover, amino acids and tyrosine-like substances which were significantly related to medium and small molecule organics were found as the key foulants to membrane fouling. In addition, the accumulation of powdered activated carbon in O3-BAC pre-treated water on the membrane surface could be the key reason protecting the NF membrane from fouling.
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.