Parallel factor (PARAFAC) analysis enables a quantitative analysis of excitation-emission matrix (EEM). The impact of a spectral variability stemmed from a diverse dataset on the representativeness of the PARAFAC model needs to be examined. In this study, samples from a river, effluent of a wastewater treatment plant, and algae secretion were collected and subjected to PARAFAC analysis. PARAFAC models of global dataset and individual datasets were compared. It was found that the peak shift derived from source diversity undermined the accuracy of the global model. The results imply that building a universal PARAFAC model that can be widely available for fitting new EEMs would be quite difficult, but fitting EEMs to existing PARAFAC model that belong to a similar environment would be more realistic. The accuracy of online monitoring strategy that monitors the fluorescence intensities at the peaks of PARAFAC components was examined by correlating the EEM data with the maximum fluorescence (Fmax) modeled by PARAFAC. For the individual datasets, remarkable correlations were obtained around the peak positions. However, an analysis of cocktail datasets implies that the involvement of foreign components that are spectrally similar to local components would undermine the online monitoring strategy.
Nanofiltration (NF) membranes have been widely applied
in many
important environmental applications, including water softening, surface/groundwater
purification, wastewater treatment, and water reuse. In recent years,
a new class of piperazine (PIP)-based NF membranes featuring a crumpled
polyamide layer has received considerable attention because of their
great potential for achieving dramatic improvements in membrane separation
performance. Since the report of novel crumpled Turing structures
that exhibited an order of magnitude enhancement in water permeance
(Science2018360518521), the number of published research
papers on this emerging topic has grown exponentially to approximately
200. In this critical review, we provide a systematic framework to
classify the crumpled NF morphologies. The fundamental mechanisms
and fabrication methods involved in the formation of these crumpled
morphologies are summarized. We then discuss the transport of water
and solutes in crumpled NF membranes and how these transport phenomena
could simultaneously improve membrane water permeance, selectivity,
and antifouling performance. The environmental applications of these
emerging NF membranes are highlighted, and future research opportunities/needs
are identified. The fundamental insights in this review provide critical
guidance on the further development of high-performance NF membranes
tailored for a wide range of environmental applications.
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