US 2019/0002309 Al  31  Jan. 3, 2019  [0310]  As a robust, high-sorption capacity material, the  optimized nanocarbon sorbent fabricated herein via electro› spinning represents a significant practical advance in POU  drinking water treatment. Relying on integrated CNTs for  improved strength and sorption capacity, and macroporosity  for flexibility and external surface area, the optimized CNF - CNT composite (CNT2-PTA2.4) exhibited capacities com› parable to and sorption kinetics much faster than those of  commercial GAC. The promise of these materials is their  ability to be deployed in high-flux systems while minimizing  application footprint. Depending on solution complexity and  the number of dissolved targets, relatively low masses can  be used to treat large volumes under dynamic flow condi› tions (e.g., 14 mg for 2 L of treatment for SMX, or 7 mg/L).  [0306]  Collectively, therefore, mixture treatment results  support CNF-CNT composites targeting organic micropoll› utants via multiple sorption mechanisms (e.g., hydrophobic  interactions and/or specific binding interactions), presum› ably occurring at different sites on the sorbent surface. This  is consistent with our earlier findings with ATZ and SMZ,  which on occasion exhibited comparable uptake on CNF› CNT composites despite their differences in polarity (i.e.,  sorption was not easily predictable from log K$_{0}$ w values).  This is also consistent with prevailing wisdoms in the  carbon-based sorbent literature, particularly at trace (sub› ppm) concentrations, where the presence of acid/base  groups and/or hydrogen bond donors/acceptors have been  [0305]  Essentially unretained by the CNF-CNT composite  were metoprolol and cotinine. For metoprolol (pK$_{0 }$ 9.09), its  poor removal is in part due to its pH-dependent uptake, as  we observed its extent of sorption to decrease at lower pH  values where it is positively charged (FIG.  34).  Cotinine,  which is relatively polar (log K$_{0}$ w 0.07) and neutrally  charged (pK$_{0 }$ 4.36) in our test system, also was unretained  by the CNF-CNT sorbent. Thus, despite containing hetero› cyclic N sites typically prone to specific binding interac› tions, the polarity of cotinine appears sufficient to inhibit its  binding to the CNF-CNT surface.  [0309]  Despite the shorter breakthrough times, micropo› llutant removal in the carbonate-containing system could  generally be divided into two categories. Compounds well› removed in more idealized, deionized water systems (FIG.  32B;  i.e., SDMX, naproxen, bezafibrate, and gemfibrozil)  broke through at -2-fold greater volume than the remaining  compounds. Notably, metoprolol was removed slightly bet› ter in carbonate buffered systems, behavior that can be  ascribed to its pH-dependent uptake (see FIG.  34).  Thus,  while the same sorption processes appear to be at play in this  more representative aquatic matrix, composite ability (pre› sumably both uptake rate and capacity) is, not surprisingly,  influenced by the presence of co-solutes. Accordingly, these  filters are likely best applied as a final polishing step for  water treatment (e.g., point of use application at the tap)  after effective management to limit competitive co-solutes.  [0308]  Finally, these trends in micropollutant sorption  were also observed in systems with 1 mM carbonate (100  mg/L as CaCO$_{3 }$ or moderate hardness), although break› through occurred much more rapidly (FIG.  33).  This behav› ior likely indicates sorption inhibition by dissolved carbon› ate species (i.e., bicarbonate; HCO$_{3 }$ -).  A competitive or  inhibitory role for bicarbonate is supported by results from  batch experiments, where increasing bicarbonate concentra› tion decreased the extent of ATZ and SMX sorption (FIG.  36).  From the inhibition observed from bicarbonate as a  co-solute, application may require integration of another  filter layer designed to specifically remove interfering spe› cies via other mechanisms (e.g., ion exchange).  [0304]  Modest removal (breakthrough after 2 Lor 460,000  bed volumes) was observed for caffeine (log K$_{0}$ w -0.07),  acetaminophen (log K$_{0}$ w 0.46), and ATZ (log K$_{0}$ w 2.61),  despite their wide range of polarities. As with sulfa drugs,  caffeine and atrazine contain heterocyclic nitrogen moieties,  and we hypothesize that specific interactions between these  electron-rich N-containing rings and sites on the CNF-CNT  composite surface enhance the sorption affinity for these  compounds. This behavior is consistent with previous obser› vations of a lack of correlation between log K$_{0}$ w and removal  trends on activated carbon for compounds containing het› erocyclic/aromatic nitrogen groups. Removal of acetamino› phen, which has a secondary amine group but is neutrally  charged in our test solution (pK$_{0 }$ 9.48), has also previously  been proposed to be higher on activated carbon than would  be predicted by log  Kaw•  [0303]  In the simplified aquatic matrix, >95% removal  was maintained after 3 L (-690,000 bed volumes) of opera› tion for naproxen, bezafibrate, and gemfibrozil. This behav› ior is particularly noteworthy given prior reports of poor  removal of naproxen and gemfibrozil by activated carbons.  These represent the three compounds with the largest  reported log K$_{0}$ w values (log K$_{0}$ w>3.1), but all three also  have deprotonated -OH groups under the conditions of our  flow through experiments (pK$_{0 }$ 4.50, 3.73, and 4.48, for  naproxen, bezafibrate and gemfibrozil, respectively). We  propose the primary driver for their sorption is via hydro› phobic interactions with the sorbent surface, driven by the  non-polar moieties (e.g., aromatic rings) in their structures.  When examining performance toward less hydrophobic  compounds (based on reported log K$_{0}$ w values), the highest  degree of removal was observed for the sulfa drugs (sul› fadimethoxine (SDMX) and SMX), with >90% removal  observed throughout for SDMX (log K$_{0}$ w =4.63) and com› plete breakthrough of SMX only after 3 L of effluent  volume. The relatively good removal of these sulfa drugs  likely is attributable in part to the lower pH (-5 .5) of these  trials, with pH edge data (see FIG.  30C)  revealing improved  sorption for sulfa drugs at lower pH (pK$_{0 }$ values of SDMX  and SMX of 6.36 and 9.28, respectively).  [0307]  In terms of predicting composite activity, a reason› able indicator appears to be the sorption capacity of the  non-functionalized CNTs. In parallel to these flow through  systems, the sorption of each micropollutant in suspensions  (0.06 mg/L) of well-mixed (albeit still quite aggregated)  CNTs were examined. Removal in flow through generally  followed trends of relative micropollutant uptake observed  in CNT dispersions (FIG.  35),  once again implying that the  embedded CNTs are the primary active sorbent within the  porous composite materials. This raises the possibility of  using different types of functionalized CNTs known to  exhibit unique reactivity (e.g., N-doped CNTs were recently  noted to be better sorbents for it-donor aromatic compounds)  to produce composites with performance specifically tai› lored for target pollutants.  shown to contribute to uptake. However, flow-through  experiments clearly reveal that these materials are, indeed,  most effective toward more hydrophobic species, else they  require specific moieties (e.g., heterocyclic N groups) to  target for uptake. 