[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). 

[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• 

[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. 

[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 

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. 

[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. 

[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). 

[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. 

[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). 

