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Nitrate (NO 3 - ) is a ubiquitous contaminant in water and wastewater. Conventional treatment processes such as adsorption and membrane separation suffer from low selectivity for NO 3 - removal, causing high energy consumption and adsorbents usage. In this study, we demonstrate selective removal of NO 3 - in an electrosorption process by a thin, porous carbonized eggshell membrane (CESM) derived from eggshell bio-waste. The CESM possesses an interconnected hierarchical pore structure with pore size ranging from a few nanometers to tens of micrometers. When utilized as the anode in an electrosorption process, the CESM exhibited strong selectivity for NO 3 - over Cl - , SO 4 2- , and H 2 PO 4 - . Adsorption of NO 3 - by the CESM reached 2.4 × 10 -3  mmol/m 2 , almost two orders of magnitude higher than that by activated carbon (AC). More importantly, the CESM achieved NO 3 - /Cl - selectivity of 7.79 at an applied voltage of 1.2 V, the highest NO 3 - /Cl - selectivity reported to date. The high selectivity led to a five-fold reduction in energy consumption for NO 3 - removal compared to electrosorption using conventional AC electrodes. Density function theory calculation suggests that the high NO 3 - selectivity of CESM is attributed to its rich nitrogen-containing functional groups, which possess higher binding energy with NO 3 - compared to Cl - , SO 4 2- , and H 2 PO 4 - . These results suggest that nitrogen-rich biomaterials are good precursors for NO 3 - selective electrodes; similar chemistry can also be used in other materials to achieve NO 3 - selectivity., (Copyright © 2022. Published by Elsevier Ltd.)

Photocatalytic water treatment has significant potential to disinfect and degrade recalcitrant organic pollutants while minimizing the need to add chemicals, but current approaches have poor energy efficiency due, in part, to inefficient utilization of photo-generated reactive oxygen species (ROS). Organic coatings such as cyclodextrin (CD) can adsorb target contaminants and bring them close to the photocatalyst surface to enhance ROS utilization efficiency, but the coatings themselves are susceptible to ROS attack. Here, we report an ROS-resistant fluorinated CD polymer (CDP) that can both adsorb contaminants and resist degradation by ROS, yielding a more efficient material for "trap and zap" water treatment. We produced the CDP through condensation polymerization of β-cyclodextrin and tetrafluoroterephthalonitrile, resulting in a cross-linked, covalently bound CD film that is much more stable than prior approaches involving physi-sorption. We optimized the coating thickness on TiO 2 microspheres to improve the efficiency of contaminant degradation, and found that increasing the CDP content enhanced BPA adsorption but also occluded photocatalytic sites and hindered photocatalytic degradation. The optimum content of CDP was 5% by weight, and this optimal CDP-TiO 2 composition had a BPA adsorption capacity of 36.9 ± 1.0 mg g -1 compared with 24.1 ± 1.1 mg g -1 for CD-coated TiO 2 (CD-TiO 2 ) and 21.9 ± 1.5 mg g -1 for bare TiO 2 . CDP-TiO 2 exhibited minimal photoactivity loss after 1000 h of repeated use in DI water under UVA irradiation (365 nm, 3.83 × 10 -6  E L -1 s -1 ), and no release of organic carbon from the coating was detected. Photocatalytic treatment using CDP-TiO 2 only showed a small decrease in BPA removal efficiency in secondary effluent after four 3-h cycles, from 80.2% to 71.7%. In contrast, CD-TiO 2 and P25 removed only 29.8% and 6.2% of BPA after 4 cycles, respectively. Altogether, the CDP-TiO 2 microspheres represent promising materials for potential use in photocatalytic water treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Technologies capable of selective removal of target contaminants from water are highly desirable to achieve "fit-for-purpose" treatment. In this study, we developed a simple yet highly effective method to achieve calcium-selective removal in an electrosorption process by coating the cathode with a calcium-selective nanocomposite (CSN) layer using an aqueous phase process. The CSN coating consisted of nano-sized calcium chelating resins with aminophosphonic groups in a sulfonated polyvinyl alcohol hydrogel matrix, which accomplished a Ca 2+ -over-Na + selectivity of 3.5-5.4 at Na + :Ca 2+ equivalent concentration ratio from 10:1 to 1:1, 94 - 184% greater than the uncoated electrode. The CSN coated electrode exhibited complete reversibility in repeated operation. Mechanistic studies suggested that the CSN coating did not contribute to the adsorption capacity, but rather allowed preferential permeation of Ca 2+ and hence increased Ca 2+ adsorption on the carbon cathode. The CSN-coated electrode was very stable, showing reproducible performance in 60 repeated cycles., (Copyright © 2019 Elsevier Ltd. All rights reserved.)