The biological NO3- removal process might be accompanied by high CO2 emissions and operation costs. Capacitive deionization (CDI) has been widely studied as a very efficient method to purify water. Here, a porous carbon material with a tunable nitrogen configuration was developed. Characterization and density functional theory calculation show that nitrogenous functional groups have a higher NO3- binding energy than Cl-, SO42-, and H2PO4-. In addition, the selectivity of NO3- is improved after the introduction of micropores by using the pore template. The NO3- ion removal and selectivity of MN-C-12 are 4.57 and 3.46-5.42 times that of activated carbon (AC), respectively. The high NO3- selectivity and electrosorption properties of MN-C-12 (the highest N content and micropore area) are due to the synergistic effect of the affinity of nitrogen functional groups to NO3- and microporous ion screening. A CDI unit for the removal of nitrogen from municipal wastewater was constructed and applied to treat wastewater meeting higher discharge standards of A (N: 15 mg L-1) and B (N: 20 mg L-1) ((GB18918-2002), China). This work provides new insights into enhanced carbon materials for the selective electrosorption of wastewater by CDI technology.

The inherent defects of bimetallic metal-organic frameworks (B-MOFs) play a significant role in enhancing their performance. The combination of resin with MOFs provides a shortcut for optimizing their structure and adsorption performance. This study developed a simple strategy to control the inherent defects of materials by adjusting the Zr/La precursor ratio to enhance the adsorption performance of Zr-La-MOFs@201 for organophosphorus. To achieve this, we prepared a series of X-Zr-La-MOFs@201 and investigated the impact of different ratios on the degree of defects. Among them, 2-Zr-La-MOFs@201 exhibited a maximum adsorption capacity for organophosphorus of 123.6 mg/g, which is 1.25 and 3.08 times compared to UIO-66@201 and D201, respectively. 31P NMR and TGA results indicated that the performance enhancement primarily stemmed from the increased formation of M-P bonds, which differs from the commonly mentioned hydroxyl substitution. DFT calculations showed that the presence of defects effectively reduced the reaction activation energy. In actual water treatment, the maximum treatment capacity of this material reached 5000 BV. This impressive performance demonstrates the potential of Zr-La-MOFs@201 for practical applications in other fields, providing a benchmark for the development of new materials.

Metal organic framework (MOF)-based adsorbents are appealing for removing low-concentration phosphates with interfering ions in wastewater purification, a new strategy developed to maintain the good activity of metal sites. Here, ZIF-67 was immobilized onto the porous surface of anion exchange resin (D-201) with a high loading amount of 22.0 wt % by a modifiable Co(OH)2 template. We observed that the removal rate of low-concentration phosphate (2 mg P/L) by ZIF-67/D-201 nanocomposites was 98.6%, and more than 90% phosphate adsorption capacity was still maintained, with 5 times molar concentration of interfering ions in the solution. Moreover, after six times of regeneration by solvothermal reaction in the ligand solution, the structure of ZIF-67 was better preserved in D-201 with more than 90% phosphate removal rate. ZIF-67/D-201 could be employed effectively in fixed-bed adsorption runs. By the analysis of experiment and characterization, we found that during the adsorption-regeneration process of ZIF-67/D-201 for phosphate, reversible structural transformation of ZIF-67 and Co3(PO4)2 occurred in D-201. In general, the study reported a new method to develop MOF adsorbents for wastewater treatment.

Adsorption process was usually torn between higher affinity and easier regeneration. Herein, for removing phosphate from low concentration solution, a new strategy was developed to break this tradeoff by metal organic frameworks (MOFs) confined in resins. For comparison, a series of metal oxide modified resins were prepared as adsorbents together with MOFs modified resins (transformation from corresponding oxides). MIL-101(Fe) presents higher adsorption capacity (41.79 mg/g) than Oxide(Fe)@201(36.07 mg/g), as well as high antiinterference ability with removal efficiency of 99.8% (2 mg/L phosphate), even if the loading amounts of iron in Oxide(Fe)@201 is almost twice of that in MIL-101(Fe)@201. Instrumental analysis and molecular dynamics simulations show that the higher adsorption affinity is mainly due to direct interaction between Fe3+ and phosphate via the formation of Fe-O-P, leading to much lower adsorption binding energy (E-ads) of phosphate on MIL-101(Fe)@201 (-42.48 kcal/mol) than Oxide(Fe)@201; In desorption process, the MOFs structure can be stably restored with push of organic salt and high temperature (60 degrees C) around neutral pH due to the reversible structural transformation of MOFs. Moreover, MIL-101(Fe)@201 can continuously purify wastewater containing low concentration phosphate in fixed bed system after multiple regeneration, the water treatment capacity remained above similar to 3000 BV and the regenerants can be intermittently recycled with precipitation of calcium phosphate from the solutions.

The catalytic oxidation of toxic organic pollutants in water requires enhanced efficiency for commercial applications. A ZnO nanorod array grown on a carbon fiber cloth (CFC) serves as the zinc source to ensure that the Ni/ZIF-8/ZnO nanoreactor is constructed. The Ni/ZIF-8/ZnO/CFC nanoreactor efficiently activates peroxymonosulfate (PMS) for bisphenol A (BPA) degradation owing to its high density of active sites, high adsorbability, and dispersibility structure, which concentrates catalytic and adsorptive sites within a confined space. Experimental and theoretical calculations clearly show that the introduction of Ni is beneficial for improving the adsorption of BPA and the activation of PMS. The synergistic mechanism of BPA adsorption-PMS activation is also investigated, and the degradation pathway of BPA is examined. Moreover, a filter catalytic unit is constructed using Ni/ZIF-8/ZnO/CFC to achieve a continuous zero discharge of BPA, which is convenient for nanocatalyst recycling. This study aims to develop a new strategy for the removal of emerging organic pollutants from water using a system with strong adsorption and catalytic capabilities.