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In view of the characteristics of heavy metal and antibiotic compound pollution in the Pearl River Basin in Guangzhou. More scientifically modified cellulose, named HVUC, is characterized by multiple hydrophilic groups, long chains and large space and displays highly efficient adsorption of both Cd and sulfamethoxazole (SMZ) and good adaptability in a wide pH range and at high ion strength. Furthermore, the coadsorption mechanism was elaborated from multiple angles. Multiple adsorption experiments explained the competition and synergy effect in the adsorption process. The electrostatic potential maps indicated that HVUC had advantageous adsorption sites for both Cd and SMZ and that electrostatic interactions had the greatest impact on the adsorption of Cd and SMZ. The electron density and differential charge density images proved that Cd more easily overlapped electron clouds and transferred electrons with HVUC and that SMZ - and could act as a bridge for SMZ - . The equilibrium configuration indicated that the formation of Cd-SMZ - complexes led to the bending and folding of SMZ - , which was not conducive to overall adsorption when SMZ - was close to HVUC and could lead to the release of SMZ - when Cd was close to HVUC, which confirmed the proposed mechanism of complexation-decomplexation-complexation., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Phosphonic chelating fiber (PCCSF) as a novel adsorbent was produced through alkalization, etherification, amination and phosphonation, and then it was applied to adsorb sulfonamides (SAs), such as sulfadiazine (SD), sulfamonomethoxine (SMM) and sulfamethoxazole (SMZ). Specially, their adsorption behavior at different pH values was studied. As a result, PCCSF was provided with amino (NH 2 or NH) and PO(OH) 2 (PO) groups, and its equilibrium data were generally represented by both Langmuir and Freundlich models. Combining adsorbent-to-solution distribution coefficients (K d ) values and the effect of pH, the primary mechanism suggested that adsorption capacity of PCCSF was lower in strong acid and alkali solution, due to the electrostatic repulsion and hydrophobic interactions. By contrast, its adsorption affinity became more excellent at 3 < pH < 9 owing to the π-π electron-donor-acceptor (EDA) charge-assisted H-bond, Lewis acid-base interaction and charge-assisted H-bond (CAHB)., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

TEMPO-NaDCC-oxidized cellulose (TNOCS) with a large surface area and an abundance of carboxyl groups was used to remove heavy metal ions (Cd, Cu, and Pb) and their organic acid complexes [HM-OAs] (OAs, i.e., citric acid (CA) and propionic acid (PA)), and then reveal their adsorption behaviors. Taking Cd and CA as examples, the results showed that some of Cd ions were first adsorbed onto TNOCS, and then, the existence of [Cd-CA−] complexes formed a coordinated structure with preloaded Cd ions to serve as a bridge for combining TNOCS and [Cd-CA]. The maximum adsorption capacities of TNOCS for Cd and Cd-CA were 16.50 and 22.15 mg/g, respectively. Moreover, adsorption energies and molecular orbital distributions indicated that the adsorption capacity of TNOCS for [Cd-CA] was better than that for Cd alone. TNOCS can maintain greater than 90% adsorption capacity in five times regeneration experiments using EDTA, indicating that it is very efficient and stable. In addition, the electron density, deformation charge, and Mulliken charge distribution were confirmed that the electron transfer direction was from carboxyl groups to cadmium, whether it was cadmium ions or complexed cadmium. [ABSTRACT FROM AUTHOR]

2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) was oxidized to produce TEMPO-oxidized cellulose (TOCS) with a nanofunctionalized surface and abundant carboxyl groups. In a batch experiment, three pH values (2, 5 and 7), three modes (single, binary and multiple systems), and systems with inorganic and organic materials were applied to explore the adsorption of coexisting metals and antibiotics on TOCS. The adsorption capacity of TOCS was substantially influenced by these factors, and the adsorption behaviors were also different in these systems. In general, the coordination behaviors and electrostatic attraction between Cd(II) and carboxyl groups were identified as the mechanism employed by the single system, while hydrophobic interactions, π interactions, hydrogen bonding and pore filling contributed to the adsorption of sulfonamides (SAs) on TOCS in the binary system. The bridging effect was determined to be the key mechanism; i.e., most Cd(II) and SAs in the form of [SA-Cd] complexes interacted with carboxyl groups, especially in the presence of high concentrations of Cd(II) and SAs. These adsorption behaviors were determined quantitatively by performing density functional theory (DFT) calculations. In addition, TOCS showed excellent adsorption capacity in a more complex interference system, and the maximum adsorption capacity was 5.83 mg/g. • Corn stalk cellulose was surface nanofunctionalized by TEMPO system. • Single, binary and multiple systems were adopted in batch experiment. • pH and concentration of heavy metals or antibiotics change pathway of metal bridging. • The effect of inorganic ions and humic acid on Cd adsorption was studied. • DFT calculation was established for explained the adsorption mechanism. [ABSTRACT FROM AUTHOR]

For the treatment of heavy metal (HM)-polluted wastewater, an increasing number of novel and practical adsorbents have been developed and applied, especially cellulose-based materials, which have received increasing attention from researchers in recent years. This research has mainly focused on the influencing factors, thermodynamics, and kinetics of HM ion removal, and the associated mechanisms have been investigated theoretically. Density functional theory (DFT) is typically combined with experimental research to develop new materials and investigate their applications, and considerable progress has been achieved. Parameters calculated by DFT, such as the adsorption or interaction energy (E ads), frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP), natural bond orbitals (NBOs), electrostatic potential (ESP), and Mulliken population, play a crucial role in the study of adsorption behaviour. In this paper, the developments in DFT calculations of the properties of cellulose-based materials, as well as the applications and technical factors related to the removal of HM ions and HM composite pollutants, are reviewed. Furthermore, our team has focused on DFT approaches such as the sequential investigation of adsorption structure → functional groups → key elements. This sequential approach was used to assess the removal of HM ions and complexation–decomplexation–recomplexation processes related to the adsorption of HM composite pollutants to provide insights and methods supporting the development and substantive application of cellulose-based materials. [Display omitted] • Cellulose-based materials showed excellent performance in HMs-contained wastewater. • DFT calculations played a key role in quantitative analysis of adsorption mechanism. • DFT calculations can predict and provide key non-experimental information. • Our research explored a set of DFT calculations routes suitable for HMs removal. • DFT can reveal the mechanism such as complexation-discomplexation-recomplexation. [ABSTRACT FROM AUTHOR]

A new self-assembled cellulose (SACS) containing multi-functional amine, carboxyl and hydroxyl groups was successfully obtained through etherification, cross-linking and grafting processes. Then, the adsorption of sulfamethoxazole (SMZ) and Cd(II) onto SACS at pH values of 3, 5.7 and 7.5 was systematically investigated by batch experiments of single, sequential and binary systems, characterization and density functional theory (DFT) calculations. The presence of Cd(II) decreased the adsorption of SMZ because of hydrophilic site competition, while SMZ inversely increased the adsorption of Cd(II), which was attributed to bridging and especially to electrostatic shielding effects; moreover, both the inhibitory and synergistic effects were more obvious in the binary system and at a pH of 7.5. There was a dynamic balance between the inhibitory and synergistic effects that depended on the system, pH value and concentration ratio. DFT results further indicated that SMZ– more easily coordinated with Cd(II) at sulfonyl oxygen and nitrogen sites, and the cationic bridge of Cd(II) with SMZ– mainly occurred in the sequential system. Moreover, a complexation–decomplexation–complexation balance of SMZ– and Cd(II) probably occurred in the binary system. ga1 • Cellulose was assembled with amine, carboxyl and hydroxyl groups. • The cationic bridge of Cd(II) for SMZ– mainly occurred in the sequential system. • Both competition and the inhibitory effect were most obvious at a pH of 7.5. • SMZ– more easily coordinated with Cd(II) at sulfonyl oxygen and nitrogen sites. • A complexation–decomplexation–complexation balance occurred in the binary system. [ABSTRACT FROM AUTHOR]

A cellulose-polyacrylic acid-TiO 2 composite (CAT) with multiple carboxyl groups in the network structure and that could undergo ultrafast adsorption was successfully synthesized, and the adsorption capacity for cadmium(II) (Cd(II)) under optimal conditions was as high as 105 mg/g within 5 min. Additionally, CAT maintained the advantages of fast and efficient adsorption even when the concentrations of potentially interfering ions (NaCl, MgSO 4 , HA) were high. Importantly, 13 nonlinear kinetic models, including 6 empirical models and 7 diffusional models with their 5 error functions, were used to evaluate the adsorbent performance and mass transfer mechanism. As a result, regardless of whether interfering ions were present, the PNO model and Langmuir kinetics model were perceived as the best fit for the adsorption reaction and empirical model and mass transfer model, respectively. Adsorption at active centers was the rate limiting step for CAT. Moreover, the micromechanisms were also quantitatively explained with multiple DFT calculations, which illustrated ion exchange and electrostatic interactions with the oxygen atom on the introduced carboxyl group. [Display omitted] • Synthesis of ultrafast cellulose-TiO 2 composite adsorbent with multiple carboxyl. • CAT maintained fast and efficient adsorption of Cd (II) whether interfering ions. • 13 nonlinear kinetic models quantitatively evaluated adsorbent performance. • 5 error functions were summarized to determine the best fitting model. • DFT calculations further verified the main micromechanisms of ion exchange. [ABSTRACT FROM AUTHOR]