Removal of methyl orange wastewater by Ugi multicomponent reaction functionalized UiO-66-NS.

The efficient and rapid removal of organic dyes from wastewater remains a complex and challenging task. In this study, UiO-66-NH2 was prepared by solvothermal synthesis, and then, UiO-66-NS was prepared by compounding L-cysteine with UiO-66-NH2 via the Ugi reaction for the efficient removal of methyl orange. UiO-66-NS was prepared by the addition of 1 mmol L-cysteine and showed good adsorption of methyl orange with 92.00% removal. Pseudo-second-order kinetics and Langmuir isotherms more accurately described the adsorption process of UiO-66-NS on methyl orange, which indicated that the adsorption process was dominated by monolayer adsorption of chemical reactions, and the maximum adsorption amounts of UiO-66-NS on methyl orange were 242.72 mg/g at 298 K. In addition, UiO-66-NS exhibited ultrahigh stability in acidic, neutral, and alkaline media (pH = 3-10), but its adsorption of methyl orange after 5 cycles was only 59.53% of the maximum adsorption amount. The adsorption mechanism is primarily electrostatic adsorption of UiO-66-NS with methyl orange, hydrogen bonding, and π-π interactions. This atomically economical Ugi multicomponent reaction provides new ideas for the preparation of structurally designable adsorbents with excellent performance.

Removal of copper ions by functionalized biochar based on a multicomponent Ugi reaction.

Copper is widely present in the natural environment and inevitably poses a risk to both human health and the natural environment. Biochar is an inexpensive, clean and sustainable sorbent material that can be used as a resource for copper removal, and there is interest in new ways to chemically treat biochar to tune its unique properties and modify its atomic structure. In this study, biochar was oxidized, and then polyethyleneimine (PEI) modified chitosan and carboxylated biochar were economically compounded through a multicomponent Ugi reaction to effectively remove Cu(ii). PEI enhances the adsorption of Cu(ii) within an optimum solution pH range of 3.5-5.5. The adsorption process follows a pseudo-second-order kinetic model. When the dosage of BC-NH2 was 4 g L-1 and the temperature was 303 K, the maximum adsorption capacity calculated by the Langmuir model was 26.67 mg g-1. The adsorption process of Cu(ii) on BC-NH2 was heat-trapping and spontaneous. BC-NH2 showed good selectivity for K+ and Mg2+, and BC-NH2 desorbed by NaOH showed better adsorption performance than H2SO4 in the adsorption-desorption cycle. Characterization by SEM, EDS, BET, FTIR, TGA and XPS showed successful coupling and that the amide group of BC-NH2 had chelated with Cu(ii). This atomically economical multicomponent Ugi reaction provides a new option for preparing composite materials that effectively remove heavy metals.

A novel adsorbent TEMPO-mediated oxidized cellulose nanofibrils modified with PEI: Preparation, characterization, and application for Cu(II) removal.

This study describes the preparation of a novel adsorbent based on cellulose nanofibrils by first TEMPO mediated oxidation and then PEI grafting (TOCN-PEI) for heavy metal removal. FTIR results demonstrated the successful introduction of the adsorption functional groups (carboxyl and amino groups), and the elemental analysis and acid base titration were used to quantify the contents of these introduced groups. The kinetics curve suited the pseudo-second-order model better and the equilibrium data well fitted the Langmuir model, with the maximum Cu(II) uptake of 52.32mgg(-1). Kinetic study showed that the PEI grafting increased the initial adsorption rate of the TOCN-PEI compared with the adsorbents without PEI. Thermodynamic study was carried out through isothermal titration calorimetry (ITC) measurement and the binding reaction was found to be exothermic and driven by enthalpy change. The adsorption process by TOCN-PEI was pH dependent, and decreasing pH would lead to desorption of Cu(II) ions, thus make the reuse of the absorbent more convenient through adsorption-desorption cycles.

Reactive oxygen species (ROS) generated by cyanobacteria act as an electron acceptor in the biocathode of a bio-electrochemical system.

The enhanced electricity generation in a biocathode bio-electrochemical system (BES) with Microcystis aeruginosa IPP as the cathodic microorganism under illumination is investigated. The results show that this cyanobacterium is able to act as a potential cathodic microorganism under illumination. In addition, M. aeruginosa IPP is found to produce reactive oxygen species (ROS) in its growth in the BES. ROS, as more competitive electron acceptors than oxygen, are utilized prior to oxygen. The BES current is substantially reduced when the ROS production is inhibited by mannitol, indicating that the ROS secreted by the cyanobacterium play an important role in the electricity generation of such a biocathode BES. This work demonstrates that the ROS released by cyanobacteria benefit for an enhanced electricity generation of BES.

Nutrient removal and energy production in a urine treatment process using magnesium ammonium phosphate precipitation and a microbial fuel cell technique.

Urine pretreatment has attracted increasing interest as it is able to relieve the nitrogen and phosphorus overloading problems in municipal wastewater treatment plants. In this study, an integrated process, which combines magnesium ammonium phosphate (MAP) precipitation with a microbial fuel cell (MFC), is proposed for the recovery of a slow-release fertilizer and electricity from urine. In such a two-step process, both nitrogen and phosphorus are recovered through the MAP process, and organic matters in the urine are converted into electricity in the MFCs. With this integrated process, when the phosphorus recovery is maximized without a dose of PO(4)(3-)-P in the MAP precipitation process, removal efficiencies for PO(4)(3)-P and NH(4)(+)-N of 94.6% and 28.6%, respectively, were achieved with a chemical oxygen demand (COD) of 64.9% accompanied by a power output of 2.6 W m(-3). Whereas removal efficiencies for PO(4)(3)-P and NH(4)(+)-N of 42.6% and 40%, respectively, and a COD of 62.4% and power density of 0.9 W m(-3) were obtained if simultaneous recovery of phosphorus and nitrogen was required through dosing with 620 mg L(-1) of PO(4)(3-)-P in the MAP process. This work provides a new sustainable approach for the efficient and cost-effective treatment of urine with the recovery of energy and resources.

Enhanced reductive degradation of methyl orange in a microbial fuel cell through cathode modification with redox mediators.

A model azo dye, methyl orange (MO), was reduced through in situ utilization of the electrons derived from the anaerobic conversion of organics in a microbial fuel cell (MFC). The MO reduction process could be described by a pseudo first-order kinetic model with a rate constant of 1.29 day(-1). Electrochemical impedance spectroscopic analysis shows that the cathode had a high polarization resistance, which could decrease the reaction rate and limit the electron transfer. To improve the MO reduction efficiency, the cathode was modified with redox mediators to enhance the electron transfer. After modification with thionine, the polarization resistance significantly decreased by over 50%. As a consequence, the MO decolorization rate increased by over 20%, and the power density was enhanced by over three times. Compared with thionine, anthraquinone-2, 6-disulfonate modified cathode has less positive effect on the MFC performance. These results indicate that the electrode modification with thionine is a useful approach to accelerate the electrochemical reactions. This work provides useful information about the key factors limiting the azo dye reduction in the MFC and how to improve such a process.

Direct electricity recovery from Canna indica by an air-cathode microbial fuel cell inoculated with rumen microorganisms.

Aquatic plants are widely used for phytoremediation, and effective disposal methods should be pursued for their utilization and to avoid further environmental pollution problems. This study demonstrated that, using an air-cathode microbial fuel cell (MFC) inoculated with rumen microorganisms, electricity could be directly produced with a maximum power density of 0.405 W/m(3) from Canna indica (canna), a lignocellulosic aquatic plant rich in cellulose, hemicellulose, and lignin, without pretreatment. The mechanisms of the Canna indica degradation in the MFC were elucidated through analyzing the changes of canna structure and intermediates, that is, soluble sugars and volatile fatty acids (VFAs), in the electricity generation process. The results showed that lignin was partially removed and more cellulose became exposed on the sample surface during the electricity generation in the MFC. The electron transfer in this MFC was mainly completed through electron shuttling via self-produced mediators. This work presents an attempt to understand how complex substrates like aquatic plants are decomposed in an MFC during electricity generation. It might, hopefully, provide a promising way to utilize lignocellulosic biomass for energy generation.