Investigating the potential of structurally defective UiO-66 for Sb (V) removal from tailing wastewater.

Antimony contamination of tailings from the mining process remain attracted a great amount of concern. In this study, defective UiO-66-X crystal materials are rationally constructed using trifluoroacetic acid and hydrochloric acid as modulators for the removal of Sb(V) from actual tailing sand leachates. XRD and TG characterizations reveal that the number and kind of defects in UiO-66 are influenced by the type of modulators and the addition of trifluoroacetic acid makes UiO-66-TFA contain both cluster and ligand defects. Adsorption experiments show that UiO-66 and UiO-66-HCl achieve 100% removal of Sb(V) at pH 7.5 of the tailing sand leachate, and up to 90% removal of Sb(V) by the three materials at pH 2.5. It is noteworthy that the removal rate of Sb(V) by UiO-66-HCl is still satisfactory even under strongly acidic conditions at pH 0.5, with good potential for practical applications. Four kinetic models are used to fit the adsorption data and the analysis shows that the mechanism of Sb(V) adsorption by three adsorbent is all pseudo-second order and chemisorption acts as an important role in the adsorption process. In addition, the fixed bed adsorption experiments show that the material exhibit good prospects for practical applications.

Numerical study on supercontinuum generation by different optical modes in AsSe2-As2S5 chalcogenide microstructured fiber.

We investigate supercontinuum generation (SCG) in AsSe2-As2S5 chalcogenide microstructured optical fibers (MOFs) pumped by different optical modes. The influence on SCG by different optical modes including the fundamental and high-order modes is analyzed numerically. The evolution of the supercontinuum (SC) is investigated by changing the pump wavelength (2120, 2580, and 3280 nm) and peak power (from 200 to 1000 W) of each optical mode (LP01,LP11,LP31) in the MOFs with different fiber lengths. SCG in MOFs with different core diameters is also simulated. The different optical modes cause the variation of the chromatic dispersion profile and the effective nonlinearity, which induces different mechanisms of the SCG and changes the spectral range. The maximum SC spectral range covers 12.931 µm from 1.389 to 14.320 µm when pumped by the LP11 mode with the peak power of 1000 W at 3280 nm. The simulated results will be instructive for the experimental SCG up to the midinfrared waveband longer than 10 µm.

Theoretical investigation on mid-infrared cascaded Raman fiber laser based on tellurite fiber.

A numerical simulation of third-order cascaded Raman fiber laser based on tellurite fiber at the 2-5 µm waveband is presented. The Raman fiber laser can be optimized with the most suitable tellurite fiber length of 0.5-1.0 m and the most reasonable reflectivity of the third-order Stokes output FBG32 of 10%-20%. We demonstrate numerically that the third-order Stokes wave can reach the maximum average power of 45.2 W and the maximum optical conversion efficiency of 45.2%, corresponding to the FBG32 reflectivity of 10% and the tellurite fiber length of 0.3 m with the attenuation of 0.85 dB/m, when pumped by 2 µm light with the average power of 100 W. Our simulated results provide valuable theoretical guidance for the design and experiment of tellurite Raman fiber laser at a mid-infrared waveband.

Quantifying sodium hypochlorite content in hypochlorite-based disinfectants via phase-conversion headspace technique.

In this work, a novel and efficient approach for sodium hypochlorite analysis is proposed via phase-conversion headspace technique, which is based on the gas chromatography (GC) detection of generated carbon dioxide (CO2) from the redox reaction of sodium hypochlorite with sodium oxalate. The data obtained by the proposed method suggest the high detecting precision and accuracy. In addition, the method has low detection limits (limit of quantification (LOQ) = 0.24 µg/mL), and the recoveries of added standard ranged from 98.33 to 101.27 %. The proposed phase-conversion headspace technique is efficient and automated, thereby offering an efficient strategy for highly efficient analysis of sodium hypochlorite and related products.

Donor-acceptor moiety functionalized covalent organic frameworks for boosting charge separation and H2 photogeneration.

Covalent organic frameworks (COFs) have a broad prospect to be used as a photocatalytic platform to convert solar energy into valuable chemicals due to their tunable structures and rich active catalytic sites. However, constructing COFs with tuned sp2-carbon donor-acceptor moiety remains an enormous challenge. Herein, we synthesized two new fully π-conjugated cyano-ethylene-linked COFs containing benzotrithiophene as functional group by Knoevenagel polycondensation reaction. The accetpor 2,2'-bipyridine unit in BTT-BpyDAN-COF skeleton favored the formation of a intermolecular specific electron transport pathway with the donor benzotrithiophene, and thereby promoted charge separation and transfer efficiency. Specifically, a donor-acceptor (D-A) type BTT-BpyDAN-COF exhibited high hydrogen evolution rate of 10.1 mmol g-1h-1 and an excellent apparent quantum efficiency of 4.83 % under visible light irradiation.

Experimental Study of Salicylic Acid as a Calcium Sulfate Dihydrate Scale Inhibitor, Analyzed from Surface Properties and Crystal Growth.

Static and dynamic experiments were carried out to study the antiscale performance of salicylic acid (SA) to calcium sulfate dihydrate (CSD) scale. The CSD scale formed in the reuse of processing of wastewater of phosphorite flotation. The scale surface physicochemical properties have been investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ζ potential, and contact angle measurements. The antiscale mechanisms of SA to CSD were studied from surface properties and crystal growth. The results showed that the scale inhibition efficiency of SA to CSD reached 98.9% (6 mg/L) under static conditions. Under dynamic conditions, the faster the fluid velocity, the less CSD formed. The order of scaling capability on different material surfaces was 20#CS > 304SS > PC > PE. The growth of CSD was inhibited by SA resulting in the surface becoming porous. The deprotonated SA could easily interact with the Ca2+ to make the CSD surface potential negative. The wettability properties of the CSD are greatly improved when the contact angle is reduced. The surface tension values of CSD without and with 6 mg/L SA are 19.06 and 240.69 mN/m2, respectively. SA as a scale inhibitor can significantly inhibit crystallization of CSD.

A critical review on adsorption and recovery of fluoride from wastewater by metal-based adsorbents.

Rapid industrialization is deteriorating water quality, and fluoride pollution in water is one of the most serious environmental pollution problems. Adsorption technology is an efficient and selective process for removing fluoride from aqueous solutions using adsorbents. Metal-based adsorbents synergize the advantages of fast adsorption, high adsorption capacity, and excellent selectivity to effectively remove fluoride from water bodies, promising to satisfy environmental sustainability requirements. This paper reviews the metal-based adsorbents: iron-based, aluminum-based, lanthanum-based, cerium-based, titanium-based, zirconium-based, and multi-metal composite adsorbents, primarily focusing on the adsorption conditions and fluoride removal capacities and discusses prospects and challenges in the synthesis and application of metal-based adsorbents. This paper aims to stimulate new thinking and innovation in developing the next generation of sustainable adsorbents.