Simultaneous Removal of Cr(VI) and Phenol from Water Using Silica-di-Block Polymer Hybrids: Adsorption Kinetics and Thermodynamics.

Heavy metal ions and organic pollutants often coexist in industrial effluents. In this work, silica-di-block polymer hybrids (SiO2-g-PBA-b-PDMAEMA) with two ratios (SiO2/BA/DMAEMA = 1/50/250 and 1/60/240) were designed and prepared for the simultaneous removal of Cr(VI) and phenol via a surface-initiated atom-transfer radical polymerization process using butyl methacrylate (BA) as a hydrophobic monomer and 2-(Dimethylamino)ethylmethacrylate (DMAEMA) as a hydrophilic monomer. The removal efficiency of Cr(VI) and phenol by the hybrids reached 88.25% and 88.17%, respectively. The sample with a larger proportion of hydrophilic PDMAEMA showed better adsorption of Cr(VI), and the sample with a larger proportion of hydrophobic PBA showed better adsorption of phenol. In binary systems, the presence of Cr(VI) inhibited the adsorption of phenol, yet the presence of phenol had a negligible effect on the adsorption of Cr(VI). Kinetics studies showed that the adsorption of Cr(VI) and phenol fitted the pseudo-second-order model well. Thermodynamic studies showed that the adsorption behavior of Cr(VI) and phenol were better described by the Langmuir adsorption isotherm equation, and the adsorption of Cr(VI) and phenol were all spontaneous adsorptions driven by enthalpy. The adsorbent still possessed good adsorption capacity for Cr(VI) and phenol after six adsorption-desorption cycles. These findings show that SiO2-g-PBA-b-PDMAEMA hybrids represent a satisfying adsorption material for the simultaneous removal of heavy metal ions and organic pollutants.

Efficient photodegradation of cefixime catalyzed by a direct Z-scheme CQDs-BiOBr/CN composite: Performance, toxicity evaluation and photocatalytic mechanism.

Development of low-cost, nontoxic, highly efficient performance photocatalyst for water pollution control engineering is critical for environmental remediation. In this contribution, a direct Z-scheme heterojunction based on C quantum dot (CQDs), bismuth oxybromide (BiOBr) and bulk graphitic carbon nitride (g-C3N4, CN) (CQDs-BiOBr/CN composite) with outstanding photocatalytic activity and good reusability is successfully fabricated though a hydrothermal procedure for cefixime antibiotic photodegradation. In particular, the CQDs-BiOBr/CN composite possess the best cefixime degradation effect, the degradation rate is about 92.82% within 120 min. The enhancement photocatalytic activity of CQDs-BiOBr/CN can be ascribed to the improved light-harvest ability, the excellent adsorption performance, the efficient charge transportation and separation capability. A possible degradation pathway of cefixime is proposed base on HPLC-MS. Toxicity experiments demonstrate that the antibiotic activity of cefixime is effectively deactivated after degradation process, and which is no toxic effect for Rye seeds in deionized water. The CQDs-BiOBr/CN also displays the excellent photoactivation activity towards Escherichia coli (E. coli). Reactive-species-trapping experiments show that hydroxyl radical (⋅OH) and superoxide radical (⋅O2-) are the active reactive species in the photodegradation process. The CQDs-BiOBr/CN composite demonstrate an effective potential practical application in antibiotic pollutants degradation from wastewater.

Multifunctional Silica-Based Amphiphilic Block Copolymer Hybrid for Cu(II) and Sodium Oleate Adsorption in Beneficiation Wastewater.

Beneficiation wastewater contains various types of pollutants, such as heavy metal ions and organic pollutants. In this work, a silica-based amphiphilic block copolymer, SiO2-g-PBMA-b-PDMAEMA, was obtained by surface-initiated atom transfer radical polymerization (SI-ATRP) for Cu(II) and sodium oleate adsorption in beneficiation wastewater, using butyl methacrylate (BMA) as a hydrophobic monomer and 2-(dimethylamino)ethylmethacrylate (DMAEMA) as a hydrophilic monomer. FTIR, TGA, NMR, GPC, XRD, N2 adsorption-desorption isotherms and TEM were used to characterize the structure and morphology of the hybrid adsorbent. The introduction of PBMA greatly increased the adsorption of sodium oleate on SiO2-g-PBMA-b-PDMAEMA. Adsorption kinetics showed that the adsorption of Cu(II) or sodium oleate on SiO2-g-PBMA-b-PDMAEMA fitted the pseudo-second-order model well. Adsorption isotherms of Cu(II) on SiO2-g-PBMA-b-PDMAEMA were better described by the Langmuir adsorption isotherm model, and sodium oleate on SiO2-g-PBMA-b-PDMAEMA was better described by the Freundlich adsorption isotherm model. The maximum adsorption capacity of Cu(II) and sodium oleate calculated from Langmuir adsorption isotherm equation reached 448.43 mg·g-1 and 129.03 mg·g-1, respectively. Chelation and complexation were considered as the main driving forces of Cu(II) adsorption, and the van der Waals force as well as weak hydrogen bonds were considered the main driving forces of sodium oleate adsorption. The adsorbent was recyclable and showed excellent multicomponent adsorption for Cu(II) and sodium oleate in the mixed solution. SiO2-g-PBMA-b-PDMAEMA represents a satisfying adsorption material for the removal of heavy metal ions and organic pollutants in beneficiation wastewater.

Preparation and Application of a Magnetic Oxidized Micro/Mesoporous Carbon with Efficient Adsorption for Cu(II) and Pb(II).

Water pollution is a worldwide problem that requires urgent attention and prevention and exceeding use of heavy-metal ions is one of the most harmful factors, which poses a serious threat to human health and the ecological environment. In this work, a magnetic oxidized micro/mesoporous carbon (MOMMC) was prepared for the easy separation of Cu(II) and Pb(II) from water. The dual-template method was used to prepare micro/mesoporous carbon using sucrose as the carbon source, silica nanoparticles formed by tetraethyl orthosilicate as the microporous templates, and triblock copolymer F127 as the mesoporous template. MOMMC was obtained by oxidation using potassium persulfate and then magnetized through in situ synthesis of Fe3O4 nanoparticles. FTIR, TG-DSC, XRD, TEM, SEM, nitrogen adsorption-desorption isotherms, zeta potential, and VSM were used to confirm the synthetic process, structure, and basic properties of MOMMC. The high-saturation magnetization (59.6 emu·g-1) of MOMMC indicated its easy and fast separation from water by an external magnetic field. Kinetics studies showed that the adsorption of Cu(II) and Pb(II) on MOMMC fit the pseudo-second-order model well. Isotherm studies showed that the adsorption behavior of Cu(II) was better described by the Langmuir model, and the adsorption behavior of Pb(II) was better described by both Langmuir and Redlich-Peterson models. MOMMC obtained efficient adsorption for Cu(II) and Pb(II) with the large adsorption capacity of 877.19 and 943.40 mg·g-1 according to the Langmuir adsorption isotherm equation, and a better selectivity for Pb(II) was observed in competitive adsorption. MOMMC still possessed a large adsorption capacity for Cu(II) and Pb(II) after three adsorption-desorption cycles. These findings show that MOMMC represents an excellent adsorption material for the efficient removal of heavy-metal ions.

Correction: Two Ln-based metal-organic frameworks based on the 5-(1H-1,2,4-triazol-1-yl)-1,3-benzenedicarboxylic acid ligand: syntheses, structures, and photocatalytic properties.

[This corrects the article DOI: 10.1039/D0RA07159E.].

Two Ln-based metal-organic frameworks based on the 5-(1H-1,2,4-triazol-1-yl)-1,3-benzenedicarboxylic acid ligand: syntheses, structures, and photocatalytic properties.

Two new metal-organic frameworks (MOFs) having the formula [Ln2(H2O)3(L)3·3H2O] n (Ln = Sm for MOF-Sm and Tb for MOF-Tb) have been synthesized solvothermally by reacting LnCl3·6H2O with 5-(1H-1,2,4-triazol-1-yl)-1,3-benzenedicarboxylic acid (H2L) and characterized. Single crystal X-ray analyses for MOF-Sm and MOF-Tb revealed that both MOFs are isostructural and display a (6,8)-connected 3D structure with a point symbol of (35·44·66)(35·46·517). The natures of weak interactions existing in both MOFs have been assessed using Hirshfeld surface analyses and fingerprint plots. The utility of MOF-Sm as a photocatalyst for the safe photodegradation of the model aromatic dye methyl violet (MV) is also checked. The photocatalysis results showed that MOF-Sm offers reasonable photocatalytic degradation of this dye. The plausible photocatalytic mechanism of MOF-Sm aided photocatalysis has been explained with the help of band gap calculations using density of states (DOS) and partial DOS plots.

Morphology-controlled Fabrication of SnO2 /ZnO Nanocomposites with Enhanced Photocatalytic Performance.

In this work, a series of novel SnO2 /ZnO nanocomposites with different morphologies were fabricated via a facile hydrothermal technique followed by calcination in air. The morphological, structural and photocatalytic properties of the SnO2 /ZnO nanocomposites were studied using different methods. The results showed that the synthesized nanocomposites possessed crystal phases of wurtzite hexagonal phase ZnO and tetragonal rutile phase SnO2 . In addition, the morphologies of SnO2 /ZnO nanocomposites strongly depended on the molar ratios of Sn and Zn. Compared with ZnO and SnO2 , the SnO2 /ZnO nanocomposites exhibited considerably higher degradation efficiency for the photodegradation of methylene blue and quinolone antibiotics under mercury lamp irradiation. The SZ-2 nanospheres exhibited the highest degradation efficiency of 95.81%, which was about 2.63 times higher than that of ZnO nanoparticles. Moreover, the trapping experiments confirmed that ˙OH played the dominant role in MB degradation. Finally, the charge carriers potential transfer pathway and photocatalytic degradation mechanism were put forward. This study provides an economical way to prepare hybrid nanocomposites with controlled morphology for practical applications in the photocatalytic degradation of organic dyes and residual antibiotics.

A Novel Gold Nanoprobe for a Simple Electrochemiluminescence Determination of a Prostate-specific Antigen Based on a Peptide Cleavage Reaction.

A novel gold nanoprobe for a sensitive and simple determination of a prostate-specific antigen (PSA) was designed on the basis of homogeneous detection and a peptide cleavage reaction. The gold nanoprobe (AuNPs-peptide-Ru1) consisted of a specific peptide tagged with a ruthenium(II) complex (Ru1) and gold nanoparticles (AuNPs) conjugated with the peptide via the strong Au-S bond between the AuNPs surface and the thiol group of the peptide. The electrochemiluminescence (ECL) enzymatic-cleavage-reaction-based bioanalytic system based on homogeneous detection has overcome shortcomings from a complicated fabrication process of traditional electrodes. In the presence of the target PSA, it specifically cleaved the peptide of the AuNPs-peptide-Ru1, and the ECL signal substance (Ru1) part dissociated from AuNPs-peptide-Ru1. This resulted in an increase in the ECL intensity. The ECL biosensor could detect PSA concentrations in the range from 1.0 × 10-12 to 1.0 × 10-9 g/mL, the detection limit was 4.0 × 10-13 g/mL. The assay with the advantages of a simple method for PSA was selective and fast. It is superior to the immunoassay, and is a promising strategy to develop biosensors based on enzymatic cleavage including electrochemistry and optics.

Deactivation and Regeneration of NaTaO3 Photocatalyst in Cooperating Dehydrogenation Coupling of Isopropanol and Hydrogenation Coupling of Acetone Reaction System.

Photocatalyst activity is influenced by many factors, such as adsorption of by-products, runoff of surface hydroxyl groups and carriers. In this study, a simple and efficient photocatalyst regeneration method was developed. Results indicated that NaTaO3 photocatalyst lost its photoactivity after three cycles of reaction that involves coupling of isopropanol and hydrogenation coupling of acetone reaction system. Runoff of Na on the surface was the main reason for the deactivation of NaTaO3 photocatalyst. After hydrothermal treatment of the deactivated NaTaO3 with 10 m NaOH at 180°C for 12 h, its photocatalytic activity was restored to the original level. The photocatalytic activity remained stable even after 10 cycles.