Immobilization of laccase on organic–inorganic nanocomposites and its application in the removal of phenolic pollutants

Polydopamine-functionalized nanosilica was synthesized using an inexpensive and easily obtainable raw material,mild reaction conditions,and simple operation.Subsequently,a flexible spacer arm was introduced by using dialdehyde starch as a cross-linking agent to bind with laccase.A high loading amount(77.8 mg∙g^(‒1))and activity retention(75.5%)could be achieved under the optimum immobilization conditions.Thermodynamic parameters showed that the immobilized laccase had a lower thermal deactivation rate constant and longer half-life.The enhancement of thermodynamic parameters indicated that the immobilized laccase had better thermal stability than free laccase.The residual activity of immobilized laccase remained at about 50.0%after 30 days,which was 4.0 times that of free laccase.Immobilized laccase demonstrated excellent removal of phenolic pollutants(2,4-dichlorophenol,bisphenol A,phenol,and 4-chlorophenol)and perfect reusability with 70% removal efficiency retention for 2,4-dichlorophenol after seven cycles.These results suggested that immobilized laccase possessed great reusability,improved thermal stability,and excellent storage stability.Organic–inorganic nanomaterials have a good application prospect for laccase immobilization,and the immobilized laccase of this work may provide a practical application for the removal of phenolic pollutants.

Complete removal of phenolic contaminants from bismuth-modified TiO2 single-crystal photocatalysts

Exploring low-cost and highly active photocatalysts is very urgent to accomplish complete removal of phenolic contaminants and overcome the limitations of the existing photocatalysts.In this study,we designed and synthesized noble metal-free TiO2 photocatalysts by introducing bismuth nanoparticles as modifiers of a TiO2 single crystal(Bi-SCTiO2).The Bi-SCTiO2 can make full use of the synergistic effect of a small band overlap and low charge carrier density(Bi)with a high conductivity(single crystal),significantly boosting the separation and migration of the photogenerated charge pairs.Therefore,the Bi-SCTiO2 photocatalyst exhibits a significantly enhanced degradation rate(12 times faster)of 4-nitrophenol than a TiO2 single crystal under simulated sunlight irradiation.Notably,the complete removal of phenolic contaminants is achieved in various water matrices,which not only successfully overcomes the incomplete degradation in many reported photocatalytic systems,but also manifests a significant practical potential for sewage disposal.Therefore,this work presents a new insight in designing and constructing noble metal-free decorated semiconductor single-crystal photocatalysts with excellent activity and cyclability.

Intelligent laser-induced graphene sensor for multiplex probing catechol isomers

Herein,we unveil the intelligent detection of multiple catechol isomers in complex environments utilizing both laser-induced graphene(LIG)and artificial neural network(ANN).The large scale-up manufacturing of LIG-based sensors(LIGS)with three-electrode configuration on polyimide(PI)is achieved by direct laser-writing and screen-printing technologies.Our LIGS shows excellent electrochemical performance toward catechol isomers,i.e.,hydroquinone(1,4-dihydroxybenzene,HQ),catechol(1,2-dihydroxybenzene,CT),and resorcinol(1,3-dihydroxybenzene,RC),with a low limit of detection(LOD)(CC,0.079μmol/L;HQ,0.093μmol/L;RC,1.18μmol/L).Moreover,the ANN model is developed for machine-intelligent to predict concentrations of catechol isomers under an interfering environment via a single LIGS.Using six unique parameters extracted from the differential pulse voltammetry(DPV)response,the machine learning-based regression provides a coefficient of correlation with 0.998 and is able to correctly predict the total and individual concentrations in complex river samples.Hence,this work provides a guide for the preparation and application of LIGS via facile and cost-efficient mass production and the development of an intelligent sensing platform based on the ANN model.

Carbonate-induced enhancement of phenols degradation in CuS/peroxymonosulfate system: A clear correlation between this enhancement and electronic effects of phenols substituents

This study investigated the enhancement effects of dissolved carbonates on the peroxymonosulfate-based advanced oxidation process with CuS as a catalyst.It was found that the added CO_(3)^(2−)increased both the catalytic activity and the stability of the catalyst.Under optimized reaction conditions in the presence of CO_(3)^(2−),the degradation removal of 4-methylphenol(4-MP)within 2 min reached 100%,and this was maintained in consecutivemulti-cycle experiments.The degradation rate constant of 4-MP was 2.159 min^(−1),being 685%greater than that in the absence of CO_(3)^(2−)(0.315 min−1).The comparison of dominated active species and 4-MP degradation pathways in both CO_(3)^(2−)-free and CO_(3)^(2−)-containing systems suggested thatmore CO_(3)·^(−)/^(1)O_(2) was produced in the case of CO_(3)^(2−)deducing an electron transfer medium,which tending to react with electron-richmoieties.Meanwhile,Characterization by X-ray photoelectron spectroscopic and cyclic voltammetrymeasurement verified CO_(3)^(2−)enabled the effective reduction of Cu^(2+)to Cu^(+).By investigating the degradation of 11 phenolics with different substituents,the dependence of degradation kinetic rate constant of the phenolics on their chemical structures indicated that there was a good linear relationship between the Hammett constantsσp of the aromatic phenolics and the logarithm of k in the CO_(3)^(2−)-containing system.This work provides a new strategy for efficient removal of electron-rich moieties under the driving of carbonate being widely present in actual water bodies.

Mesopolymer modified with palladium phthalocyaninesulfonate as a versatile photocatalyst for phenol and bisphenol A degradation under visible light irradiation

A novel versatile photocatalyst, FDU-PdPcS, was prepared by immobilizing palladium phthalocyaninesulfonate （PdPcS） onto the FDU-15 mesopolymer via multi-step chemical modification processes involving chloromethylation of the FDU-15 mesopolymer first with chloromethyl methyl ether, a subsequent amination reaction with ethylenediamine, and finally modification with palladium phthalocyaninesulfonate via ionic interaction. The obtained FDU-PdPcS photocatalyst was characterized by the X-ray diffraction （XRD）, UV-Vis spectrosopy and inductively coupled plasma （ICP） techniques. This photocatalyst not only affords a high dispersion of monomeric PdPcS molecules, which may further be stabilized by the π-electron of benzene rings of FDU-15, but also provides a number of diamino groups inside the mesopores, which could be advantageous for the photodegradation of phenolic pollutants. In photodegradation studies of phenolic pollutants, the FDU-PdPcS catalyst exhibited excellent visible light photocatalytic activity and reusability. The photodegradation products of phenol and bisphenol A were investigated by the gas chromatoghraphy-mass spectrometry （GC-MS） technique. The results showed that the photodegradation products were composed of carboxylic acids and CO2. Isopropanol, sodium azide and benzoquinone were used as hydroxyl radical （OH.）, singlet oxygen （1O2） and superoxide radical （O2.-） scavengers, respectively. The results suggested that 1O2 and O2. were the prominent active species during the photodegradation process. A possible mechanism for the photodegradation of phenol was also discussed.

Direct and Simultaneous Determination of Phenol, Hydroquinone and Nitrophenol at Boron-Doped Diamond Film Electrode

The electrochemical characteristics of multi-component phenolic pollutants, such as phenol （Ph）, hydroquinone （HQ） and 4-nitrophenol （4-NP）, were investigated on boron-doped diamond （BDD） film electrode by differential pulse voltammetry （DPV） technique. A simple and feasible platform was accordingly established for the direct and simultaneous determination of these three phenolic pollutants. Results showed that, Ph, HQ and 4-NP gave obvious oxidation peaks on BDD electrode at the potential of 1.24, 0.76 and 1.52 V, respectively. Each of them displayed good linear relationship between their oxidation peak currents and their corresponding concentrations in a rather wide range coexisting with one or two of the other phenolic pollutants. The detection limits of Ph, HQ and 4-NP were estimated to be as low as 1.82×10^-6, 1.67×10^-6 and 1.44×10^-6 mol·L^-1, respectively. Therefore, a promising direct and simultaneous electrochemical determination method of multi-component phenolic pollutants in wastewater samples was constructed successfully on BDD electrode with advantages being rapid, simple, convenient, sensitive, in situ and inexpensive.