N-Doped Biochar as a New Metal-Free Activator of Peroxymonosulfate for Singlet Oxygen-Dominated Catalytic Degradation of Acid Orange 7.

In this paper, using rice straw as a raw material and urea as a nitrogen precursor, a composite catalyst (a nitrogen-doped rice straw biochar at the pyrolysis temperature of 800 °C, recorded as NRSBC800) was synthesized by one-step pyrolysis. NRSBC800 was then characterized using XPS, BET, TEM and other technologies, and its catalytic performance as an activator for permonosulfate (PMS) to degrade acid orange 7 (AO7) was studied. The results show that the introduction of N-doping significantly improved the catalytic performance of NRSBC800. The NRSBC800/PMS oxidation system could fully degrade AO7 within 30 min, with the reaction rate constant (2.1 × 10 -1 min-1) being 38 times that of RSBC800 (5.5 × 10-3 min-1). Moreover, NRSBC800 not only had better catalytic performance than traditional metal oxides (Co3O4 and Fe3O4) and carbon nanomaterial (CNT) but also received less impact from environmental water factors (such as anions and humic acids) during the catalytic degradation process. In addition, a quenching test and electron paramagnetic resonance (EPR) research both indicated that AO7 degradation relied mainly on non-free radical oxidation (primarily singlet oxygen (1O2)). A recycling experiment further demonstrated NRSBC800's high stability after recycling three times.

Rice husk biochar modified-CuCo2O4 as an efficient peroxymonosulfate activator for non-radical degradation of organic pollutants from aqueous environment.

A series of rice husk biochar (RHBC) modified bimetallic oxides were prepared using a simple pyrolysis method to activate peroxymonosulfate (PMS) for the degradation of acid orange G (OG). The results demonstrated that 50 mg L-1 OG was completely decomposed by 1 mM PMS activated with 100 mg L-1 RHBC-CuCo2O4 within 15 min at initial pH 3.4. The OG degradation rate constant k of RHBC-CuCo2O4/PMS (0.95 × 10-1 min-1) was five times greater than that of CuCo2O4/PMS (0.19 × 10-1 min-1), suggesting that the introduction of RHBC significantly improved the activity of bimetallic oxides. The effects of the initial pH, catalyst dosage, PMS concentration and reaction temperature on OG removal were also studied. The degradation products of OG were analysed using a gas chromatography-mass spectrometer (GC-MS). Electron paramagnetic resonance (EPR) and quenching experiments showed that singlet oxygen (1O2) was the main active species. The RHBC-CuCo2O4/PMS oxidation system is not only unaffected by inorganic anions (Cl-, NO3 -, HCO3 -) and humic acid (HA), but also could remove other typical pollutants of acetaminophen (ACT), sulfathiazole (STZ), rhodamine B (RhB), and bisphenol A (BPA). These findings show that RHBC-CuCo2O4 has great potential for practical applications in the removal of typical organic pollutants.

CoMn2O4 Catalyst Prepared Using the Sol-Gel Method for the Activation of Peroxymonosulfate and Degradation of UV Filter 2-Phenylbenzimidazole-5-sulfonic Acid (PBSA).

In this study, a bimetallic oxide catalyst of cobalt-manganese (CoMn2O4) was synthesized using the sol-gel method, and it was then characterized using a variety of techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption isotherms. The obtained novel catalyst, i.e., CoMn2O4, was then used as an activator of peroxymonosulfate (PMS) for the catalytic degradation of a commonly-used UV filter, 2-phenylbenzimidazole-5-sulfonic acid (PBSA) in water. The effects of various factors (e.g., catalyst dosage, PMS concentration, reaction temperature, and pH) in the process were also evaluated. Chemical scavengers and electron paramagnetic resonance (EPR) tests showed that the •OH and SO4•- were the main reactive oxygen species. Furthermore, this study showed that CoMn2O4 is a promising catalyst for activating PMS to degrade the UV filters.

Prediction of supercooled liquid vapor pressures and n-octanol/air partition coefficients for polybrominated diphenyl ethers by means of molecular descriptors from DFT method.

The molecular geometries of 209 polybrominated diphenyl ethers (PBDEs) were optimized at the B3LYP/6-31G level with Gaussian 98 program. The calculated structural parameters were taken as theoretical descriptors to establish two novel QSPR models for predicting supercooled liquid vapor pressures (P(L)) and octanol/air partition coefficients (K(OA)) of PBDEs based on the theoretical linear solvation energy relationship (TLSER) model, respectively. The two models achieved in this work both contain three variables: most negative atomic partial charge in molecule (q(-)), dipole moment of the molecules (mu) and mean molecular polarizability (alpha), of which R(2) values are both as high as 0.997, their root-mean-square errors in modeling (RSMEE) are 0.069 and 0.062 respectively. In addition, the F-value of two models are both evidently larger than critical values F(0.05) and the variation inflation factors (VIF) of variables herein are all less than 5.0, suggesting obvious statistic significance of the P(L) and K(OA) predicting models. The results of Leave-One-Out (LOO) cross-validation for training set and validation with external test set both show that the two models obtained exhibited optimum stability and good predictive power. We suggest that the QSPRs derived here can be used to predict accurately P(L) and K(OA) for non-tested PBDE congeners from Mono-BDEs to Hepta-BDEs and from Mono-BDEs to Hexa-BDEs, respectively.

QSPR to aqueous solubility (lgSw) of alkyl(1-phenylsulfonyl) cycloalkane-carboxylates using MLSER model and ab initio.

Based on the modified linear solvation energy relationship (MLSER) model and quantum chemical descriptors computed at HF/STO-3G, HF/LANL2DZ, B3LYP/LANL2D and B3LYP/6-31G* levels, different quantitative structure-property relationships (QSPRs) to the aqueous solubility (lgSw) of 28 alkyl(1-phenylsulfonyl) cycloalkane-carboxylates were obtained. It is suggested that the eight models developed in the present study all have good correlation and relatively small error, in which the model with four variables, the most positive formal charge (qH+), molecular volume (Vi), melting point (mp) and free energy (G0) as descriptors obtained from B3LYP/6-31G* level, exhibited the best optimum correlation (r2=0.9743 and q2=0.9644, respectively) and smallest error, and thus are advantageous to other models. It was also found that molecular volume is the most significant factor influencing lgSw. The lgSw increased with increasing qH+ and G0, while decreased with increasing Vi and mp. The MLSER model achieved from ab initio calculation is better than that from the semiempirical AM1 method.

[Quantitative relationship between gas chromatographic retention indices and structural parameters of polychlorinated naphthalenes].

The structural and thermodynamic properties of 76 polychlorinated naphthalenes (PCNs) were fully computed at B3LYP/6-31G* level. Both structural and thermodynamic parameters of PCNs obtained were consequently taken as theoretical descriptors and correlated with their gas chromatographic retention indices (RI), so as to develop the relevant quantitative structure-retention relationship (QSRR) regression model (model I) with r2 of 0.9957, which possesses high correlation, high predictive power and clear physical interpretations. Secondly, another linear QSRR model (model II) was achieved by employing the number and position of chlorine substitution as descriptors, of which r2 was 0.9967, and also the main factors affecting the retention time of PCNs were investigated.