Kinetic and Thermodynamic Characteristics of Torrefied Acer palmatum.

The goal of this research was to investigate the effects of torrefying temperature (220, 260, and 300 °C) on the physicochemical properties, kinetics, thermodynamic parameters, and reaction processes of Acer palmatum (AP) during the pyrolysis process. The kinetics of raw materials and torrefied biomass were studied by using three kinetic models, and the main function graph approach was employed to find the reaction mechanism. The torrefied biomass produced at temperatures of 220 °C (AP-220), 260 °C (AP-260), and 300 °C (AP-300) was thermogravimetrically analyzed at four different heating rates (5, 10, 15, and 20 °C/min). In comparison to the raw material, the average activation energy of torrefied biomass declined with increasing temperature, from 174.13 to 84.67 kJ/mol (FWO), 172.52 to 81.24 kJ/mol (KAS and DAEM). The volatile contents of AP and AP-220 are higher than those of AP-260 and AP-300, indicating that the random nucleation model occupies the central position. Compared with the raw biomass, the average Gibbs free energy (ΔG) of torrefied biomass increased from 157.97 to 195.38 kJ/mol. The mean enthalpy change (ΔH) during the torrefaction process is positive, while the mean entropy change (ΔS) of the torrefaction of biomass is negative, decreasing from 16.93 to -151.53 kJ/mol (FWO) and from 14.36 to -156.06 kJ/mol (KAS and DAEM). Overall, the findings provide a comprehensive understanding of the kinetics and improved features of torrefied biomass as a high-quality solid fuel.

Synthesis of CeO2 hollow microspheres with oxidase-like activity and their application in the catalytic degradation of p-nitrophenol.

CeO2 materials have received wide attention given their oxidase-like activity without the need for an unstable oxide substrate in the catalytic process. Nevertheless, their application and mechanism in the catalytic oxidation of refractory organic pollutants needs further study. Herein, CeO2 hollow microspheres (HMS) with an intrinsic oxidase-like activity were synthesised via a template-free hydrothermal method and their effectiveness in degrading p-nitrophenol(p-NP) was investigated. HMS showed a maximum p-NP degradation rate of 76.5% at a CeO2 dosage of 40 mg, 2 h reactive time, at 30°C and pH of 4.8 when the concentration of p-NP was 20 mg L-1. The catalytic activity of CeO2 HMS also exhibited good thermal stability and reusability. These results provide strong evidence that CeO2 HMS can be utilised as an oxidase mimetic for the efficient catalytic degradation of refractory organic pollutants. A possible mechanism for the degradation of p-NP is also discussed.

Effect of factors on decolorization of azo dye methyl orange by oxone/natural sunlight in aqueous solution.

PURPOSE: The oxone process for azo dye decolorization has drawbacks such as difficulties with reuse, risks of secondary pollution, and high costs associated with UV irradiation. This study aims to explore the use of oxone for decolorization in the absence of catalyst and under natural sunlight conditions (i.e., oxone/natural sunlight system) and evaluate the impacts of operating parameters (reagent dosage, initial methyl orange (MO) concentration, and initial pH) and coexisting substances (humic acid, NO(3)(-), metal ions) on the system's decolorization efficiency. METHODS: Four levels of operating parameters were configured under a Taguchi L(16) orthogonal array design to examine their effects on decolorization efficiency. Fractional factional design was then used to derive the optimal combination of operating parameters, under which the effects of coexisting substances at various concentrations were examined. In addition, H(2)O(2), CH(3)OH, and (CH(3))(3)COH were used to derive the possible reaction mechanisms in the oxone/sunlight system, while ultrasonic power was used to shorten the reaction time. RESULTS: In the oxone/sunlight system, (1) the MO decolorization efficiency reaches 96.4% under the optimal operating conditions: initial concentration, 100 mg L(-1); initial pH 6.04; dosage of reagent, 3 mmol L(-1); and reaction time, 30 min. (2) Coexisting substances do not affect the overall decolorization efficiency. (3) The decolorization of MO in the oxone/sunlight system takes place mainly via oxidation by SO(4)·â». (4) Ultrasonic irradiation could remarkably accelerate the MO decolorization process. CONCLUSION: Effective for MO decolorization, the oxone/sunlight system improves over the traditional oxone process with advantages of lower costs and avoiding secondary pollution by catalyst.

Factors that have an effect on degradation of diclofenac in aqueous solution by gamma ray irradiation.

PURPOSE: Gamma ray irradiation is considered as an effective way to degrade diclofenac. However, due to the extensive coexisting substances in natural waters, the use of gamma ray irradiation for degradation is often influenced by multiple factors. The various factors that affect degradation efficiency, such as initial diclofenac concentration, initial pH, and the concentration of the additives including H(2)O(2) (·OH radical promoter), CH(3)OH (·OH radical scavenger), thiourea (·OH, H·, and e (aq) (-) scavenger), humic acid, and NO(3)(-) (coexisting substances in natural waters), are investigated. Furthermore, possible intermediate products are identified and corresponding transformation pathways are proposed. METHODS: Degradation experiments were performed in a 50-mL airtight Pyrex bottle loaded with 25 mL of diclofenac solutions at various initial concentrations of 20.5, 30.4, and 50.1 mg L(-1). The radiation doses were controlled at 0, 0.3, 0.5, 0.7, and 1.0 kGy. RESULTS: Study results indicate that: (1) The degradation efficiency of diclofenac decreases with the increase of its initial concentration. (2) The degradation efficiency is higher under acidic conditions than in neutral and alkaline media. (3) The results obtained when H(2)O(2), CH(3)OH, and thiourea were added show that the degradation of diclofenac takes place via two pathways: oxidation by ·OH radicals and reduction by e (aq) (-) and H·. (4) The extensive coexisting substances in natural waters, such as humic acid and NO(3)(-), do not affect the degradation efficiency. Based on the identified intermediates, it is proposed that transformation pathways are initiated mainly by H·, e (aq) (-) , and ·OH. CONCLUSION: Gamma ray irradiation effectively degrades diclofenac.