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•Graphitization degree, defects, and basic sites increased with the temperature of biochar modification.•Acetaminophen degradation was enhanced increased with the temperature of ...biochar modification.•Graphitization degree, defects, C/O, C=O, and basicity were correlated with catalytic activity.•Persulfate was activated via persistent free radicals and delocalized electrons in graphitic structures.•Different electron donors activated persulfate for the biochars modified under different temperature.
In this study, a biochar (BC) derived from the pruning wastes of apple trees was thermally modified and was evaluated as a catalyst to explore an innovative strategy of valorization. The BC was thermally modified at 400, 550, and 700 °C, denoted as BC400, BC550, BC700, respectively. The removal of 50 mg/L acetaminophen (ACT) with 1.0 g/L biochars was <9.0% except for BC700 (19.1%), without an oxidant. However, it was greatly enhanced in the presence of 0.5 g/L sodium persulfate. The surface area normalized ACT removal rate constant increased from 6.56 × 10−5 min−1·m−2 for BC to 28.4 × 10−5 min−1·m−2 for BC700, and it was well-correlated with indicators of the degree of graphitization (sp2/sp3-C content), defects (ID/IG), C/O ratio, and C=O content. They were increased from 72.9% to 96.1%, 2.24 to 2.86, 4.9 to 12.1, and a negligible level to 3.9%, respectively, for BC and BC700. The electron paramagnetic resonance spectra and the characteristics of the biochars indicated that the ACT removal was attributed predominantly to SO4•− generation accepting electrons from persistent free radicals and the graphitic structures. The signal of SO4•− was the highest and dominant for BC700, which had the most developed graphitic structures, defects, and graphitic C=O with abundant (de)localized π electrons and non-bonding electrons. The results suggest that biochars can be excellent, environmentally friendly catalysts and that the activation mechanisms can be controlled by simple thermal modification to customize the performance for a wide variety of applications in various media, including water, soil, and sediments.
Selective filtration of dyes and inorganic salts is a challenge for the treatment of textile wastewater containing high salt contents. In this study, selective separation performance of PI/SiO2 ...nanofiltration (NF) membrane for dye/inorganic salt mixtures was substantially improved through directional modulation of its thermal treatment parameters after phase inversion. After thermal modification, the pore size, porosity and roughness were reduced, and the mechanical strength was improved. The PI/SiO2 membrane under optimized thermally-modified conditions (M6, heat treatment conditions: 50 °C for 8 min) possessed high porosity of 79.95%. Besides, the thermally-modified PI/SiO2 membrane revealed high water permeance of 152.87 L m−2 h−1·bar−1 with efficient rejection performance for a variety of typical dyes. In single dye filtration tests, the thermally-modified PI/SiO2 membrane displayed high rejection (>90%) for Coomassie Brilliant Blue (CBB), Congo Red (CR), Trypan Blue (TB) and Direct Black 38 (DB 38), and exhibited excellent permeance (84.21–133.76 L m−2 h−1·bar−1). In addition, the thermally-modified PI/SiO2 membrane could selectively separate dyes and inorganic salts. The membrane exhibited high dye rejection (>90%) and low inorganic salt rejection (<10%) for the filtration tests of CR + NaCl/Na2SO4 and CBB + NaCl/Na2SO4 mixed solutions (2 g L−1). In particular, the permeances of the thermally-modified PI/SiO2 membrane (89.45–130.21 L m−2 h−1·bar−1) were higher than those of many contemporary NF membranes used for the same type of dye/inorganic salt separation. In conclusion, the present study presents a simple, inexpensive and effective thermal modification means, which shows great promise in the selective filtration of industrial dye wastewater.
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•Heat treatment parameters of PI/SiO2 membranes after phase inversion were optimized.•Thermal modification reduced the roughness, pore size and porosity of the membranes.•The thermally modified membrane exhibited high permeance and rejection of four dyes.•The thermally modified membrane can selectively separate dye and inorganic salt.•The thermally modified membrane showed high permeance for dye/salt separation.
Gasified fine ash (GFA) exhibits poor reactivity due to its low carbon content and high ash content, which restricts its potential for combustion utilization. To enhance the reactivity of GFA, we ...employed a circulating fluidized bed (CFB) as a thermal modification unit (TMU) to thermally modify GFA from different entrained-flow gasifiers. We also experimentally investigated the impact of equivalence ratio, temperature, and feedstock moisture content on the thermal modification of GFA. After thermal modification of GFA, the pore structure of modified fine ash (MFA) was significantly improved, the proportion of active sites in residual carbon increased, and the proportion of graphitized structures decreased. An appropriate increment in the equivalence ratio increased the number of carbon active sites in MFA. A good thermal modification effect was found on the GFA produced by different types of gasification furnaces. The temperature rise promoted gasification reaction in the TMU and restricted carbon conversion, thus decreasing the consumption of combustible residual carbon. An increase of water content in the GFA improved the pore structure, but excessive water caused adverse effects.
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•Increased combustion performance of GFA is achievable through thermal modification.•Studied impact of ER, T, and M modification conditions on combustion performance.•Mechanism of thermal modification to enhance reactivity of GFA has been elucidated.
•Heat treatment imposed a significant effect on the surface color of the bamboo.•The compositional properties of the heat-treated bamboo are investigated.•Microstructure of heat-treated bamboo are ...inspected.•Chemical structural changes are verified by FTIR analysis.
Fast growth and high mechanical properties are the key commercial value of bamboo used in various applications. However, the high contents of starch and sugar in the bamboo may cause issues of biodegradation. Heat treatment provides the effective method to modify the chemical properties of bamboo. This study here investigated the effects of heat treatment technology on modifying the surface and chemical properties of moso bamboo (Phyllostachys edulis). The bamboo heat treatment was conducted in different conditions; specifically, three treatment media (i.e., air, nitrogen, and linseed oil), four treatment temperatures (i.e., 150, 170, 190, and 210 °C), and three durations (i.e., 1, 2, and 4 h) were explored. The results revealed that the treatment temperature and duration imposed a significant effect on the surface color and contact angle of the bamboo. In other words, higher treatment temperatures induced darker surface colors and larger contact angles, which ensure favorable hydrophobicity of the bamboo. Moreover, by inspecting the microstructure of the bamboo, this study discovered that the bamboo treated at high temperatures were prone to intense damage to its tissue structures, particularly the parenchyma cells. In addition, Fourier-transform infrared (FTIR) spectroscopy was conducted to examine heat-induced changes in the chemical components of the bamboo. The results of the FTIR spectroscopy revealed that the intensity of the characteristic absorption peaks of polysaccharides decreased with increasing treatment temperatures, whereas the intensity of lignin peaks demonstrated an opposite changing trend. Through a quantitative analysis of the chemical components of the treated bamboo, the content of holocelluloses, hemicelluloses, and α-celluloses of the treated bamboo was determined. The analytical results were highly consistent with that of the FTIR spectroscopy.
Bamboo culms of Dendrocalamus strictus (Roxb.) were subjected to thermal modification at different treatment temperatures of 160, 180 and 200 °C under partial vacuum. Control and thermally modified ...bamboos were converted into strips and crushed strands to produce laminated (LBL) and scrimber (SBL) composites respectively using melamine formaldehyde adhesive. Effects of treatment temperatures on various properties including decay resistance were studied and characterized using XRD and FTIR. Average EMC was reduced to different levels depending on severity of thermal treatments. Density of composite was improved significantly and increasing treatment temperatures exhibited greater anti-swelling efficiency. Dark colour of modified bamboo was influenced by treatment parameters, while microstructure was not much affected. Most of mechanical parameters of composites produced from bamboo modified were enhanced. However, higher temperature (≥ 200 °C) showed detrimental effects on strength. Modified bamboo exhibited greater decay resistance against two rotting fungi. Some changes in crystalline structure and certain functional groups were observed after thermal modification. With desirable improvements in aesthetic and quality parameters, composites from thermally modified bamboo may be considered as ecological alternative to preservative treated materials. The LBL and SBL may, therefore, be utilized in production of valued-added lifestyle artifact in allied bamboo industry sectors.
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•Laminated and scrimber composites prepared from thermally modified bamboo and MF resin.•Density, ASE and decay resistance of composites were significantly improved.•Bamboo composites exhibited significant variations in different mechanical properties.•Composites from thermally modified bamboo found suitable for structural applications.
Lactic acid (LA), citric acid (CA), and glycerol (G) are renewable and environmentally friendly chemicals that could improve the qualities of short-rotation teak (SRT) woods. This study investigated ...the effect of thermal and chemical modification using 20% aqueous solutions (w/w) of LA, CA, and G and their mixtures in the same composition on physical and mechanical properties of SRT teak wood. The impregnation process was initiated by vacuum process for 1 h and pressure (12.2 bar) for 2 h, followed by thermal (150 °C) treatment for 6 h on the SRT wood samples after being removed from the vacuum-pressure tube. Retention (R), weight percent gain (WPG), density (D), anti-swelling efficiency (ASE), leachability (WL), modulus of elasticity (MOE), and modulus of rupture (MOR) were measured. FTIR spectrometry and SEM analyses were performed. The wood impregnated with a mixture of 10% LA + 10% CA provided the highest ASE values of 50.1%, and the lowest leaching resistance of 1.54%. Based on wood strengths (MOE and MOR) and physical properties, as well as supported by FTIR and SEM analysis, the use of 10% LA + 10% CA is the most prospective as an impregnant formula for SRT wood modification of this research.
Thermal conductivity of asphalt concrete determines the temperature distribution in asphalt pavements and thus affects viscoelastic modulus of asphalt concrete and the microclimate environment near ...pavement surface. This paper developed an innovative model to evaluate thermal conductivity of asphalt concrete with heterogeneous microstructure. The three-dimensional (3-D) microstructures of asphalt concrete was simulated with different-sized aggregates and air voids randomly distributed in asphalt binder. A hierarchical multi-scale finite element (FE) modeling approach was used to simulate the steady heat transfer process for predicting the effective thermal conductivity of asphalt concrete. The results were validated with experiment data reported in the literature. With the developed model, the effects of aspect ratios and orientation angles of aggregate, conductive filler, and specimen size on thermal conductivity of asphalt concrete were analyzed. Results show that the orientation angle and aspect ratio of aggregate have combined effects on thermal conductivity of asphalt concrete, depending on the orientation of the longest diagonal of aggregate with respect to the direction of heat conduction. The thermal conductivity of asphalt concrete is affected by the content and shape of graphite filler for thermal modification. On the other hand, it is recommended that the specimen size should be at least five times the maximum aggregate size for measuring thermal conductivity. The larger ratio of specimen size to maximum aggregate size is needed when the maximum aggregate size increases. In general, the developed model can be used as an analysis tool to guide the mix design of asphalt concrete for thermal optimization.
•Generate three-dimensional microstructure of asphalt concrete with three-phases.•Simulate steady heat transfer to predict thermal conductivity of asphalt concrete.•Validate finite-element simulation results with experimental data.•Evaluate effects of aggregate characteristics, conductive filler, and specimen sizes.
•Investigating the effect of high-volume WCP on the properties of sustainable recycled mortar.•Utilizing thermal modification to improve the performance of mortar with high-volume WCP.•Suggesting the ...optimal thermal modification temperature for WCP and its mortar.
Utilizing waste concrete powder (WCP) to prepare eco-friendly cementitious materials provides an effective approach to recycling concrete waste, and thus, this work focuses on the properties and modification of sustainable recycled mortar including high-volume WCP. The WCP with an irregular microstructure consists of abundant inert components, while the thermal modification treatment on WCP promotes the formation of new active components. Incorporating untreated WCP decreases the hydration products and increases the pore size, but the thermal modification on WCP benefits the micro-properties of newly-prepared paste. The addition of WCP prolongs the setting time, while the thermal modification on WCP up to 900 ℃ shortens the setting time; besides, the mortar with WCP after 1200 ℃ activation has excellent fluidity and shrinkage resistance. The mechanical strength decreases and water transport increases following the growing substitution rate of WCP, and an obvious degeneration appears as high-volume WCP incorporates. At the identical replacement ratio of WCP, the properties of mortar with 300–900 ℃ thermally-modified WCP are superior to those of mortar including untreated WCP. For instance, the compression strength and capillary absorption coefficient of mortar including 50% WCP after 900 ℃ activation are 26.4% higher and 46.1% lower relative to mortar including untreated WCP. However, there is hardly apparent improvement on the performance of newly-prepared mortar including WCP modified by 1200 ℃.
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•Thermal modification method was used for original copper slag.•Phase transformation of raw copper slag can be favorable for NOx removal.•The active components for NOx removal in ...modified copper slag was illustrated.•The possible reaction pathway of simultaneous removal of SO2 and NOx was proposed.
The high desulfurization capacity has been obtained in the wet process when using industrial waste solids as novel absorbents, however, the high-efficient NOx removal remains as a challenge. Here we report a novel wet method with highly active slurry containing CaO-thermally modified copper slag and KMnO4 oxidant to remove NOx and SO2 simultaneously. We demonstrate a best removal efficiency of 84.4% and 100% for NOx and SO2, respectively. The enhanced efficiency was achieved with 30 wt% CaO and calcinated at 800 °C for 200 min. Interestingly, the NOx removal efficiency was primarily depending on calcination temperature, while CaO dosage and calcination time had an insignificant influence. The increasing NOx removal efficiency could be attributed to the optimized phase structure of copper slag and the higher alkalinity of the slurry. Specifically, the phase structure of the original copper slag was effectively converted by CaO calcination, resulting in a decrease in the contents of Fe(II)-containing substances including Fe3O4, Fe2SiO4, and metal sulfides. Through composition simulation experiments with raw copper slag, Fe2O3, CuFe2O4, and CuO in the modified equivalent were identified to be responsible for the NOx removal. On the contrary, Ca3Fe2(SiO4)3 formed at higher calcination temperatures was detrimental to NOx removal efficiency. With characterizing the modified copper slag samples via XRD before and after reaction along with analyzing the spent solution with ion chromatography (IC), we proposed a corresponding reaction mechanism of simultaneous removal of NOx and SO2.
