Catalytic degradation of crystal violet and methyl orange in heterogeneous Fenton-like processes.

Metals-loaded (Fe3+, Cu2+ and Zn2+) activated carbons (M@AC) with different loading ratios (0.1%, 0.5%, 1%, 5% and 10%) were prepared and employed for catalytic degradation of dye model compounds (crystal violet (CV) and methyl orange (MO)) in wastewater by heterogeneous Fenton-like technique. Compared with Cu@AC and Zn@AC, 0.5% Fe3+ loaded AC (0.5Fe@AC) had better catalytic activity for dyes degradation. The effects of dyes initial concentration, catalyst dosage, pH and hydrogen peroxide (H2O2) volume on the catalytic degradation process were investigated. Cyclic performance, stability of 0.5Fe@AC and iron leaching were explored. Degradation kinetics were well fitted to the pseudo-second-order model (Langmuir-Hinshelwood). Almost complete decolorization (99.7%) of 400 mg L-1 CV was achieved after 30 min reaction under the conditions of CV volume (30 mL), catalyst dosage (0.05 g), H2O2 volume (1 mL) and pH (7.7). Decolorization of MO reached 98.2% under the same conditions. The abilities of pyrolysis char (PC) of dyeing sludge (DS) and metal loaded carbon to remove dye pollutants were compared. The intermediate products were analyzed and the possible degradation pathway was proposed. This study provided an insight into catalytic degradation of triphenylmethane- and aromatic azo-based substances, and utilization of sludge char.

Microwave pyrolysis of oily sludge under different control modes.

The effects of temperature and power on product distribution and characteristics of oily sludge (OS) pyrolysis were investigated in a microwave reactor. The maximum oil yield was 72.55 wt% at 550 °C and 71.47 wt% at 800 W, respectively. X-ray photoelectron spectroscopy (XPS) indicated that C-C and C-O were the main forms of carbon in OS char (OC). The sulfur (S) content in OC increased as the temperature/power rose, implying that S might exist in the form of inorganics or OC had S retention ability. In temperature control mode, the changes of functional groups on OC surface were more sensitive. The maximum hydrocarbon content in oil was 14.56% at 350 °C and 13.40% at 900 W, respectively. The contents of oxygenated compounds and heterocycles in oil from temperature control mode were higher. The CO yield increased with increasing temperature/power, reaching the maximum of 9.60 wt% at 650 °C and 7.75 wt% at 900 W, respectively. Compared with power control mode, it seemed that more heavy metals (HMs) were retained in OC in temperature control mode. The Er of HMs were at the clean level and RI indicated the HMs in OC had a low environmental risk.

Microwave-assisted pyrolysis of oily sludge from offshore oilfield for recovery of high-quality products.

Microwave pyrolysis of oily sludge (OS) was investigated in this study. In this case, the highest oil yield (85.93 wt%) was achieved at 500 °C. The molar ratio of H/C was lower for OS char (OC) at higher pyrolysis temperatures, indicating good stability of OC owing to high degree of carbonization and aromaticity. Then, iodine adsorption value of OC reached maximum (531.2 mg/g) at 750 °C. While methylene blue (MB) uptake slightly increased with temperature and reached maximum (384.08 mg/g) at 850 °C. In order to improve the quality of pyrolysis products, different catalysts were employed in OS pyrolysis. The maximum content (64.31%) of aromatic hydrocarbon was found in PO500-10ß. In addition, ß-zeolite also reduced oxygenates content in oil, beneficial for stability of oil products. The gas products from catalytic pyrolysis were abundant in CO and CH4, and KOH achieved the highest CO (5.9 wt%), CH4 (16.9 wt%) and H2 (2.4 wt%) yields. Finally, a reaction mechanism pathway for OS pyrolysis was proposed to show the production routes of gas, liquid, and solid products.

Petroleum oil and products recovery from oily sludge: Characterization and analysis of pyrolysis products.

Oily sludge (OS) has attracted special interest because of its hazardous nature and high potential as an energy resource. This study investigated the oil recovery from OS by thermal cracking and catalytic pyrolysis. The oil yield increased when the temperature exceeded 450 °C and reached a maximum (76.84 wt%) at 750 °C. Catalysts significantly improved the quality of oil produced during catalytic pyrolysis. Aromatic hydrocarbons were dominant (10.01-52.69%) in pyrolysis oil (PO) from OS catalytic pyrolysis, and the catalysts significantly reduced the presence of oxygen heterocycles. In addition, KOH and CaO reduced the ID (D-band peak intensity)/IG (G-band peak intensity) of OS char (OC) and increased the degree of graphitization. Owing to its higher iodine adsorption value and methylene blue (MB) adsorption value, OC exhibits potential as an adsorbent. The environmental assessment and potential applications of OC, along with possible reaction mechanisms and kinetic characteristics, are also discussed.

Microwave-assisted catalytic pyrolysis of waste printed circuit boards, and migration and distribution of bromine.

Microwave-assisted pyrolysis (MAP) of waste printed circuit boards (WPCB) was performed to investigate the characteristics of pyrolysis product and Br fixation. Pyrolysis conversion increased with increasing temperature, reaching 93.3 % at 650 °C. However, increasing heating time did not exhibit remarkable influence on pyrolysis conversion. At 350 °C, phenols were main compounds in the oil accounting for 91.15 %. As the temperature increased to 650 °C, polycyclic aromatic hydrocarbons and monocyclic aromatic hydrocarbons (except phenols) increased to 20.55 % and 19.03 %, respectively. Meanwhile, the total content of CO2, CO, CH4 and H2 in the non-condensable gases increased significantly. Addition of ZSM-5 and kaolin promoted the recombination reaction of pyrolysis products, increased the relative percentage of monocyclic aromatic hydrocarbons (except phenols) and C11-C20 compounds in the oil, and reduced non-condensable gases. The oxygen bomb-ion chromatography was used to evaluate the Br content of pyrolysis residues. Higher pyrolysis temperature enhanced transfer of Br to pyrolysis gas. K2CO3, Na2CO3 and NaOH reacted with hydrogen bromide to generate KBr and NaBr, which significantly improved the Br fixation efficiency of pyrolysis residues (i.e. from 29.11%-99.80%, 96.39 % and 86.69 %, respectively) and reduced Br content in pyrolysis gas.

Torrefaction subsequent to pelletization: Characterization and analysis of furfural residue and sawdust pellets.

Torrefaction integrated with pelletization has gained increasingly interest as it enhances the characteristics of fuel pellets (e.g. hydrophobicity and energy density). In current study, torrefaction of furfural residue pellets (FRPs) and sawdust pellets (SPs) was performed by employing tubular reactor furnace, and quality of pellets was compared. The characteristics of both types of pellets were significantly improved with increasing torrefaction temperature from 200 °C to 300 °C and residence time from 15 min to 30 min. The highest lower heating value of 23.78 MJ/kg and energy density ratio (1.27) for torrefied furfural residue pellets (TFRPs) and 26.76 MJ/kg and 1.46 for torrefied sawdust pellets (TSPs) were achieved at 300 °C and 120 min. Increasing torrefaction temperature and residence time, the volumetric energy densities of TFRPs increased from 25.69 (at 200 °C and 15 min) to 27.59 kJ/m3 (at 300 °C and 120 min), while those of TSPs correspondingly decreased from 20.81 to 16.69 kJ/m3. The highest true densities (i.e. 2.40 and 1.85 g/cm3) and porosities (i.e. 52 and 65 v %) of TFRPs and TSPs were achieved at 300 °C and 120 min, much higher than those of un-torrefied pellets. Moisture uptake of TFRPs and TSPs at 300 °C were only 1.4 wt% and 2.0-2.8 wt%, respectively, showing strong water-resistant ability. The crystallinity of cellulose in FRPs was found higher than that of SPs, while the crystallinity of cellulose in TFRPs was found lower than that of TSPs at same process conditions. FTIR showed that O-H bond was destroyed after torrefaction for both FRP and SP.

Comparative study for fluidized bed pyrolysis of textile dyeing sludge and municipal sewage sludge.

A comparative research was performed to evaluate the products yields and chars properties for pyrolysis of textile dyeing sludge (TDS) and municipal sewage sludge (MSS). The high fixed carbon (19.36 wt%) and low volatile (23.66 wt%) contents of TDS resulted in higher char yields and lower condensate yields. TDS char (TC) had a higher sulfur (S) retention efficiency than MSS char (MC) and CaO exhibited a great S retention effect in MC. More alkali and alkaline earth metals (e.g. Na, K, Mg and Ca) in MSS contributed to enhanced catalytic pyrolysis. In comparison to non-catalytic pyrolysis, chars from catalytic pyrolysis had lower iodine number and higher methylene blue (MB) adsorption value. MB adsorption values of MC (212.28-414.20 mg/g) were much higher than those of TC (84.32-156.07 mg/g). In contrast, heavy metals risk degrees of MC (4.20-7.56) were lower than those of TC (7.55-12.87), and heavy metals in TC and MC showed slight risks to environment.