Stabilization of heavy metals in solid waste and sludge pyrolysis by intercalation-exfoliation modified vermiculite.

Increasing amounts of solid waste and sludge have created many environmental management problems. Pyrolysis can effectively reduce the volume of solid waste and sludge, but there is still the problem of heavy metal contamination, which limits the application of pyrolysis in environmental management. The intercalated-exfoliated modified vermiculite (IEMV) by intercalators of sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide and octadecyltrimethylammonium bromide were used to control the release of Cd, Cr, Cu, Zn and Pb during pyrolysis process of sludge or solid waste. The retention of heavy metals in sludge was generally better than that in solid waste. The IEMV by octadecyltrimethylammonium bromide as the intercalator calcined 800 °C (STAB-800) was the best additive for heavy metal retention, and the retention of Cr, Cu and Zn was significantly better than that of Pb and Cd. Cr, Cu, Zn and Pb were at low risk, while Cd had considerable risk under certain circumstances. New models were proposed to comprehensively evaluate the results of the risk and forms of heavy metals, and the increasing temperature was beneficial in reducing the hazards of heavy metals by the addition of STAB-800. The reaction mechanism of heavy metals with vermiculite was revealed by simulation of reaction sites, Fukui Function and Frontier Molecular Orbital. Thermal activation-intercalated-exfoliated modified vermiculite (T-IEMV) is more reactive and had more active sites for heavy metals. Mg atoms and outermost O atoms are the main atoms for T-IEMV to react with heavy metals. The Cr, Cu and Zn have better adsorption capacity by T-IEMV than Pb and Cd. This study provides a new insight into managing solid waste and sludge and controlling heavy metal environmental pollution.

Effective stabilization of heavy metals in solid waste and sludge pyrolysis using intercalated-exfoliated modified vermiculite: Experiment and simulation study.

Pyrolysis is effective in reducing the volume of solid waste and sludge, and produces less pollutants than incineration and landfill, but the process still suffers from heavy metal pollution. Four types of intercalated-exfoliated modified vermiculite (UIV, DIV, TIV and 3IV) were prepared using urea, dimethylsulfoxide, tributyl phosphate and 3-aminopropyltriethoxysilane as intercalators for the control of Cd, Cr, Cu, Pb and Zn in municipal sewage sludge (MSL), paper mill sludge (PML), municipal domestic waste (MWA) and aged refuse (AFE). The larger the interlayer spacing of the vermiculite, the more favorable the retention of heavy metals. 3IV was the most effective additive, with an average retention of more than 75 % of all heavy metals at 450 ℃ for the four raw materials. Cr, Cu, Pb and Zn were all at low potential ecological risk (Pr), while Cd was moderate or considerable Pr, and the addition of 3IV reduced the Pr. Distribution of intercalators between vermiculite interlayers was haphazard, and interlayer spacing results were close to those of the experiment (except for tributyl phosphate). The reactive electrons mainly flowed from the Highest Occupied Molecular Orbital (HOMO) of vermiculite flakes to the Lower Unoccupied Molecular Orbital (LUMO) of heavy metal chlorides. In contrast, the reactive electrons mostly flowed from the HOMO of heavy metal oxides to the LUMO of vermiculite flakes. Heavy metal oxides were more readily adsorbed on vermiculite flakes than heavy metal chlorides, and the adsorption capacity of Cr and Zn was stronger than that of Cd, Pb and Cu.

Influence of silica-aluminum materials on heavy metals release during paper sludge pyrolysis: Experimental and theoretical studies.

It is of great significance to reduce the secondary risk of heavy metals during the pyrolysis of paper sludge. This study used kaolin and alumina-silica-based xerogels to control heavy metals released during sludge pyrolysis. Pyrolyzing a mixture of sludge and 7% kaolin at 400 °C achieved high retention rates for Cu (95.85%), Zn (95.97%), Pb (97.15%), Cd (84.23%), and Cr (84.05%) when the pyrolysis tail gas was treated with 9 g of xerogel. The addition of kaolin facilitated the transformation of Cu, Zn, Pb, and Cr from the unstable fraction to the stable fraction in pyrolysis biochar, reducing their leachability. The xerogels also played a crucial role in adsorbing and stabilizing the heavy metals. The results of thermodynamic equilibrium calculations showed that Pb(g), PbS(g), PbCl2(g), PbCl(g), Zn(g), ZnCl2(g), and Cd(g) were the main gaseous products of Zn, Pb, and Cd during paper sludge pyrolysis. The Pb atoms in PbCl2 and PbS, and the Zn atoms in ZnCl2 bond with the oxygen atoms on the kaolin surface by covalent bonds, while the Cl atoms in PbCl and the Pb atoms of elemental lead form ionic bonds with H and O atoms on the kaolinite surface, respectively. These experimental and simulation results offer new ideas for controlling heavy metals during sludge pyrolysis.

Experiment and mechanism study on enrichment of heavy metals during MSW pyrolysis by modified kaolin.

Experiment and mechanism studies on the enrichment of Pb, Cd, Zn, As, and Cr by modified kaolin were investigated during MSW (municipal solid waste) pyrolysis at 450 ~ 650 °C. The results showed that γAlOK(micro- and nano-γAl2O3 by hydrothermal method modified kaolin) was relatively selective for the solid phase enrichment of Cr and As, while CaHPK (CaHPO4 impregnated modified kaolinite) was more advantageous for the adsorption of Pb and Zn, which might be related to the thermal stability of γAl2O3 and the thermal conversion of CaHPO4. Compared with the original kaolin, the adsorption and retention capacity of γAlOK for As was improved by 20 ~ 30%. Moreover, the retention rate of modified kaolin for Cd decreased from 66.75 to 30.30% at 450 ~ 650 ℃, and the effect of temperature on the volatilization of Cd was always greater than the active components on the surface of modified kaolin. In the fluidized bed experiment, the physical mixing of different modified kaolin achieves complementary advantages on the retention capacity of heavy metals. In addition, the ∆E between Ca2P2O7 and PbCl2 is smaller than that of γAl2O3 at 500 ~ 650 °C, i.e., their electron transfer induction is stronger, and therefore more favorable for electron transfer and stable chemical bond formation.

Efficient with low-cost removal and adsorption mechanisms of norfloxacin, ciprofloxacin and ofloxacin on modified thermal kaolin: experimental and theoretical studies.

Quinolone antibiotics (QNs) can be potential hazard to environment and human. Combination of experimental and theoretical studies was used to analyze the adsorption properties of norfloxacin, ciprofloxacin and ofloxacin on modified thermally activated kaolin (KL). Main factors (calcination temperature, dose, pH, cations and regeneration) affecting the adsorption were discussed. Adsorption processes fit the pseudo-second order kinetic and Langmuir model well. The adsorption removal of norfloxacin, ciprofloxacin and ofloxacin can reach 88.53%, 89.43% and 91.46%, respectively. Cations inhibited adsorption, and AlS-KLB can maintain 80% efficiency in five cycles under optimal conditions. Simulations showed that the materials had good adsorption capacity for QNs, and the "①" of KL had the best capacity. Simulations explain the adsorption mechanism: F, H, O atoms of QNs are covalently bonded to O atoms from KL, Al2O3 and Al (OH)3, C atoms from amorphous carbon and H atoms from C-H and Al (OH)3. The Al atoms of Al2O3 and Al, Si atoms of KL are ionically bonded to F, H, O atoms of QNs. This study shed new light on the removal of QNs by providing low-cost and efficient modified KL and elucidating the adsorption mechanism in conjunction with DFT simulations.

[Three-dimensional printing combined with distal humeral osteotomy for cubital varus deformity in children].

OBJECTIVE: To explore clinical effect of three-dimensional(3D) printing combined with distal humerus osteotomy for children with cubital varus deformity. METHODS: From January 2017 to January 2020, 17 cubital varus deformity children treated with distal humerus osteotomy were retrospective analysis, included 11 boys and 6 girls, aged from 5 to 11 years old with an average of (7.8±1.7) years old. A model of affected side elbow joint was made by 3D printing technique before operation, pre-operation was performed on the model. Three-dimensional model was successfully used for distal humeral osteotomy during operation. Carrying angle, flexion and extension angle of elbow joint were compared before and six months after operation, and Flynn scoring criteria was used to evaluate clinical effect. RESULTS: All children were followed up for 6 to 12 months with an avergae of (9.6±1.7) months. One child occurred wound infection and healed completely after dressing change. No complications such as nonunion, internal fixation and nerve injury occurred. Carrying angle of affected limb was improved from (-20.8±2.4)°before operation to (7.2±2.3)°at 6 months after operation (P<0.01). Angle of affected elbow joint extension improved from (-5.6±3.9)° before opeation to(-2.6±2.1)°at 6 months after operation (P<0.01). There was no significant difference in extension angle of elbow joint between preopertaion and postopertaion at 6 months (P>0.05). While there was no difference in elbow joint function on the healthy side and affected side at 6 months after opertaion (P>0.05). According to Flynn scoring criteria, 13 patients got excllent results and 4 moderate. CONCLUSION: Three-dimensional printing combined with distal humerus osteotomy in treating elbow varus deformity could receive satisfactory clinical effect, which could accurately assist correction of cubital varus deformity, restore physiological structure and function of elbow joint.

Environmental impact comparison of wheat straw fast pyrolysis systems with different hydrogen production processes based on life cycle assessment.

This study aimed to evaluate the environmental impact of 1000 kg h-1 wheat straw to produce biofuel via fast pyrolysis with three different hydrogen production processes by the life cycle assessment (LCA) based on Chinese Life Cycle Database (CLCD). The primary energy depletion (PED), global warming potential (GWP), abiotic depletion potential (ADP) and respiratory inorganics (RI) impact categories of 1 MJ biofuel produced were employed for comparison. In case 1, the hydrogen was derived from natural gas steam reforming, and all the bio-oil was hydrotreated to produce the biofuel. In case 2, a part of the aqueous phase was reformed to produce hydrogen, whereas the remaining bio-oil was hydrotreated to produce biofuel. In case 3, all the aqueous phase of bio-oil was reformed to produce hydrogen, a part of hydrogen generated by reforming was used to oil phase hydrotreated and the excess hydrogen was considered as a co-product. Our results show that the PED, GWP, ADP and RI of case 3 are 0.1355 MJ, -17.96 g CO2eq., 0.0338 g antimonyeq and 0.0461 g PM2.5eq.. Compared with conventional diesel, the PED, GWP, ADP and RI of case 3 were reduced by 89.81, 117.44, 1.74 and 85.03%, respectively. The results of sub-process contribution analysis and sensitivity analysis suggested that the electricity consumption for the bio-oil production has the maximal effect on the total PED, GWP and RI of case 3, whereas the amount of fertilizers in the biomass production sub-process has the maximal effect on the total ADP.

The adsorption mechanism of heavy metals from coal combustion by modified kaolin: Experimental and theoretical studies.

Experimental and theoretical studies are combined to analyze the adsorption properties of modified kaolin for heavy metal (Pb, Cd, Zn and Cr) from coal combustion. The results indicate that the retention effect of kaolin for Pb, Cd, Zn and Cr has been significantly enhanced after intercalation-exfoliation combined with acid/alkali modification, which is mainly attributed to more active sites for adsorption, richer porosity and more effective in retarding coking of coal ash. The higher oxygen concentration is positive to the enrichment of heavy metals at 900-1200 â„ƒ, while the coking of coal ash and the thermal conversion of additives become the main factors affecting the absorption at 1200-1300 â„ƒ. The acid/alkali modification effectively promotes the inductive effect of electron transfer between modified kaolin and heavy metals to form stable chemical adsorption. The electron transfer induction of modified kaolin for Pb, Cd is higher than Zn, Cr at 900-1000 â„ƒ, while the adsorption activity of mullite and cristobalite for Zn, Cr is stronger than Pb, Cd at 1200-1300 â„ƒ. In addition, Pb, Cd and Zn are more readily adsorbed as oxides by additives at 900-1300 °C. The results shed new light on strengthening the adsorption activity of kaolin to Pb, Cd, Zn and Cr in high temperature.

Comparative study on intercalation-exfoliation and thermal activation modified kaolin for heavy metals immobilization during high-organic solid waste pyrolysis.

With the new municipal solid waste classification policy implemented in China, attention on achieving the waste-to-energy disposal of "dry waste" has been growing. Pyrolysis conversion of organic waste into value-added chemicals is a promising method to treat solid waste. However, after removing the non-combustible components of "dry waste", the obtained high-organic solid waste (HSW) contains various heavy metals, which requires urgent attention during thermochemical conversion. To mitigate heavy metals risk, kaolin was employed as additive during HSW pyrolysis, and intercalation-exfoliation and thermal activation modifications were performed on the kaolin to further immobilize and stabilize heavy metals in the derived chars. The characterization results illustrated that the interlayer spacing, pore volume and diameter of kaolin were expanded after intercalation-exfoliation modification, providing more opportunities for the adsorption of metals. The thermal activation method favored the transformation of kaolin into metakaolin via dehydroxylation to enhance its nonhexacoordinated Al proportion and chemisorption. During 450-650 °C, kaolin exhibited an effective solid enrichment performance for targeting heavy metals, and the intercalation-exfoliation and thermal activation modification further enhanced the adsorption capacity of the kaolin for Cd, Cr, Pb and Cr, Cu, Pb, Zn, respectively. Compared with Cu and Zn, additives demonstrated better stabilization effects for Cd, Pb, and Cr, transforming more bioavailable fractions to the residual speciation. Overall, a higher pyrolytic temperature (650 °C) and the addition of effective additives could simultaneously increase the residual fraction and decrease the bioavailable fraction of heavy metals in HSW-derived chars, reducing the potential ecological risk.

Theoretical study on the adsorption mechanism of PbCl2/CdCl2 by kaolinite during municipal solid waste pyrolysis.

In the process of municipal solid waste (MSW) pyrolysis, kaolinite possesses an outstanding trapping effect on semi-volatile metal vapors (Pb, Cd) through physical and chemical adsorption. In this paper, the microscopic mechanism of PbCl2 and CdCl2 adsorption on the surface of Al rings and Si rings of kaolinite was investigated by combining Monte Carlo method with density functional theory (DFT). The calculations indicate that the continuously enriched pore structure in the process of dehydroxylation indirectly influences the adsorption of PbCl2/CdCl2 by kaolinite. Under the non-bond interaction and electron transfer induction, PbCl2 molecules are more conveniently adsorbed on the Al-(001) surface than CdCl2, while the adsorption sites of CdCl2 molecules are more widely distributed on the Si-(001) surface. Moreover, the transform in the Al-coordination and the exposed active oxygen atoms significantly affect the adsorption activity of kaolinite (the capability to gain and lose electrons). Considering the energy barrier and electrophilic nucleophilic sensitivity, it is more feasible for PbCl2/CdCl2 to be adsorbed near IV/V-coordinated Al and active O under Van der Waals action. Subsequently, IV/V-coordinated Al will act as an electron acceptor, and the active oxygen atoms after dehydrogenation will serve as an electron donor. Under the induction of the energy difference of frontier orbitals, the electrons transfer will encourage the formation of more stable adsorption states. The results shed new light on strengthening the adsorption activity of kaolinite to PbCl2/CdCl2 in the process of MSW pyrolysis.

Microwave-assisted catalytic fast pyrolysis of rice husk over a hierarchical HZSM-5/MCM-41 catalyst prepared by organic base alkaline solutions.

This paper reports the results obtained for microwave-assisted catalytic fast pyrolysis (MACFP) of rice husk. The MACFP process employed a hierarchical catalyst prepared via a combination of organic alkali treatment (TPAOH) and the generation of an external layer of MCM-41-type mesoporous channels. We propose this catalyst which is used for the first time for pyrolysis of lignocellulosic biomass, as a tool to reduce coke agglomeration and increase hydrocarbon yields. Our results indicate that during catalyst preparation the mass fraction of cetyltrimethylammonium bromide (CTAB) has a direct effect on the content of MCM-41 formed on top of the HZSM-5 core. For MACFP, we hypothesize that the small molecules generated from thermal decomposition of rice husk react further to form aromatic and aliphatic hydrocarbons by decarbonylation, decarboxylation, oligomerization and aromatization. The highest hydrocarbon yield (60.5%) was obtained for a catalyst modified by a 2.0 mol/L TPAOH solution, with 10 wt% of CTAB (template for producing MCM-41), as well as with digestion and crystallization at 110 °C for 24 h. In addition, the highest liquid yield (47.6 wt%) was obtained at 550 °C. The relative content of hydrocarbons goes through a maximum of 60.5% with CTAB mass fraction which was higher than values obtained with MCM-41 (3.2%) and HZSM-5 (36.0%). Characterization and catalytic testing results suggest that the digestion temperature plays a more important role in the catalyst synthesis than the crystallization temperature. High digestion temperature (120 °C) decreases the overall hydrocarbon selectivity from 60.5% (110 °C) to 39.2%. The relative content of oxygenates reached the lowest value of 35.9% at the digestion and crystallization temperature of 110 °C. The synergistic effect of the MCM-41 shell and the HZSM-5 core promotes the catalytic activity, leading to outstanding deoxygenation capabilities and excellent selectivity to BTEX (52.7%).

Comparison of Laminoplasty vs. Laminectomy for Cervical Spondylotic Myelopathy: A Systematic Review and Meta-Analysis.

OBJECTIVES: Laminoplasty (LP) and laminectomy (LC) with or without fusion are recommended as treatment procedures for cervical spondylotic myelopathy (CSM). The purpose of this study is to conduct a meta-analysis to analyze the results of CSM patients undergoing LP or LC surgery. METHODS: We systematically and comprehensively searched Web of Science, Cochrane Library, PubMed, EMBASE, OVID, VIP database, Google Scholar, Chinese Bio-medicine Literature database, and China Scientific Journal Full-text database to July 2021 for randomized controlled trials (RCTs) and observational case series that compared LP and LC in patients with CSM. The main endpoints were the surgical process, radiographic outcomes, clinical outcomes, and surgical complications. RESULTS: A total of 19 were included the inclusion criteria in this meta-analysis (n = 4,348 patients). There was no significant difference in range of motion (ROM), sagittal vertical axis (SVA), Japanese Orthopedic Association (JOA), Cobb angle, visual analog scale (VAS), cervical curvature index (CCI), Nurick score, Neck Dysfunction Index (NDI), and complications. LP was found to be superior than LC in terms of complications of C5 radiculopathy and surperficial infection. CONCLUSION: Our results indicate that LP can achieve better results in C5 radiculopathy and superficial infection in surgical treatment of CSM compared with LC. Further high-quality research is warranted to further verify our findings. SYSTEMATIC REVIEW REGISTRATION: PRISMA: CRD42018107070.

[Nomograma prediction of the surgical treatment in triad of elbow].

OBJECTIVE: To establish an individualized Nomogram prediction model for predicting the postoperative recovery of patients with triad of elbow (TE) by analyzing risk factors of triad of elbow joint. METHODS: From January 2012 to December 2018, 116 patients with TE who met the criteria were collected. The independent risk factors were screened by univariate Logistic regression analysis. The statistically significant risk factors were included in the multivariate Logistic regression model. The R software was used to establish the Nomogram diagram model to predict the postoperative recovery of TE patients. C index was used to verify the discrimination, Calibration plot of the model, and the decision curve (decision curve analysis, DCA) to verify the net clinical benefit rate of the model. RESULTS: Forty-four of the 116 patients with TE developed symptoms after operation, with an incidence of 37.93%. Age (OR=1.930, 95% CI 1.418 to 2.764), work (OR=6.153, 95%CI 1.466 to 31.362), smoking(OR=4.463, 95%CI 1.041 to 2.291), the Mason of radial head(OR=1.348, 95%CI 2.309 to 9.348), the Regan-Morrey of coronal process (OR=4.424, 95%CI 1.751 to 2.426) and postoperative elbow immobilization time(OR=7.665, 95%CI 1.056 to 5.100) were independent risk factors for postoperative recovery of TE (P<0.05). The C-index of Nomogram plot was 0.716. Calibration plot showed that the predictive model was consistent, and the DCA curve showed satisfactory clinical net benefit. CONCLUSION: The Nomogram for predicting postoperative results of TE patients based on six independent risk factors:age, work, smoking, Mason classification of radial head, Regan-Morrey classification of coronal process and immobilization time of elbow joint after operation, has good distinguishing capacity and consistency. Thepredictive model could help clinicians to identify high risk population and establish appropriate intervention strategies.

[Measurement of femoral neck anteversion of developmental dislocation of hip in children by 3D printing technique].

OBJECTIVE: To explore the method and accuracy of measuring the femoral neck anteversion in children with developmental dislocation of the hip by using 3D printing technology, so as to find out the method of measuring the femoral neck anteversion accurately and guide the formulation of the operation plan. METHODS: From June 2016 to September 2018, 17 patients with unilateral developmental dislocation of the hip were enrolled in the study, including 2 males and 15 females, aged 2 to 13 (5.47±0.81) years old, 11 on the left and 6 on the right. The methods of CT, 3D printing and intraoperative anteversion of femoral neck were used to measure the anteversion of femoral neck respectively. The intraoperative measurement was used as the standard reference value forstatistical analysis, and the accuracy of the first two methods was compared. RESULTS: The average value of CT was (36.00±1.66)°, the average value of model method was(43.91±1.62)°, and the average value of intraoperative method was(44.21±1.62)°. There were significant differences in CT measurement, model measurement and intraoperative measurement(P<0.05). There was no significant difference between model method and intraoperative method (P>0.05). CONCLUSION: Compared with the traditional CT method, the 3D printing model method is simpler, more accurate and more repeatable, and can simulate the operation before operation. It is an ideal method to measure the femoral neck anteversion.

Promoting Aromatic Hydrocarbon Formation via Catalytic Pyrolysis of Polycarbonate Wastes over Fe- and Ce-Loaded Aluminum Oxide Catalysts.

Converting polycarbonate (PC) plastic waste into value-added chemicals and/or fuel additives by catalytic pyrolysis is a promising approach to dispose of solid wastes. In this study, a series of Fe-Ce@Al2O3 metal oxides were prepared by coprecipitation, impregnation, and a direct mixing method. The synthesized catalysts were then employed to investigate the catalytic conversion of PC wastes to produce aromatic hydrocarbons. Experimental results indicated that Fe-Ce@Al2O3 prepared by coprecipitation possessed superior catalytic activity because of its high content of weak acid sites, large pore volume, high surface area, and well dispersion of Fe and Ce active species, leading to an ∼3-fold increase in targeted monocyclic aromatic hydrocarbons compared to that achieved noncatalytically. Moreover, an increase in the catalyst to feedstock (C/F) mass ratio was beneficial to the production of aromatic hydrocarbons at the expense of phenolic products, and elevating the C/F ratio from 1:1 to 3:1 considerably increased the benzene formation as the enhancement factor was increased from 2.3 to 8.8.

Comparative study on pyrolysis of bamboo in microwave pyrolysis-reforming reaction by binary compound impregnation and chemical liquid deposition modified HZSM-5.

The deactivation of catalyst is a significant reason for its limited application during the catalytic fast pyrolysis (CFP) process. To reduce the coke formation, binary compound impregnation (BCI) and chemical liquid deposition (CLD) were used to modify HZSM-5 catalysts. At the same time, the self-designed microwave reactor separated the pyrolysis of bamboo and catalytic upgrading of primary vapor, which made the catalytic effect more thorough. Experimental results indicated that CLD used TiO2 deposition to cover external acid sites, while BCI by phosphorus-nickel could cover and partly destroy superficial acid sites through two different ways. Within the scope of the loaded amount studied, the yield of aromatic hydrocarbons in the oil phase increased at first and then decreased, while the coke formation reduced continuously. BTX (benzene, toluene and xylene), the most valuable product in bio-oil, drastically increased by 39.1% and 22.6% respectively over the CLD and BCI modified catalysts. Considering the catalytic performance as well as cost, CLD over HZSM-5 has more advantages in the CFP process to upgrade bio-oil.

Converting polycarbonate and polystyrene plastic wastes intoaromatic hydrocarbons via catalytic fast co-pyrolysis.

Thermochemical conversion of plastic wastes is a promising approach to produce alternative energy-based fuels. Herein, we conducted catalytic fast co-pyrolysis of polycarbonate (PC) and polystyrene (PS) to generate aromatic hydrocarbons using HZSM-5 (Zeolite Socony Mobil-5, hydrogen, Aluminosilicate) as a catalyst. The results indicated that employing HZSM-5 in the catalytic conversion of PC facilitated the synthesis of aromatic hydrocarbons in comparison to the non-catalytic run. A competitive reaction between aromatic hydrocarbons and aromatic oxygenates was observed within the studied temperature region, and catalytic degradation temperature of 700 °C maximized the competing reaction towards the formation of targeted aromatic hydrocarbons at the expense of phenolic products. Catalyst type also played a vital role in the catalytic decomposition of PC wastes, and HZSM-5 with different Si/Al molar ratios produced more aromatic hydrocarbons than HY (Zeolite Y, hydrogen, Faujasite). Regarding the effect of Si/Al molar ration in HZSM-5 on the distribution of monocyclic aromatic hydrocarbons (MAHs), a Si/Al molar ratio of 38 maximized benzene formation with an advanced factor of 5.1. Catalytic fast co-pyrolysis of PC with hydrogen-rich plastic wastes including polypropylene (PP), polyethylene (PE), and polystyrene (PS) favored the production of MAHs, and PS was the most effective hydrogen donor with a ∼2.5-fold increase. The additive effect of MAHs increased at first and then decreased when the PC percentage was elevated from 30 % to 90 %, achieving the maximum value of 32.4 % at 70 % PC.

Experimental study on enrichment of heavy metals by intercalation-exfoliation modified kaolin during coal combustion.

An intercalation-exfoliation method is applied to modify the natural kaolin mineral, so that to improve the enrichment effects on heavy metals (Zn, Pb, Cr & Cd) during coal combustion. The modified kaolin is scanned by electron microscope (SEM), X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and Brunner-Emmett-Teller (BET), which indicate that the natural kaolin is peeled off to form fine flakes and the interlayer spacing is significantly increased. The coal-kaolin combustion tests were performed in a tube furnace from 900°C to 1300°C. It is found that the enrichment of heavy metals is enhanced obviously during the coal combustion, especially when the raw kaolin has high activity. Besides, the adsorption effects on the above four heavy metals are different. To be specific, the kaolin modified by potassium acetate has a better performance for Zn and Pb, but that intercalated by dimethyl sulfoxide shows better influences on Cd and Cr. The modified kaolin can provide more active sites for the adsorption of heavy metals, enhance chemical adsorption, and fix heavy metals in the form of aluminosilicates, silicates and aluminates. These founding could reduce the pollutant emissions of coal combustion in industrial applications.

Catalytic fast co-pyrolysis of waste greenhouse plastic films and rice husk using hierarchical micro-mesoporous composite molecular sieve.

Catalytic fast co-pyrolysis of waste greenhouse plastic films and rice husk over a hierarchical HZSM-5/MCM-41 catalyst was performed in an analytical Py-GC/MS. We evaluated the effect of pyrolysis temperature and the ratio of rice husk to waste greenhouse plastic films on the total peak area of condensable organic products and CO2. In order to evaluate synergy possibilities among the two feedstocks, we performed non-catalytic pyrolysis and catalytic fast pyrolysis of rice husk and waste greenhouse plastic films separately. In addition, we report results for the catalytic fast co-pyrolysis of the mixture rice husk and waste greenhouse plastic films. The maximum relative content of hydrocarbons from catalytic fast co-pyrolysis of rice husk and waste greenhouse plastic films is obtained at 600 °C. When the mass ratio of rice husk to waste greenhouse plastic films is 1:1.5, the relative content of hydrocarbons reaches a maximum (71.1%). The hierarchical micro-mesoporous composite molecular sieve used in this work has outstanding catalytic activity and increases the relative content of hydrocarbons.

Investigation on gaseous pollutants emissions during co-combustion of coal and wheat straw in a fluidized bed combustor.

Co-combustion of coal and wheat straw (WS) was conducted in a lab-scale BFB combustor. Fuel composition (coal, 70%coal+30%WS), temperature (750, 800, 850, 900, 950 °C), secondary air ratio (0, 10%, 20%, 30%) were varied to on the release of gaseous pollutant was studied. CO, NOx and SO2 concentration in flue gas (FG) were measured on-line by a flue gas analyzer. Fly ash (FA), bottom slag (BS) and bed material (BM) were collected, digested and analyzed by ICP-OES to determine the distribution of heavy metals (e.g. Pb, Zn, Cr and Cd). Results indicated that co-combustion could improve the combustion of coal alone by reducing CO, NOx and SO2 emission and carbon content in fly ash effectively. In co-combustion the increasing secondary air could reduce CO emission and SO2 by enhancing disturbance and promoting sulfation respectively while the minimum NO emission was reached at the ratio of 20%. Co-combustion restrained the release of Zn, Cd and Pb compared with coal combustion alone. In co-combustion, high temperature increased their portion in the flue gas. For Zn, Pb and Cd, their content in the bottom solids increased while the portion of Cr decreased. Secondary air decreased their content in fly ash and transferred into flue gas significantly and in bottom solids content of Zn and Pb decreased while Cd increased.