Effect of type of activating agent on properties of activated carbon prepared from digested solid waste.

Anaerobic digestion has been proved to be a widely used and effective technology. The main challenge for the sustainable biogas industry is to find ways to efficiently recycle and utilize the anaerobic digestate. The conversion of digestion products into activated carbon seems to be an attractive way. Therefore, the present study focused on assessing the potential of digested solids as a promising source of activated carbon using a range of activators including KOH, ZnCl2 and H3PO4. The activated carbon prepared from digested solids was subjected to an activation process to investigate the physicochemical and surface properties of the resulting activated carbon. The results showed that KOH appeared to be the best activator for producing activated carbon from high silica precursors such as digested solids. The effectiveness of KOH activation can be attributed to the ability of K to readily form poorly layered compounds with carbon, as well as a significant increase in the number of porosities during KOH activation due to the violent reaction of KOH with C and the volatilization of the inorganic minerals in the digested char. The KOH activated sample had the lowest La and Lc, which means it had the theoretically largest specific surface area. This study provides experimental basis and theoretical guidance for the conversion of digested solids into high value-added activated carbon.

Performance of volatile fatty acids production from food waste at the presence of alkyl ethoxy polyglycosides and sodium dodecyl sulfate.

In the current context of technological and industrial development, strategies for sustainable development and resource utilization have become increasingly important. FW anaerobic fermentation (Fermentation of Wastes) is a process that utilizes organic waste for biotransformation and is widely used for the production of volatile fatty acids (VFAs). Volatile fatty acids (VFAs) are a kind of high value-added product generated from anaerobic fermentation process, and has extensive applications in chemical synthesis and electricity generation. This study investigated the performance of VFAs production from food waste at the presence of alkyl ethoxy polyglycosides (AEG) and sodium dodecyl sulfate (SDS). The highest yield of VFAs was obtained at 0.1 g AEG/g TS (14.53 g COD/L), which increased by 25.80% than the Blank. But inhibited phenomenon was observed at other reactors with relatively low yield and delayed fermentation time. The inhibition of lactate's production and bioconversion delayed the fermentation time, and SDS has changed the acidogenic fermentation type from lactate-butyrate fermentation to acetate fermentation. In addition, more organic matter dissolved in the fermentation liquor with the addition of AEG and SDS, but the hydrolysis and acidification of polysaccharide were inhibited to some extent. Microbial community analysis showed that the abundance of key bacteria Clostridium has significantly decreased from 82.71% (Blank) to 33.54% (AEG) and 23.72% (SDS), leading to low VFAs production performance.

Fermentation broth of food waste: A sustainable electron donor for perchlorate biodegradation.

Microbial reduction has been considered an effective way to remove perchlorate (ClO4-), during which, additional electron donors and carbon sources are required. This work aims to study the potential of fermentation broth of food waste (FBFW) serving as an electron donor for ClO4- biodegradation, and further investigates the variance of the microbial community. The results showed that FBFW without anaerobic inoculum at 96 h (F-96) exhibited the highest ClO4- removal rate of 127.09 mg/L/d, attributed to higher acetate and lower ammonium contents in the F-96 system. In a 5 L continuous stirred-tank reactor (CSTR), with a 217.39 g/m3·d ClO4- loading rate, 100% removal efficiency of ClO4- was achieved, indicating that the application of FBFW in the CSTR showed satisfactory performance for ClO4- degradation. Moreover, the microbial community analysis revealed that Proteobacteria and Dechloromonas contributed positively to ClO4- degradation. Therefore, this study provided a novel approach for the recovery and utilization of food waste, by employing it as a cost-effective electron donor for ClO4- biodegradation.

Integration of hydrothermal and pyrolysis for oily sludge treatment: A novel collaborative process.

In this study, hydrothermal treatment and in situ pyrolysis were combined to develop a novel collaborative process (HCP treatment method). In a self-designed reactor, the HCP method was used to study the influences of hydrothermal temperature and pyrolysis temperature on the product distribution of OS. The products from the HCP treatment of OS were compared with that from the traditional pyrolysis. In addition, the energy balance in the different processes of treatment was analyzed. The results showed that compared to the traditional pyrolysis method, the gas products obtained after HCP treatment achieve a higher H2 production. As the hydrothermal temperature raising from 160 to 200 °C, the H2 production showed an increase from 4.14 to 9.83 ml/g. In addition, GC-MS analysis showed that the content of olefins from the HCP treatment oil was increased from 1.92% to 6.01% compared to traditional pyrolysis. Energy consumption analysis showed that only 55.39% energy consumption of traditional pyrolysis is required for treating 1 kg OS by employing the HCP treatment at 500 °C. All results indicated that the HCP treatment is a clean production process of OS with low energy consumption.

Risk Assessment of Heavy Metal Pollution in Farmland Soils at the Northern Foot of the Qinling Mountains, China.

To provide scientific basis for the prevention and control of heavy metal pollution, a field investigation, sample collection and analysis of the heavy metal content in farmland soils at the northern foot of the Qinling Mountains were conducted. Based on the comparative analysis of the single pollution index method, the Nemerow comprehensive pollution index method, the geological accumulation index method, the potential ecological hazard index method, and the geological accumulation index method were used to comprehensively analyze and evaluate the risk of soil heavy metal pollution. The results showed that the heavy metal pollution of farmland soil at the northern foot of the Qinling Mountains was severe, among which Hg and Cr pollution was relatively obvious. Taking the soil screening values of agricultural land as the standard, the quantity of element Hg in agricultural soils at the northern foot of the Qinling Mountains was higher than the relevant screening value. In the two sample sites investigated, the intensity of the heavy metal accumulation index in Baoqizhai Village was Hg > Cr > Cu > As > Pb, and in Dayangyu Village it was Cr > Cu > As > Pb. Among them, in Baoqizhai Village it shows the heavy pollution caused by Hg (Igeo= 3.42) and the light pollution caused by Cr (Igeo < 1) in the two areas. Hg is mostly affected by mining activities and its atmospheric subsidence. At the same time, Cr is mainly derived from the weathering of rock parent material and is also affected by anthropogenic factors to a certain extent. The accumulation of heavy metals in the farmland soil around the northern foot of the Qinling Mountains was relatively high, posing a threat to the surrounding soil environment. Therefore, it is urgent to control farmland soil environmental pollution.

Characterization of heavy metals and oil components in the products of oily sludge after hydrothermal treatment.

In this study, the method combining hydrothermal treatment (HT) and in-situ mechanical compression (MC) is used to treat oily sludge. The possible transfer and reaction pathways of different oil components during the process of HT&MC were investigated. In addition, the leaching toxicity, distribution, and risk of heavy metals in oily sludge treated in different temperatures and residence times were evaluated. The results revealed that siloxane and heavy oil components are left in the solid residue, and the light oils and oils with hydrophilic groups are transferred to hydrothermal fluids. The content of Cd, Cr, Pb, and Zn in form of F4 (residual) in the solid residue obtained at a hydrothermal temperature of 240 °C and residence time of 60 min increased by 7.37%, 1.21%, 3.06%, and 9.97%. This reduced the biological availability and environmental risk of heavy metals in the treated oily sludge. Meanwhile, the result of FT-IR illustrated an increase in hydroxyl groups of alcohols, phenols and organic acids, which have a beneficial effect on the adsorption of heavy metals and other pollutants. All results indicated that HT&MC might be a suitable pretreatment method for the stabilization of heavy metals in oily sludge.

Critical assessment of plasma tar reforming during biomass gasification: A review on advancement in plasma technology.

The contamination of producer gas with tar due to inefficient removal methods remains a major challenge in the bioenergy industry and a critical barrier, hindering commercial applications of biomass gasification technology. Single syngas treatment through primary and secondary tar removal method is insufficient to produce a tar free syngas. Currently widely applied tar removal methods are catalytic reforming and plasma reforming. Though both methods have hindrances of fast catalyst deactivation due to coke deposition and reduced syngas selectivity with large quantities of undesired liquid products from plasma reforming. Our review paper showed that hybrid plasma catalysis could be a breakthrough in tar reforming methods and overcome major drawbacks. Though, very little work on review articles have reported merging non-thermal plasma and heterogeneous catalyst. Plasma catalysis offers an inexpensive viable future technology of tar reforming through biomass gasification. The article assessed in-depth the synergistic effect created during the interaction of energetic plasma species and catalyst radicals in tar reforming. Review results show that merging plasma with catalysts noticeably Nickel, Non-nickel metal catalyst and zeolites gave pleasant results of tar conversion efficiency, improved gas selectivity and improved catalyst stability.

Co-pyrolysis of biomass and waste tires under high-pressure two-stage fixed bed reactor.

The distribution of biomass pyrolysis products under high pressure have rarely been reported. In this study, the effect of pressure on the product distribution of pine sawdust (PS) pyrolysis was studied. The synergistic effect of the side wall rubber (SWR) and PS was confirmed under pressurized conditions. Calcined bottom ash (CBA) and SWR char (SWRC) were used to enhance the quality of the pressurized co-pyrolysis products. The PS and SWR pyrolysis chars obtained under high pressure conditions exhibited serious melting and cross-linking problem. The CO2 content decreased to 19.96 vol% in co-pyrolysis gas with the CBA/SWRC7/3 catalyst. The water content decreased by 85.71% after the SWRC catalyst in the pressurized co-pyrolysis process. Compared with the concentration of benzene in PS and SWR oil, the concentration of benzene in SWR/PS7/3 oil without catalysts increased by 9.57 times and 0.25 times, respectively.

Hydrothermal treatment combined with in-situ mechanical compression for floated oily sludge dewatering.

Due to the high moisture content of the oily sludge, the conventional use of oily sludge treatment presents poor feasibility in industrial applications. Hence, finding an efficient and energy-saving technology is still an urgent need for the dewatering of oily sludge. In this paper, an innovative method combining hydrothermal treatment (HT) and in-situ mechanical compression (MC) for dewatering of floated oily sludge (FOS) was proposed. Series of experiments on HT&MC were conducted to verify the method. 77-96 wt% of water can directly be separated from FOS by the HT&MC treatment under the temperature of 120-240 °C and residence times of 10-60 min. The bound water content in raw and HT&MT treated FOS were measured by employing the differential scanning calorimetry (DSC) to evaluate the dewatering ability. The result of DSC illustrates the freezing peaks shifted from -11.1 °C to -21.2 °C as the diameter of water droplets reduced. Meanwhile, the comprehensive characterization analysis of products, including chemical oxygen demand (COD), NH4+-N, and gas chromatograph (GC) were conducted. All results indicated that HT&MC is advisable for dewatering of oily sludge.

Copyrolysis of Biomass and Coal: A Review of Effects of Copyrolysis Parameters, Product Properties, and Synergistic Mechanisms.

Concerns in the last few decades regarding the environmental and socioeconomic impacts of the dependence on fossil fuels have resulted in calls for more renewable and alternative energy sources. This has led to recent interest in copyrolysis of biomass and coal. Numerous reviews have been found related to individual pyrolysis of coal and biomass. This review deals mainly with the copyrolysis of coal and biomass and then compares their results with those obtained using coal and biomass pyrolysis in detail. It is controversial whether there are synergistic or additive behaviours when coal and biomass are blended during copyrolysis. In this review, the effects of reaction parameters such as feedstock types, blending ratio, heating rate, temperature, and reactor types on the occurrence of synergy are discussed. Also, the main properties of the copyrolytic products are pointed out. Some possible synergistic mechanisms are also suggested. Additionally, several outlooks based on studies in the literature are also presented in this paper.

High speed railway environment safety evaluation based on measurement attribute recognition model.

In order to rationally evaluate the high speed railway operation safety level, the environmental safety evaluation index system of high speed railway should be well established by means of analyzing the impact mechanism of severe weather such as raining, thundering, lightning, earthquake, winding, and snowing. In addition to that, the attribute recognition will be identified to determine the similarity between samples and their corresponding attribute classes on the multidimensional space, which is on the basis of the Mahalanobis distance measurement function in terms of Mahalanobis distance with the characteristics of noncorrelation and nondimensionless influence. On top of the assumption, the high speed railway of China environment safety situation will be well elaborated by the suggested methods. The results from the detailed analysis show that the evaluation is basically matched up with the actual situation and could lay a scientific foundation for the high speed railway operation safety.

FeCl3 and acetic acid co-catalyzed hydrolysis of corncob for improving furfural production and lignin removal from residue.

In order to increase furfural yield and lignin removal, both FeCl(3) and acetic acid were used to co-catalyze the hydrolysis of corncob. A series of experiments were carried out to investigate the effects of acetic acid, FeCl(3) concentrations and temperatures on furfural production and residue characteristics. The results showed that high FeCl(3) concentrations caused serious cellulose degradation while acetic acid was more effective for lignin removal. A maximum furfural yield of 67.89% (35.74% higher than that in conventional sulfuric acid-catalyzed process) was obtained at 180°C in the presence of 20mM of FeCl(3) and 3% of acetic acid. Simultaneously, lignin removal reached 54.79%, and 74.29% of the cellulose was remained for further utilization. Acetic acid and FeCl(3) co-catalyzed hydrolysis was not only a high efficiency and environmental friendly technique, but also provided a possibility to utilize the furfural residue for ethanol production and other industries.

Study on characteristics of printed circuit board liberation and its crushed products.

Recycling printed circuit board waste (PCBW) waste is a hot issue of environmental protection and resource recycling. Mechanical and thermo-chemical methods are two traditional recycling processes for PCBW. In the present research, a two-step crushing process combined with a coarse-crushing step and a fine-pulverizing step was adopted, and then the crushed products were classified into seven different fractions with a standard sieve. The liberation situation and particle shape in different size fractions were observed. Properties of different size fractions, such as heating value, thermogravimetric, proximate, ultimate and chemical analysis were determined. The Rosin-Rammler model was applied to analyze the particle size distribution of crushed material. The results indicated that complete liberation of metals from the PCBW was achieved at a size less than 0.59 mm, but the nonmetal particle in the smaller-than-0.15 mm fraction is liable to aggregate. Copper was the most prominent metal in PCBW and mainly enriched in the 0.42-0.25 mm particle size. The Rosin-Rammler equation adequately fit particle size distribution data of crushed PCBW with a correlation coefficient of 0.9810. The results of heating value and proximate analysis revealed that the PCBW had a low heating value and high ash content. The combustion and pyrolysis process of PCBW was different and there was an obvious oxidation peak of Cu in combustion runs.

Synthesis of carbon nanotubes and porous carbons from printed circuit board waste pyrolysis oil.

The possibility and feasibility of using pyrolysis oil from printed circuit board (PCB) waste as a precursor for advanced carbonaceous materials is presented. The PCB waste was first pyrolyzed in a laboratory scale fixed bed reactor at 600 degrees C to prepare pyrolysis oil. The analysis of pyrolysis oil by gas chromatography-mass spectroscopy indicated that it contained a very high proportion of phenol and phenol derivatives. It was then polymerized in formaldehyde solution to synthesize pyrolysis oil-based resin which was used as a precursor to prepare carbon nanotubes (CNTs) and porous carbons. Scanning electron microscopy and transmission microscopy investigation showed that the resulting CNTs had hollow cores with outer diameter of approximately 338 nm and wall thickness of approximately 86 nm and most of them were filled with metal nanoparticles or nanorods. X-ray diffraction reveals that CNTs have an amorphous structure. Nitrogen adsorption isotherm analysis indicated the prepared porous carbons had a Brunauer-Emmett-Teller surface area of 1214 m(2)/g. The mechanism of the formation of the CNTs and porous carbons was discussed.

Research into fine powder and large particle tyre pyrolysis.

This paper investigates the kinetics of the pyrolysis of scrap tyre using thermogravimetry and a small batch laboratory-scale externally heated fixed-bed. Five particle sizes (20-40, 40-60, 60-80, 80-100, 100-200 mesh) and five heating rates (5, 10, 15, 20, 40 K min(-1)) were investigated. The results show that there is no obvious distinction on weight loss for different sizes. With increasing heating rate the weight loss regions shift to a higher temperature range and the weight loss rate increases. The activation energy (E) and pre-exponential factor constant (A) were calculated using the Arrhenius type kinetic model. The heat value of pyrolysis gases is in the range of 12 to 22 MJ Nm(-3). The yields of solid, liquid and gas of pyrolysis scrap tyre and tyre cube at 800 degrees C were investigated, the ratio of pyrolysis production composition of scrap tyre and tyre cube for gas, oil and char is found to be 35 : 23 : 42 and 10 : 31 : 59, respectively.

A novel reforming method for hydrogen production from biomass steam gasification.

In this work, an experimental study of biomass gasification in different operation conditions has been carried out in an updraft gasifier combined with a porous ceramic reformer. The effects of gasifier temperature, steam to biomass ratio (S/B), and reforming temperature on the gas characteristic parameters were investigated with and without porous ceramic filled in reformer. The results indicated that considerable synergistics effects were observed as the porous ceramic was filled in reformer leading to an increase in the hydrogen production. With the increasing gasifier temperature varying from 800 to 950 degrees C, hydrogen yield increased from 49.97 to 79.91 g H(2)/kg biomass. Steam/biomass ratio of 2.05 seemed to be optimal in all steam-gasification runs. The effect of reforming temperature for water-soluble tar produced in porous ceramic reforming was also investigated, and it was found that the conversion ratio of total organic carbon (TOC) contents is between 71.08% and 75.74%.

Thermogravimetric analysis and kinetic study on large particles of printed circuit board wastes.

Pyrolysis of large printed circuit board (PCB) waste particle was conducted on a specially designed laboratory-scale thermobalance (Macro-TG) with sample loading of 30 g under dynamic nitrogen atmosphere. The effects of heating rate (10, 15, 20 and 25 degrees C min(-1)) and particle size (1 mm x 1 mm, 5 mm x 5 mm, 10 mm x 10 mm and 10 mm x 20 mm) were examined. To compare the different decomposition behavior of fine and large one, the thermal decomposition of PCB waste powder (approximately 5mg) was also performed on a thermogravimetric analyzer (common TG) under various heating rates (10, 15, 20 and 40 degrees C min(-1)) and particle size ranges (0.198-0.165 mm, 0.165-0.074 mm, 0.074-0.055 mm and 0.055-0.047mm). Experimental results show that large particle has a pyrolysis reaction retardancy compared to fine one. The distributed activation energy model was used to study the pyrolysis kinetics. It was found that during pyrolysis process, values of frequency factor (k(0)) changed with different activation energy (E) values. On common TG, the E values range from 156.95 to 319.37 kJ mol(-1) and k(0) values range from 2.67 x 10(13) to 2.24 x 10(27)s(-1). While, on Macro-TG, the range of E was 31.48-41.26 kJ mol(-1) and of the frequency factor was 19.80-202.67s(-1).