Bisolute Sorption and Thermodynamic Behavior of Organic Pollutants to Biomass-derived Biochars at Two Pyrolytic Temperatures
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The bisolute sorption and thermodynamic behavior of organic pollutants on low temperature biochars (LTB) at 300 °C and high temperature biochars (HTB) at 700 °C were determined to elucidate sorptive properties of biochar changed with pyrolytic temperatures. The structural characteristics and isotherms shape of the biochar were more dependent on the pyrolytic temperature than on the biomass feedstocks, which included orange peel, pine needle, and sugar cane bagasse. For LTB, the thermally altered organic matter colocalized with the carbonized matter, and the visible fine pores of the fixed carbons were plugged by the remaining volatile carbon. For HTB, most of the volatile matter was gone and the fixed matter was composed of fully carbonized adsorptive sites. Monolayer adsorption of 1-naphthol to HTB was dominant but was suppressed by phenol. In comparison, LTB displayed exceptional sorption behavior where partition and adsorption were concurrently promoted by a cosolute and elevated temperature. In addition to monolayer surface coverage, pore-filling mechanisms may contribute to the increase of adsorption fraction. Moreover, the entropy gain was a dominant force driving the partition and adsorption processes in LTB. Thus, the colocalizing partition phase and adsorptive sites in LTB are proposed to be in interencased states rather than in physical separation.Keywords:
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The rice husk fast pyrolysis was studied by using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and the pyrolysis gases were online analyzed. The effects of pyrolytic temperature and time on the pyrolysis of biomass was focused. The results show that the number and yield of product species increase with temperature below 450 ℃. The less species at lower pyrolytic temperature is of benefit to the enrichment of high value products. However, the number of product species becomes constant and the yield only changes when the temperature is over 450 ℃. The yield reaches the maximum when the temperature is 550 ℃. As the temperature increases, the optimum pyrolytic time descends. The pyrolysis of biomass with a long pyrolysis time at lower temperature is more completely than that with a shot pyrolysis time at higher temperature.
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Environmental restoration and sustainable energy solutions require effective management and utilization of agricultural crop residues to reduce greenhouse gas emissions. Biowastes are a valuable resource that can be converted into biofuels and their byproducts, solving the energy crisis and reducing environmental impact. In this study, teff husk, primarily generated in Ethiopia during the production of teff within the agro-industrial sector, is used as a feedstock for slow pyrolysis. Ethiopia generates an estimated annual production of over 1.75 million tons of teff husk, a significant portion of which is incinerated, resulting in significant pollution of the environment. This study focuses on assessing teff husk as a potential material for slow pyrolysis, a crucial stage in biochar production, to tap into its biochar-producing potential. To identify the composition of biomass, the teff husk underwent an initial analysis using thermogravimetry. The significant presence of fixed carbon indicates that teff husk is a viable candidate for pyrolytic conversion into biochar particles. The process of slow pyrolysis took place at three temperatures—specifically, 400, 450, and 500 °C. The maximum biochar yield was achieved by optimizing slow pyrolysis parameters including reaction time, temperature, and heating rate. The optimized reaction time, temperature, and heating rate of 120 min, 400 °C, and 4.2 °C/min, respectively, resulted in the highest biochar yield of 43.4 wt.%. Furthermore, biochar’s physicochemical, SEM-EDX, FTIR, and TGA characterization were performed. As the temperature of biochar increases, its carbon content and thermal stability increases as well. Unlike fuel recovery, the results suggest that teff-husk can be used as a feedstock for biochar production.
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Abstract Various studies have established that feedstock choice, pyrolysis temperature, and pyrolysis type influence final biochar physicochemical characteristics. However, overarching analyses of pre-biochar creation choices and correlations to biochar characteristics are severely lacking. Thus, the objective of this work was to help researchers, biochar-stakeholders, and practitioners make more well-informed choices in terms of how these three major parameters influence the final biochar product. Utilizing approximately 5400 peer-reviewed journal articles and over 50,800 individual data points, herein we elucidate the selections that influence final biochar physical and chemical properties, total nutrient content, and perhaps more importantly tools one can use to predict biochar’s nutrient availability. Based on the large dataset collected, it appears that pyrolysis type (fast or slow) plays a minor role in biochar physico- (inorganic) chemical characteristics; few differences were evident between production styles. Pyrolysis temperature, however, affects biochar’s longevity, with pyrolysis temperatures > 500 °C generally leading to longer-term (i.e., > 1000 years) half-lives. Greater pyrolysis temperatures also led to biochars containing greater overall C and specific surface area (SSA), which could promote soil physico-chemical improvements. However, based on the collected data, it appears that feedstock selection has the largest influence on biochar properties. Specific surface area is greatest in wood-based biochars, which in combination with pyrolysis temperature could likely promote greater changes in soil physical characteristics over other feedstock-based biochars. Crop- and other grass-based biochars appear to have cation exchange capacities greater than other biochars, which in combination with pyrolysis temperature could potentially lead to longer-term changes in soil nutrient retention. The collected data also suggest that one can reasonably predict the availability of various biochar nutrients (e.g., N, P, K, Ca, Mg, Fe, and Cu) based on feedstock choice and total nutrient content. Results can be used to create designer biochars to help solve environmental issues and supply a variety of plant-available nutrients for crop growth.
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Biochar’s ability to amend and remediate agricultural soil has been a growing interest, though the energy expenses from high-temperature pyrolysis deter the product’s use. Therefore, it is urgent to improve the pyrolysis efficiency while ensuring the quality of produced biochar. The present study utilized three types of feedstock (i.e., switchgrass, biosolid, and water oak leaves) to produce biochar via conventional slow pyrolysis and microwave pyrolysis at different temperature/energy input. The produced biochar was characterized and comprehensively compared in terms of their physiochemical properties (e.g., surface functionality, elemental composition, and thermal stability). It was discovered that microwave-mediated biochar was more resistant to thermal decomposition, indicated by a higher production yield, yet more diverse surface functional groups were preserved than slow pyrolysis-derived biochar. A nutrient (NO3-N) adsorption isotherm study displayed that microwave-mediated biochar exhibited greater adsorption (13.3 mg g−1) than that of slow pyrolysis-derived biochar (3.1 mg g−1), proving its potential for future applications. Results suggested that microwaves pyrolysis is a promising method for biochar production.
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