Environmental impact of different scenarios for the pyrolysis of contaminated mixed plastic waste

This work has received funding from the project PID2019-108826RB-I00/SRA (State Research Agency)/10.13039/501100011033, the project B-RNM-78-UGR20 (FEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades) and the project P20_00167 (FEDER/Junta de Andalucía-Ministry of Economy, Transformation, Industry, and Universities). Guillermo Garcia-Garcia is grateful for the grant “Juan de la Cierva Incorporación” funded by MCIN/AEI/10.13039/501100011033 and “ESF Investing in your future”, and the Grant ‘Marie Skłodowska-Curie Actions (MSCA) Postdoctoral Fellowship’ with Grant agreement ID: 101052284. We acknowledge funding for open access provided by Universidad de Granada/CBUA.Every day, large amounts of plastic are disposed of all over the world. Most of it is not recycled and ends up polluting the environment. Therefore, waste collection and management must be improved to reduce the environmental impact caused by plastic waste. Pyrolysis has been explored as an alternative to treat contaminated mixed plastic waste and obtain valuable materials, such as oil and char. These materials can effectively substitute fuel and activated carbon, respectively. However, the pyrolysis process also has a significant environmental impact, mainly due to gas emissions. It is important to quantify this environmental impact and compare it with alternative treatment methods to identify the best management strategy for contaminated mixed plastic waste. This study applies the Life-Cycle Assessment methodology to evaluate the environmental impact and compare it with the conventional practice of landfilling. Three different pyrolysis scenarios are considered: one in which the char is used as fuel and therefore combusted, and two in which the char is activated by carbon dioxide and potassium hydroxide, respectively, to be used as an adsorbent. Our results show that pyrolysis is environmentally superior to landfilling for the treatment of contaminated mixed plastic waste. This is mainly due to the production of oil, which substitutes commercial diesel, the production of which has a high environmental impact. Pyrolysis followed by char combustion has the lowest environmental impact of all pyrolysis scenarios considered.MCIN/AEI/10.13039/501100011033 PID2019-108826RB-I00/SRAFEDERJunta de Andalucía B-RNM-78-UGR20, P20_00167“ESF Investing in your future”‘Marie Skłodowska-Curie Actions (MSCA) Postdoctoral Fellowship’ ID: 101052284Universidad de Granada/CBU

Influencia de algunas variables en la biosorción de plomo con residuos agrícolas

En este trabajo se ha estudiado la biosorción de plomo presente en medios acuosos utilizando como sólidos sorbentes hueso de aceituna, alpeorujo y ramón del olivo, analizando la influencia sobre el proceso del pH, concentración de biosorbente, tamaño de partícula y tiempo de contacto. Los resultados muestran que en medios muy ácidos no se produce retirada de plomo con ninguno de los sólidos, aumentando el porcentaje de plomoretirado a medida que se eleva el pH del medio hastaalcanzar un valor máximo a pH 4. Así mismo, un aumentoen la concentración de biosorbente eleva el porcentaje de Pb retirado, siendo especialmente significativo este aumento para el hueso y el alpeorujo. Los resultados obtenidos en el estudio de la influencia del tamaño de partícula muestran que el porcentaje de plomo retirado disminuye a medida que aumenta el tamaño de partícula, aunque esta disminución es poco  importante para el alpeorujo y el ramón. Finalmente, el proceso de biosorción de plomo con hueso, alpeorujo y ramón se produce de forma rápida alcanzándose el equilibrio antes de los 60 minutos de operación

Characterization and Use of Char Produced from Pyrolysis of Post-Consumer Mixed Plastic Waste

In this work, the pyrolysis of post-consumer mixed plastic waste (polypropylene (PP), polystyrene (PS) and polyethylene film (PE)) is carried out. The solid product of the pyrolysis is characterized and tested for its use as adsorbent of lead present in aqueous media. The pyrolysis temperature has a great influence on the solid product yield, decreasing when the temperature increases. The highest yield to solid product obtained is from the pyrolysis of film at lower temperature (450 ◦C), reaching almost 14%. The results of product solid characterization reveal that the carbon, hydrogen and nitrogen content decreases with increasing pyrolysis temperature. Furthermore, both the ash and the volatile content are related to the pyrolysis temperature. The ash content is higher when the pyrolysis temperature is higher, while when the temperature increases, a solid product with lower volatile content is obtained. In respect to specific surface area, a higher pyrolysis temperature improves the properties of the solid product as an adsorbent. The adsorption capacity increases as the pyrolysis temperature increases, with the highest value of 7.91 mg/g for the solid obtained in the pyrolysis at 550 ◦C. In addition, adsorption capacity increases as the initial concentration of lead rises, reaching a maximum value close to 26 mg/g for an initial concentration of 40 mg/L. The Sips model is the one that best reproduces the experimental results of the adsorption process equilibrium study.PID2019-108826RB-I00/SRA (State Research Agency)/10.13039/50110001103

Performance of Different Catalysts for the In Situ Cracking of the Oil-Waxes Obtained by the Pyrolysis of Polyethylene Film Waste

The author Lucía Quesada acknowledges the financial support provided by the Ministry of Education (Spain) through Research Grant FPU18/01293.Currently, society is facing a great environmental problem, due to the large amount of plastic waste generated, most of which is not subjected to any type of treatment. In this work, polyethylene film waste from the non-selectively collected fraction was catalytically pyrolyzed at 500 ◦C, 20 ◦C/min for 2 h, in a discontinuous reactor using nitrogen as an inert gas stream. The main objective of this paper is to find catalysts that decrease the viscosity of the liquid fraction, since this property is quite meaningful in thermal pyrolysis. For this purpose, the three products of catalytic pyrolysis, the gaseous fraction, the solid fraction and the liquid fraction, were separated, obtaining the yield values. After that, the aspect of the liquid fraction was studied, differentiating which catalysts produced a larger quantity of waxy fraction and which ones did not. The viscosity of these samples was measured in order to confirm the catalysts that helped to obtain a less waxy fraction. The results showed that the zeolites Y and the zeolites β used in this study favor the obtaining of a compound with a smaller amount of waxes than for example catalysts such as FCC, ZSM-5 or SnCl2.Ministry of Education (Spain) FPU18/01293Department of Chemical Engineering, University of Granad

Biosorción de plomo con hueso de aceituna en columna de lecho fijo

En este trabajo se ha estudiado la biosorción de plomo con hueso de aceituna como sólido adsorbente, utilizando una columna de lecho fijo, analizando las principales variables de operación como altura de relleno, caudal de alimentación y concentración inicial de metal. Los resultados muestran que a medida que disminuye el caudal de alimentación aumenta el tiempo de ruptura y la retención de plomo por el hueso de aceituna. Así mismo, al aumentar la altura de lecho también se incrementa el tiempo de ruptura pasando de 45 a 180 minutos cuando la altura pasa de 4,4 a 13,4 cm. El análisis de la curva de ruptura muestra que el porcentaje retenido hasta alcanzar la saturación de la columna es significativamente mayor cuando la concentración inicial de plomo es de 10 mg/L, a partir de la cualpermanece prácticamente constante. Sin embargo, la capacidadde biosorción del hueso aumenta ligeramente al elevarse la concentración inicial de plomo, hasta alcanzar un valor máximo de 2,020 mg/g para una concentración de Pb(II) de 100 mg/L. El modelo de Thomas reproduce de forma aceptable la curva de ruptura para las tres concentraciones iniciales de plomo analizadas

Ruthenium deposited onto graphitic carbon modified with boron for the intensified photocatalytic production of benzaldehyde

The selective oxidation of added-value aromatic alcohols into aldehydes of high interest via photocatalysis has been postulated as a green and competitive oxidative reaction at mild conditions. This work is focused on the design of a tertiary graphitic carbon nitride (g-C3N4) based photocatalysts competitive for the photocatalytic production of benzaldehyde in an aqueous solution. The polymeric g-C3N4 has been modified in an easy one-pot green synthesis scheme, with the incorporation of boron in the polymeric structure and the deposition of ruthenium nanoparticles. The Ru ratio within 0.5–4% was assessed. The photocatalysts were fully characterized (XRD, FTIR, XPS, N2 isotherms, DRS-UV–visible, and PL) and the photocatalytic activity was assessed in the oxidation of benzyl alcohol to benzaldehyde in an aqueous solution. The incorporation of boron enhanced the selectivity towards benzaldehyde due to enhanced separation charges suggested by the photoluminescence technique; whereas ruthenium improved the reaction rate of the alcohol, affecting negatively the selectivity though. The sample containing 1% of Ru was selected as the optimum in terms of selectivity. The relative contribution of the involved reactive oxidant species was assessed by chemical scavenger tests, highlighting the contribution of the photo-generated holes followed by O2•‾. The analysis of the band’s alignment of the g-C3N4 before the modification with boron and ruthenium supports the enhancement by rising the redox potential of the holes released in the valence band

Recovery, separation and production of fuel, plastic and aluminum from the Tetra PAK waste to hydrothermal and pyrolysis processes

The establishment of a method of separation of materials from Tetra Pak waste to obtain products for use as raw material, fuel or other purposes was investigated in this study. First, the feasibility of hydrothermal treatment for the production of a solid fuel (hydrochar) and solid fraction formed by polyethylene and aluminum, called composite was analyzed. The results indicated that hydrothermal treatment performed at 240 ◦C yield the formation of hydrochar with good properties for its use as fuel and a composite of polyethylene and aluminum. The best conversion and separation of the cardboard and polyethylene/aluminum were obtained using 120 min as operating time. Then, the recovery of the aluminum fraction from the composite by using spent olive oil waste was studied. A partial separation of the composite layers (polyethylene and aluminum) was accomplished with improved aluminum purity for higher operating temperatures. Finally, the operating conditions of the pyrolysis process for the production of a solid (char) and high purity composite (aluminum) were optimized. The characterization results indicated that both char and aluminum resulting from the pyrolysis of the Tetra Pak at 400 ◦C still have a significant amount of polyethylene while higher purity levels of aluminum can be obtained at temperatures equal of higher than 500 ◦C

Column Leaching Tests to Valorize a Solid Waste from the Decommissioning of Coal-Fired Power Plants

The authors are grateful to the Minera de Órgiva, S.L., Granada, Spain for financial support, supply of materials used for experiments and approval of this work for publication. Also, authors would like to thank to Celso Amor for his helpful advice on various technical issues oriented to scale-up.Solid waste from the decommissioning of coal-fired power plants collected from a power plant in Spain (Puertollano, Ciudad Real) was subjected to acid leaching tests in columns to evaluate the leachability of several valuable and toxic metals (Al, Ca, Fe, K, Mg, Na, Ti, V, Cr, Mn, Ni, and Zn). First, the contaminated waste, delivered by a national company, was chemically characterized. Second, column-leaching tests were conducted using two different acid solutions (nitric and sulfuric acid). The effect of the leaching agent concentration and time of leaching were examined. The results of column leaching tests showed that different concentrations of the acid solutions leached different proportions of Al, Fe, Mg, Mn, Ni, V, and Zn, which were leached by acid solutions from the solid waste sample. In general, use of sulfuric acid at pH 0.5 resulted in better leaching. Next, a comparison between three different configurations (one single stage without recirculation, one single stage with total recirculation of leachate and leaching in two consecutive stages: one with total recirculation of leachate and another one with acid set to a pH value of 0.5 and without recirculation) was performed. At the end of the experiments, all leaching methods resulted in comparable yields for Al (0.36–0.48%), Fe (5.99–6.40%), Mg (4.43–5.11%), Mn (2.71–2.83%), Ni (12.08–12.75%), V (0.08–0.34%), and Zn (23.62–25.28%). However, better results were obtained when two consecutive stages were carried out. Additionally, the effect of forced aeration on leachability was studied. Finally, this investigation showed that hydrometallurgical treatment of contaminated solid by means of acid leaching followed by basic leaching and a water wash between these stages was a potentially feasible method for reducing hazardous levels of the residue.This research was funded by MINERA DE ÓRGIVA, S.L

Recovering Metals from Aqueous Solutions by Biosorption onto Hydrolyzed Olive Cake

Olive cake obtained as a by-product from the olive oil industry has been evaluated as biosorbent of heavy metals from aqueous solutions in batch and continuous systems (fixed-bed columns). First, a complete study of effect of hydrothermal treatment with water on biosorption capacity of resulting solid was performed. Results showed that the values of biosorption capacity increased when the particle size of material decreased and the temperature of treatment increased. Then, hydrolyzed olive cake was treated by common chemicals (hot water, nitric acid, and sodium hydroxide) and the impact of chemical treatment was analyzed. The results were well reproduced by Langmuir and Freundlich isotherm models, getting maximum experimental biosorption capacities that changed between 42.34 mg/g obtained for the solid material modified by NaOH and 14.27 mg/g obtained for the solid material modified by nitric acid. Finally, laboratory tests in fixed-bed columns were performed with four different heavy metals and at three different inlet concentrations. The biosorption capacity increased from 2.83 mg/g (Cr), 4.51 mg/g (Cu), 12.30 mg/g (Pb), and 4.10 mg/g (Zn) to 3.08 mg/g (Cr), 5.17 mg/g (Cu), 13.21 mg/g (Pb), and 5.51 mg/g (Zn) when the concentration of metal ions increased, from 50 mg/L to 200 mg/L, respectively. Also, the experimental data obtained was successfully correlated with the Thomas, Yoon–Nelson, and dose–response models.All authors are grateful to the Spanish Ministry of Economy, Industry and Competitiveness for financial support received (Project CTM2016-75977-R)

Revalorizing a Pyrolytic Char Residue from Post-Consumer Plastics into Activated Carbon for the Adsorption of Lead in Water

This work focuses on the use of a char produced during the pyrolysis of a mixture of non-recyclable plastics as a precursor for the preparation of porous activated carbon with high developed adsorption uptake of lead in water. Physical and chemical activation was used to enhance the porosity, surface area, and surface chemistry of char. The final activated carbon materials were deeply characterized through N-2 adsorption isotherms, scanning electron microscopy, Fourier transformed infrared spectroscopy, analysis of the metal content by inductively coupled plasma mass spectroscopy, and pH of point zero charge. The native char displayed a Pb adsorption uptake of 348 mg Pb center dot g(-1) and considerably high leaching of carbon, mainly organic, ca. 12%. After stabilization with HCl washing and activation with basic character activators, i.e., CO2, NaOH, and KOH, more stable adsorbents were obtained, with no organic leaching and a porous developed structure, the order of activation effectiveness being KOH (487 m(2)center dot g(-1)) > NaOH (247 m(2)center dot g(-1)) > CO2 (68 m(2)center dot g(-1)). The activation with KOH resulted in the most effective removal of Pb in water with a saturation adsorption uptake of 747 mg Pb center dot g(-1).FEDER/Junta de AndaluciaMinistry of Economy, Transformation, Industry, and Universities P20_00167 FEDER/Junta de Andalucia-Ministry of Economic Transformation, Industry, and Universities B-RNM-78-UGR2