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

Activated char from the co-pyrolysis of polystyrene and olive stone mixtures for the adsorption of CO2

Yogurt plastic containers made of polystyrene (PS), olive stone, and mixtures of both have been converted into activated carbon materials transforming them firstly into char via pyrolysis and secondly with activation using either KOH or H2SO4. The pyrolysis of the olive stone gave a higher yield of material than the plastic PS. However, the activation of the PS char with KOH was more effective, reaching surface areas of 508 vs 194 m2 g−1 of the corresponding prepared with olive stone. The prepared materials were tested as CO2 adsorbent in thermobalance and fixed-be column assays. The materials activated with H2SO4 slightly enhanced the adsorption ability of the original char but were far from the performance obtained with KOH activation. The CO2 isotherms showed high synergy of CO2 uptake and selectivity when using activated chars prepared with the char from the mixture of raw materials, specially at a 1:1 mass ratio. The isosteric heat of adsorption values were those expected for a physisorption process. Further experiments in a fixed-bed column were also studied at atmospheric pressure at different inlet CO2 concentrations (10–50%). The CO2 retention increased as the partial CO2 pressure rose. Besides, a very similar performance of the material prepared with plastic and olive stones was obtained at 50%, i.e. 220 and 197 mg g−1 respectively. At low CO2 concentrations, the materials enriched with plastic displayed better performance than those prepared with olive stone. Cycles of adsorption-desorption were carried out in the column to assess the stability of the materials. The curves obtained did not display any substantial change, demonstrating the lack of adsorption retention

Fixed-bed CO2 adsorption onto activated char from the pyrolysis of a non-recyclable plastic mixture from real urban residues

The potential use of activated char obtained from the pyrolysis of a mixture of non-recyclable plastics for the adsorption of CO2 in fixed-bed columns has been explored. The rejected fraction of plastics collected in a municipal solid treatment plant was pyrolyzed and the resulting char residue was activated to develop a porous carbonaceous material. The dynamic behavior of CO2 adsorption was assessed by the breakthrough curves obtained in continuous column tests. Among all the available models, the curves were successfully fitted to the dose-response model. The effect of adsorption temperature (15–45 ºC), the inlet CO2 concentration (10–40 %, vol.), and the adsorbent length of the bed (loadings, 1–2 g) on the efficiency of the process was evaluated by the surface response methodology applying an adaptative neural fuzzy inference system (ANFIS). A temperature rise exerted a negative effect on the adsorption capacity due to the physisorption properties of the process, the fed CO2 concentration displayed a positive effect and the fixed-bed length did not play a remarkable influence.Project PID2019-108826RB-I00/SRA (State Research Agency)/10.13039/501100011033Project B-RNM-78-UGR20 (FEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades)Funding for open access charge: Universidad de Granada/ CBU

N-acetylcysteine selectively antagonizes the activity of imipenem in Pseudomonas aeruginosa by an OprD-mediated mechanism

The modulating effect of N-acetylcysteine (NAC) on the activity of different antibiotics has been studied in Pseudomonas aeruginosa. Our results demonstrate that, in contrast to previous reports, only the activity of imipenem is clearly affected by NAC. MIC and checkerboard determinations indicate that the NAC-based modulation of imipenem activity is dependent mainly on OprD. SDS-PAGE of outer membrane proteins (OMPs) after NAC treatments demonstrates that NAC does not modify the expression of OprD, suggesting that NAC competitively inhibits the uptake of imipenem through OprD. Similar effects on imipenem activity were obtained with P. aeruginosa clinical isolates. Our results indicate that imipenem-susceptible P. aeruginosa strains become resistant upon simultaneous treatment with NAC and imipenem. Moreover, the generality of the observed effects of NAC on antibiotic activity was assessed with two additional bacterial species, Escherichia coli and Acinetobacter baumannii. Caution should be taken during treatments, as the activity of imipenem may be modified by physiologically attainable concentrations of NAC, particularly during intravenous and nebulized regimes.Ministerio de Ciencia e Innovación y Instituto de Salud Carlos III y European Development Regional Fund (ERDF) y Spanish Network for Research in Infectious Diseases REIPI RD12/0015 FIS PI13/0006

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

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)