Revalorization of Coffee Waste

One of the household methods most used to prepare the coffee beverage is the coffee dripping method, which generates millions of tons of coffee waste (CW). Its disposition without control causes environmental matters due to the high consumption of oxygen during its discomposing process. However, the high availability, low cost, and chemical composition of CW (cellulose, hemicelluloses, lignin, ashes, protein, aliphatic acids, fats, and water) make them useful material for obtaining added-value products and bioenergy. In this chapter, the state of the art of different sustainable alternatives to revalorize CW is shown. CW has been successfully applied as an adsorbent for removing pollutants from wastewater and gas, a precursor for obtaining activated carbon, and a feedstock for producing energy and valuable products using mono-process extraction and biorefinery

Studies of Adsorption of Heavy Metals onto Spent Coffee Ground: Equilibrium, Regeneration, and Dynamic Performance in a Fixed-Bed Column

Equilibrium and dynamic adsorption of heavy metals onto spent coffee ground (SCG) were studied. The equilibrium adsorption of Cd2+, Cu2+, and Pb2+ in a batch system was modeled by an ion-exchange model (IEM) based on an ion-exchange of heavy metals with calcium and protons bonded to active sites on SCG surface. The maximum amount of adsorbed metal ions obtained using the IEM was 0.12, 0.21, and 0.32 mmol/g of Cd2+, Cu2+, and Pb2+, respectively. Regeneration of SCG was evaluated using citric acid, calcium chloride, and nitric acid. The observed trend of desorption efficiency through four adsorption-desorption cycles was HNO3 > CaCl2 > C6H8O7. The effect of process variables such as flow rate and bed height during the dynamic adsorption was evaluated. Moreover, the applicability of a mass transfer model based on external mass transfer resistance, axial dispersion, and ion-exchange isotherm was evaluated, and the results were in good agreement with the experimental data for the adsorption in SCG packed column. The sensitivity analysis of the model parameters showed that axial dispersion coefficient is the most significant parameter in the dynamic simulation. The results obtained showed the potential of SCG as a low-cost material for wastewater metal removal in continuous systems

Biosorption of Cu(II) and Pb(II) from aqueous solutions by chemically modified spent coffee grains

In this research, spent coffee grains were modified with citric acid solutions (0.1 and 0.6 M) to increase the quantity of carboxylic groups improving its metal adsorption capacity. Added functional groups on modified and non-modified spent coffee grains were identified and quantified by attenuated total reflection Fourier transform infrared analyses and potentiometric titrations, respectively. These adsorbents were used for the removal of lead (II) and copper (II) from aqueous solutions at 30 °C and different pH in batch systems. In addition, adsorption–desorption experiments were conducted to evaluate the possibility of re-using the modified adsorbent. Potentiometric titrations data reveal that the quantity of carboxylic groups was increased from 0.47 to 2.2 mmol/g when spent coffee grains were modified with 0.1 and 0.6 M citric acid. Spent coffee grains treated with 0.6 M citric acid, achieved a maximum adsorption capacity of 0.77 and 1.53 mmol/g for lead (II) and copper (II), respectively, whereas non-modified spent coffee grains only reached 0.24 and 0.19 mmol/g for lead (II) and copper (II), respectively. Desorption of lead (II) and copper (II) achieved around 70 % using 0.1 N HCl for non-modified and modified spent coffee grains with 0.6 M citric acid. It is suggested that lead (II) and copper (II) species were adsorbed mainly on the carboxylic groups of modified spent coffee grains and these metals may be exchanged for hydrogen and calcium (II) ions during adsorption on non-modified spent coffee grains. Finally, the adsorption equilibrium was reached after 400 min for modified spent coffee grains with 0.6 M citric acid. Modified spent coffee grains are a promising option for removing metal cations from aqueous solutions due to its low cost and high adsorption capacity (about 10 times higher than the activated carbons)

Environmental assessment of metal-organic framework DUT-4 synthesis and its application for siloxane removal

International audienceIn this study, the effect of different solvents in metal-organic framework (MOF) synthesis was evaluated in a technical study and an environmental study. The technical study considered the octamethylcyclotetrasiloxane (D4) adsorption on MOF DUT-4 for biogas purification, while the environmental study was implemented using the Life Cycle Assessment (LCA) methodology. In addition, the obtained DUT-4 adsorbents were characterized by X-ray diffraction, N2 adsorption-desorption isotherms, solid-state 27Al magic-angle spinning nuclear magnetic resonance, scanning electron microscopy, and Fourier transform infrared spectroscopy techniques. The results indicated that technically similar materials are obtained through solvothermal synthesis with similar D4 siloxane adsorption capacities (9.8 mg/g). Conversely, hydrothermal synthesis led to a low D4 siloxane adsorption capacity (1.8 mg/g). The environmental study demonstrated that the solvothermal synthesis had the highest contribution to the environmental damage due to the use of toxic solvents in the synthesis, cleaning, and solvent exchange stages (environmental score factor up to 244 mPt). In addition, a techno-environmental impact factor was introduced to identify the most suitable synthesis route of DUT-4. The overall results pointed out that solvothermal synthesis is the best scenario for DUT-4 production due to its low environmental impact/adsorption capacity ratio (11.44). This study is a step toward a more holistic approach integrating technical and environmental criteria in MOF synthesis for adsorption applications

Siloxane removal for biogas purification by low cost mineral adsorbent

International audienceThe potential use of raw and expanded perlite as low-cost adsorbents for biogas purification has been investigated. The thermal expansion of perlite causes a reduction in the density of silanol groups from 2515.43 to 653.75 OH/nm2; in contrast, the specific surface area of perlite increased two-fold due to the thermal expansion. To determine the equilibrium adsorption capacity and the adsorption kinetics batch experiments were conducted. The adsorption capacities are in the following order: activated carbon (6.8 mg/g) andgt; silica gel (6.6 mg/g) andgt; expanded perlite (5.8 mg/g) andgt; raw perlite (5.6 mg/g) when compared at the same experimental conditions. The equilibrium adsorption data showed that perlite can be used to reduce the octamethylcyclotetrasiloxane concentration below 28 mg/m3, as recommended by leading manufacturers. The adsorption kinetics of octamethylcyclotetrasiloxane onto raw and expanded perlite followed the Linear-Driving Force model suggesting that the mass transfer is the rate-controlling step. In addition to its low cost, expanded perlite has the advantage of requiring lower desorption temperature (200 °C) for regeneration in comparison to the reported values for activated carbon (andgt;400 °C) and fast desorption kinetics (20 min), which could contribute to a cleaner production of biogas

Estudios Adsorción de Ácido Ferúlico en Quitosán

En este articulo se evalúa la factibilidad de utilizar el quitosan como adsorbente para la recuperación de ácido ferúlico de soluciones acuosas. El efecto del pH sobre la capacidad de adsorción fue estudiada, siendo a pH 2 en donde se obtiene la mejor capacidad de adsorción (80 mg AF/g), además se observo una disminución de la capacidad del quitosan para adsorber ácido ferúlico conforme se incrementa el pH. En los estudios cinéticos, se demostró que el tiempo para alcanzar el equilibrio fue de 60 min independientemente de la concentración de adsorbente utilizado y el modelo de pseudo- primer orden fue el modelo que mejor se ajusto a los datos experimentales. Estudios de equilibrio de adsorción fueron realizados a diferentes temperaturas (30-50 ºC), la capacidad de adsorción disminuyo conforme se incrementa la temperatura, el modelo de Langmuir fue ajustado a los datos experimentales y la máxima capacidad de adsorción (432 mg AF g-1) fue obtenida a 30 ºC

Erratum to: Biosorption of Cu(II) and Pb(II) from aqueous solutions by chemically modified spent coffee grains

The original version of this article unfortunately contained mistakes. The presentations of Figs. 1 and 2 were incorrect. The correct versions of the figures are given in following page

Response surface methodology for lead biosorption on Aspergillus terreus

A central composite face-centered design was used to study and to optimize lead biosorption from aqueous solution on Aspergillus terreus biomass. Four factors such as stirring speed, temperature, solution pH and biomass dose at different levels were studied.The hierarchical quadratic model were established by adding replicates at the central point and axial points to the initial full factorial design (24). The percentage removal of lead was affected by biomass dose, pH, and interactions between pH and biomass dose, pH and stirring speed, pH and temperature. The hierarchical quadratic model described adequately the response surface based on the adjusted determination coefficient (R2Adj= 0.97) and the adequate precision ratio (42.21). According to this model, the optimal conditions to remove lead completely from aqueous solutions (at initial lead concentration of 50 mg/L and solutions of 100 mL) with Aspergillus terreus were at pH 5.2, 50°C, stirring speed of 102/min and a biomass dose of 139 mg.The response surface methodology can be used to determine the optimal conditions for metal adsorption on several adsorbents. In addition, results reported in this research demonstrated the feasibility of employing A. terreus as biosorbent for lead removal

Aplicación de la cianobacteria Spirulina sp. en la remoción y recuperación del colorante rojo congo de muestras acuosas.

En este trabajo se utilizó la biomasa de Cianobacteria Spirulina sp. en un sistema Bach, para remover el colorante ácido Rojo Congo (RC). Se estudió el efecto de variables de operación tales como dosis de biomasa. tiempo de contacto pH inicial y temperatura. Las mejores condiciones de operación para la remoción de Re fueron: dosis de biomasa de 1 gIL, pH 2, temperatura de 25 oC y tiempo de contacto de 2 horas. Los datos experimentales del equilibrio de biosorción se ajus1aron mejor al modelo de Langmuir y la cinética de adsorción siguió el modelo de pseudosegundo orden. La máxima capacidad de biosorción experimental de la biomasa fue de 418.70 mglg y eficiencia de recuperación del colorante fue superior a193%. Estos resultados sugieren que la biomasa de Spirulina sp., un adsorbente de bajo costo, presenta potencial para remover colorantes amónicos de efluentes industriales

Chlorella sp.: potencial biomaterial para tratamiento de agua contanunada con colorantes

Eneste trabajo se evaluó el potencial de la biomasa de Chlorella sp. paralaremoci6n del colorante tóxico Rojo Congo en muestras de agua contaminada. Se caracterizó la biomasa de Chlorella sp en la que mediante su espectro de FTIR se confirmó la presencia de grupos amino, carboxilo, tiol y fosfatos. As! mismo se mediante potenciometrla se encontró que el punto de carga cero (pCC) de la biomasa correspondió a un pH de 6.4 Y la concentración de sitios activos fue de 0.65 moq/g de sitios ácidos y 0.6 moq/g de sitios básicos. Las pruebas de biosorci6n con la biomasa de Chlorella sp. Mostraron una alta eficiencia de laremoci6n, superior a190% misma que se mantiene en al menos tres ciclos de sorciÓD-desorci6n. Los resultados obtenidos sugieren que cIuso de la biomasa de Ch10rella sp. como biosorbentc de colorantes en agua contaminada es atractivo tanto desde el punto de vista económico como ambiental