Determinación de parámetros cinéticos en la biosorción de Cromo (VI) en solución acuosa

The contamination of aquatic bodies by heavy metals is a growing environmental problem, making more critical the study and development of new technologies and materials that can be used for the removal of this type of pollutants. Thus, adsorption arises using residual materials as a sustainable alternative for the solution to this problem. In the present study, the use of plantain peels in the adsorption of Cr (VI) in a batchsystem is proposed, establishing the kinetics of the process at different temperature conditions, particle size and amount of adsorbent. The fit of the data was done using the theoretical models of pseudo-first-order,pseudo-second-order and Elovich. From the data, it is established that the pseudo-second-order and Elovich models show a better adjustment, so that the adsorption in the material occurs on two adsorption sites and that such process is related to chemical adsorption. The maximum adsorption capacity of Cr (VI) was found at a condition of 0.0306 g, 0.6775 mm and 55°C at a time of 420 min establishing the efficient use of plantain peels for the removal of the ion metallic in the studio.La contaminación de cuerpos acuáticos por metales pesados es un problema ambiental creciente haciendo cada vez más importante el estudio y desarrollo de nuevas tecnologías y materiales que puedan ser usados para la remoción de este tipo de contaminantes. Así surge la adsorción usando materiales residuales como una alternativa sostenible para la solución de esta problemática. En el presente estudio se propone el uso de las cáscaras de plátano en la adsorción de Cr (VI) en un sistema por lotes estableciendo la cinética del proceso a diferentes condiciones de temperatura, tamaño de partícula y cantidad de adsorbente. El ajuste de los datos fue hecho usando los modelos teóricos de pseudo-primer orden, pseudo-segundo orden y Elovich. De los datos se establece que son los modelos de pesudo-segundo orden y Elovich los que muestran un mejor ajuste determinado así que la adsorción en el material se da sobre dos sitios de adsorción y que tal proceso está relacionado con una adsorción química. La máxima capacidad de adsorción de Cr (VI) fue encontrada a una condición de 0.0306 g, 0.6775 mm y 55°C a un tiempo de 420 min estableciendo el uso eficiente de cáscaras de plátano para la remoción del ion metálico en estudio

Electrocoagulación como alternativa para eliminación de cromo (VI) en solución

Context: The contamination of water sources by the discharge of effluents contaminated with chromium (VI) is a current environmental problem because it is a toxic pollutant for humans, animals, plants, and microorganisms; it can be carcinogenic and has a high solubility in an aqueous environment. This research aims to study the electrochemical removal of hexavalent chromium by electrocoagulation using iron and aluminum electrodes with monopolar configuration, evaluating the effect of residence time, voltage, and the number of electrodes on the removal efficiency. Methodology: The experiments were conducted in a 3L batch electrocoagulation cell, using 10 and 6 aluminum and stainless steel plates as electrodes, connected at a distance of 1.5 cm in a monopolar configuration in parallel to the power source. Contaminated solution with Cr (VI) was treated at a concentration of 50 mg/L, evaluating two levels of residence time (20 and 30 min), voltage (20 and 30 V), and the number of electrodes (6 and 10 electrodes). Results: After the electrocoagulation removal tests, it was obtained removal percentages between 60.15 and 92.9%. The most significant positive variable in the process was the increase in the residence time. It can be inferred that electrocoagulation performs better at lower voltages and longer residence times and that the joint effect of the increase of the number of electrodes and the contact time would increase the performance of the process, achieving greater removal. Conclusions: The process of reduction of chromium (VI) by electrocoagulation has the potential to be used for the cost-effective removal of heavy metals from waterContexto: La contaminación de los cuerpos de agua, producto de los vertimientos de efluentes contaminados con Cromo (VI), es una problemática ambiental ampliamente estudiada, debido a los efectos tóxicos de este contaminante sobre la salud humana y el ambiente. El objetivo del presente trabajo es estudiar la eliminación de cromo hexavalente usando el método de electrocoagulación con electrodos de hierro y aluminio en configuración monopolar. Se evaluó el efecto del tiempo de residencia, del voltaje y del número de electrodos sobre la eficiencia de remoción. Metodología: Los experimentos se realizaron en una celda de electrocoagulación por lotes de 3 L, utilizando 10 y 6 placas de aluminio y acero inoxidable, respectivamente, como electrodos conectados a una distancia de 1,5 cm en configuración monopolar, en paralelo a la fuente de energía. Se trató una solución contaminada con Cr(VI) a una concentración de 50 mg/L, evaluando dos niveles de tiempo de residencia (20 y 30 min), voltaje (20 y 30 V) y número de electrodos (6 y 10 electrodos). Resultados: Se obtuvieron porcentajes de remoción entre 60,15 y 92,9%. Se encontró que la variable con mayor incidencia positiva sobre el proceso es el aumento del tiempo de residencia. Se puede inferir que la electrocoagulación se desempeña mejor a voltajes inferiores y tiempos de residencia mayores, y que el efecto conjunto del aumento de la cantidad de electrodos y el tiempo de contacto incrementa el rendimiento del proceso, logrando así mayor remoción. Conclusiones: El proceso de reducción de cromo (VI) mediante electrocoagulación tiene el potencial de utilizarse para la eliminación de metales pesados del agua de manera rentable

Evaluation of Parameters in the Removal of Linear Alkylbenzene Sulfonate Anionic Surfactant Using Electrocoagulation

The objective of the present investigation was to construct an electrocoagulation cell in a batch system and to evaluate its capacity to remove the anionic surfactant of the linear alkylbenzene sulfonate (LAS), which is present in gray water determining the effect of the type of electrodes (Al or Fe), distance between electrodes (1, 1.5 and 2 cm) and voltages (10, 15 and 20 V). The experimental tests were carried out for 20 min. The dimensions of the short wave electrolysis cell built in glass were 26 cm long, 7 cm wide and 12 cm high, with 10 electrodes of 12x6 cm supported by a PVC structure. The concentration of LAS in the solution was determined by employing UV-Vis spectrometry applying the Methylene Blue Active Substances (MBAS) method. A higher removal of 65.55% was obtained when aluminum electrodes were used, and 69.11% with iron electrodes a separation of 1.5 cm and a voltage of 20 V, presenting less change in pH, conductivity, and energy consumption when using the Al3 electrode. When evaluating the effect of time at the best experimental configuration (Al, 1.5 cm, 20 V) it was established that the removal efficiency increased to 75.13% in 60 min. Electrocoagulation with aluminum electrodes is presented as an efficient alternative for the removal of LAS in solution

Influence of the bed height on the dynamic behavior of a fixed-bed column during mercury biosorption

Se determinó el impacto de la altura del lecho en la remoción de Hg (II), presente en solución sobre biomasa residual de cáscara de cacao en sistema continuo de lecho fijo, evaluando el rendimiento de la densidad de empaque. El trabajo experimental estuvo fundamentado en: preparación de la biomasa, diseño y montaje de la unidad de adsorción y modelado matemático, considerando como variables intervinientes en el proceso la concentración inicial del metal, pH, velocidad de flujo y tamaño de partícula y como variable independiente incidente la densidad de empaque mg biomasa/volumen del lecho, traducido en altura en cm de empaque. Los análisis FTIR de la cáscara muestran la presencia de grupos funcionales que favorecen la adsorción de iones metálicos. La concentración de Hg (II) se midió por espectroscopia UV/vis; se obtuvo una capacidad máxima de adsorción fue de 99.62 % para el lecho de 10g (7.5 cm). Además, el modelo de Thomas fue el que mejor ajustó los datos experimentales. A partir de estos resultados, se concluye que la cáscara de cacao tiene potencial para ser utilizado como bioadsorbente de Hg (II) en solución y que el aumento de la altura del lecho en el sistema continuo favoreció la remoción del contaminante.This study evaluated the packing density of residual biomass of cocoa bean husk as adsorbent of Hg (II) dissolved in an aqueous solution inside a continuous fixed-bed system. The effects of the height of the bed on the removal of the pollutant were evaluated. This experimental work was based on biomass preparation, adsorber design and assembly, and mathematical modelling. The variables considered in the process were initial concentration of the metal, pH, flow rate and particle size. The incident-independent variable was the packing density (mg biomass/bed volume), which translated into the height (cm) of the packing. The FTIR analyses of the husk revealed the presence of functional groups in the spectrum that favour the adsorption of the metal. The residual concentration of the solution was measured by UV/Vis spectroscopy; the maximum adsorption capacity was 99.62%, by the 10g (7.5 cm) bed. In addition, the Thomas model was the best-fitting for the experimental data. On the basis of these results, we concluded that cocoa bean husk has potential to be used as bioadsorbent of Hg (II) from aqueous solutions and that the increase in bed height in the continuous system favours the removal of the pollutant

Evaluation of Three Biomaterials from Coconut Mesocarp for Use in Water Treatments Polluted with an Anionic Dye

Coconut consumption leads to the generation of a large number of fibrous residues such as epicarp and mesocarp. In this study, bioadsorbents were prepared from coconut shells (CS), coconut cellulose (CC) and treated coconut cellulose (MCC) with cetyl trimethyl ammonium chloride (CTAC) for the elimination of Congo red (CR) in a watery solution. The impact of the adsorbent quantity (15, 25 and 35 mg) and initial concentration (40, 70 and 100 mg/L) were evaluated. Fourier transform infrared spectra (FTIR) confirmed the existence of OH−, C=O, COOH and CH2 groups in the adsorbents as well as the deformation of the bands between 3400 and 3800 cm−1 after the adsorption of CR, which was attributed to its capture in the bioadsorbent. From the bromatological analysis, a content of 48.94% lignin, 35.99% cellulose and 10.51% hemicellulose was found. SEM images showed a lignocellulosic essential surface origin for all adsorbents with presence of folds, roughness of an irregular exposed area and fibrous filaments. The average particle size was 0.45 mm and adsorbents had a mean porosity of 0.58. Increasing the initial concentration had a beneficial influence on the removal efficiency of CR, achieving a 99.9% removal with MCC. CS showed slow kinetics in the initial stages whereas CC and MCC achieved 78% and 99.98% removal at 120 min, respectively; an equilibrium was reached at 480 and 20 min, respectively. MCC, CC and CS achieved a maximum qe of 256.12 mg/g, 121.62 mg/g and 17.76 mg/g, respectively

Evaluation of Three Biomaterials from Coconut Mesocarp for Use in Water Treatments Polluted with an Anionic Dye

Coconut consumption leads to the generation of a large number of fibrous residues such as epicarp and mesocarp. In this study, bioadsorbents were prepared from coconut shells (CS), coconut cellulose (CC) and treated coconut cellulose (MCC) with cetyl trimethyl ammonium chloride (CTAC) for the elimination of Congo red (CR) in a watery solution. The impact of the adsorbent quantity (15, 25 and 35 mg) and initial concentration (40, 70 and 100 mg/L) were evaluated. Fourier transform infrared spectra (FTIR) confirmed the existence of OH−, C=O, COOH and CH2 groups in the adsorbents as well as the deformation of the bands between 3400 and 3800 cm−1 after the adsorption of CR, which was attributed to its capture in the bioadsorbent. From the bromatological analysis, a content of 48.94% lignin, 35.99% cellulose and 10.51% hemicellulose was found. SEM images showed a lignocellulosic essential surface origin for all adsorbents with presence of folds, roughness of an irregular exposed area and fibrous filaments. The average particle size was 0.45 mm and adsorbents had a mean porosity of 0.58. Increasing the initial concentration had a beneficial influence on the removal efficiency of CR, achieving a 99.9% removal with MCC. CS showed slow kinetics in the initial stages whereas CC and MCC achieved 78% and 99.98% removal at 120 min, respectively; an equilibrium was reached at 480 and 20 min, respectively. MCC, CC and CS achieved a maximum qe of 256.12 mg/g, 121.62 mg/g and 17.76 mg/g, respectively

Selective and Competitive Adsorption of Anions in Solution on Porous Adsorbent from Zea mays Steams: Kinetic and Equilibrium Study

Surface modification can improve the adsorption capacity of biochar. Biochar was produced from corn stalks (Zea mays) by pyrolysis at 520 °C, activated with sulfuric acid (H2SO4) using impregnation ratios of biomass weight: volume 1:2 (B 1:2) and 1:3 (B 1:3). The kinetic study showed that the equilibrium is reached at 180 min; the maximum adsorption capacity of nitrate and sulphate was obtained with B 1:2 and for phosphate with B 1:3. The adsorption of nitrate and phosphate with the two biochars presented a good fitting to the pseudo-first order and pseudo-second-order model, while that of sulphate for B 1:2 is described by Elovich’s model. Freundlich’s model describes the equilibrium of adsorption of nitrate and phosphate using B 1:2 and B 1:3, while Dubinin–Radushkevich adjusts the removal of sulphate for C 1:2 and C 1:3; therefore it is suggested that adsorption occurs in multilayers. The multicomponent study evidences the preference of biocarbon for phosphate, without indicating competition for the active centers of the material among the anions studied

Batch and Packed Bed Column Study for the Removal of Cr (VI) and Ni (II) Using Agro-Industrial Wastes

The objective of this study was to prepare bio adsorbents from agro-industrial wastes from yam starch (YSR) and plantain (PSR) production for its use in the removal of Cr (VI) and Ni (II) in aqueous solution in batch and continuous packed-bed column systems. Bromatological analysis showed that the biomaterials are rich in cellulose, lignin, hemicellulose, and SEM micrographs that evidence a mesoporous structure characteristic of materials of lignocellulosic origin. FTIR evidenced functional groups such as hydroxyl, carbonyl, and methyl, possibly involved in the uptake of metal ions. EDS and FTIR analysis after adsorption confirmed that the retention of the metals on the surface of the adsorbent materials was successful. Cr (VI) and Ni (II) removal efficiencies above 80% were achieved using YSR and PSR in batch systems at the different conditions evaluated. The optimum conditions for removing Ni (II) on PSR were a bed height of 11.4 cm and a temperature of 33 °C, while for YSR, they were: 43 °C and 9 cm for temperature and bed height respectively. The variable with the most significant influence on the removal of Cr (VI) in a batch system on the two bio adsorbents was temperature. In contrast, the adsorbent dose and temperature are relevant factors for PSR Ni (II) removal. Therefore, the residues from the preparation of yam and plantain starch have high potential for removing heavy metals from wastewater and are presented as an alternative for their final disposal

Caracterización de la Opuntia ficus-indica para su uso como coagulante natural

<p class="MsoNormal" style="margin-bottom: 0.0001pt;"><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;">Título en inglés: C</span></strong><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN">haracterization of</span></strong><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN"> </span></strong><strong><em><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN">Opuntia ficus</span></em></strong><strong><em><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN">-indica</span></em></strong><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN"> </span></strong><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN">for using</span></strong><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN"> </span></strong><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN">as a</span></strong><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN"> </span></strong><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN">natural</span></strong><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN"> </span></strong><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="EN">coagulant</span></strong></p><p class="MsoNormal" style="margin-bottom: 0.0001pt;"><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="ES-CO">Título corto: Caracterización de <em>Opuntia </em></span></strong><strong><em><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="ES-CO">ficus</span></em></strong><strong><em><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="ES-CO">-indica </span></em></strong><strong><span style="font-size: 10pt; font-family: 'Times New Roman', serif;" lang="ES-CO">para coagulante natural</span></strong></p><p class="MsoNormal" style="margin-bottom: 0.0001pt;"><strong><span style="font-size: 10.0pt; font-family: " lang="ES-CO">Resumen</span></strong></p><p class="MsoNormal" style="margin-bottom: 0.0001pt; text-align: justify;"><span style="font-size: 12.0pt; font-family: " lang="ES-CO">Actualmente municipios de la Costa Atlántica Colombiana no cuentan con suministro de agua potable. La aplicación artesanal de la Tuna (<span class="hps"><em>Opuntia</em></span> <span class="hps"><em>ficus</em></span><em>-indica</em>)  como coagulante es una práctica tradicional en comunidades rurales. En esta investigación se realiza la caracterización del tallo de la Tuna que crece de manera silvestre en el departamento de Bolívar, y del polvo extraído de esta planta, con el fin de identificar componentes asociados a su poder coagulante para la remoción de turbidez y de color en aguas crudas. Las pencas de la planta se sometieron a operaciones de corte, pelado, secado, molienda, tamizado y despigmentado para obtener el coagulante. El rendimiento del proceso global fue de 65g de coagulante/Kg de material vegetal. Los resultados indicaron que la penca contiene alto porcentaje de humedad y pequeñas proporciones de saponinas, flavonoides, sales minerales de calcio y hierro; lo cual permitió concluir que estos metabolitos y sales no son los responsables de su poder coagulante debido a las cantidades poco significativas en las que se encuentran. Se consideró que otras especies química tales como el ácido poligalacturónico y compuestos algínicos son realmente los que le confieran la cualidad al biomaterial. También, se evaluó el poder coagulante del material extraído, se analizó el efecto de tres dosis sobre el color, la turbidez y el pH del agua tratada. Los resultados indicaron que tiene la capacidad de remover 50% del color y 70% de turbidez de aguas crudas con alta turbidez inicial, y que <span style="letter-spacing: -.1pt;">no altera significativamente su pH.  </span></span></p><p class="MsoNormal" style="margin-bottom: 0.0001pt;"><strong><span style="font-size: 10.0pt; font-family: " lang="ES-CO">Palabras clave: </span></strong><span style="font-size: 10.0pt; font-family: " lang="ES-CO">aguas crudas, clarificación, flavonoides, saponinas, turbidez<span><span style="letter-spacing: -.1pt;">. </span></span></span></p><p class="MsoNormal" style="margin-bottom: 0.0001pt;"><strong><span style="font-size: 10.0pt; font-family: ">Abstract</span></strong></p><p class="MsoNormal" style="margin-bottom: 0.0001pt; text-align: justify;"><span style="font-size: 10.0pt; font-family: " lang="EN">Currently, municipalities in the Colombian Atlantic Coast do not have potable water supply. The implementation of the Tuna as a coagulant is a traditional practice in rural communities, but is used in craft way. In the present investigation, the characterization of the stalk of Tuna (<em>Opuntia ficus-indica</em>) growing in the wild in the Bolivar department, and of the powder extracted from this plant was realized with the purpose to identify components associated with its coagulant power to remove color and turbidity in raw water. The stalks of this plant were subjected to cutting, peeling, drying, grinding, sieving and depigment for obtaining the coagulant. The overall process yield was 65g of coagulant/kg of vegetal material. The results also indicated that the stalk of Tuna contains high moisture content and low amounts of saponins, flavonoids, minerals, calcium and iron. It allowed concluding that these metabolites and salts are not responsible of the coagulant power of plant due to the insignificant amounts in which they are present. Therefore, it is presumed that other chemical species such as polygalacturonic acid and alginic compounds are those that confer the quality to the biomaterial. Also, the coagulant power of extracted material was evaluated. The effect of three dosis on the color, turbidity and pH of trated water was analized. The results indicated that it has the capacity to remove 50% of color and 70% of turbity from crude water with high initial turbidity. Also, it does not affect significantly its pH.</span></p><p class="MsoNormal" style="margin-bottom: 0.0001pt; text-align: center;" align="center"> </p><p class="MsoNoSpacing" style="text-align: justify;"><span><strong><span style="font-size: 10.0pt; font-family: ">Key words: </span></strong></span><span><span style="font-size: 10.0pt; font-family: ">raw </span></span><span style="font-size: 10.0pt; font-family: ">water, clarification, flavonoids, saponoids, turbidity.</span></p><p class="MsoNoSpacing" style="text-align: justify;"><span style="font-size: 10.0pt; font-family: "><strong>Resumen</strong></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; text-align: justify;"><span style="font-size: 10.0pt; font-family: " lang="ES-CO">Actualmente municipios de la Costa Atlántica Colombiana no cuentan con suministro de agua potable. La aplicación artesanal de la Tuna (<span class="hps"><em>Opuntia</em></span> <span class="hps"><em>ficus</em></span><em>-indica</em>)  como coagulante es una práctica tradicional en comunidades rurales. En esta investigación se realiza la caracterización del tallo de la Tuna que crece de manera silvestre en el departamento de Bolívar, y del polvo extraído de esta planta, con el fin de identificar componentes asociados a su poder coagulante para la remoción de turbidez y de color en aguas crudas. Las pencas de la planta se sometieron a operaciones de corte, pelado, secado, molienda, tamizado y despigmentado para obtener el coagulante. El rendimiento del proceso global fue de 65g de coagulante/Kg de material vegetal. Los resultados indicaron que la penca contiene alto porcentaje de humedad y pequeñas proporciones de saponinas, flavonoides, sales minerales de calcio y hierro; lo cual permitió concluir que estos metabolitos y sales no son los responsables de su poder coagulante debido a las cantidades poco significativas en las que se encuentran. Se consideró que otras especies química tales como el ácido poligalacturónico y compuestos algínicos son realmente los que le confieran la cualidad al biomaterial. También, se evaluó el poder coagulante del material extraído, se analizó el efecto de tres dosis sobre el color, la turbidez y el pH del agua tratada. Los resultados indicaron que tiene la capacidad de remover 50% del color y 70% de turbidez de aguas crudas con alta turbidez inicial, y que <span style="letter-spacing: -.1pt;">no altera significativamente su pH.  </span></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt;"><strong><span style="font-size: 10.0pt; font-family: " lang="ES-CO">Palabras clave: </span></strong><span style="font-size: 10.0pt; font-family: " lang="ES-CO">aguas crudas, clarificación, flavonoides, saponinas, turbidez<span><span style="letter-spacing: -.1pt;">. </span></span></span></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt;"><strong><span style="font-size: 10.0pt; font-family: ">Abstract</span></strong></p> <p class="MsoNormal" style="margin-bottom: 0.0001pt; text-align: justify;"><span style="font-size: 10.0pt; font-family: " lang="EN">Currently, municipalities in the Colombian Atlantic Coast do not have potable water supply. The implementation of the Tuna as a coagulant is a traditional practice in rural communities, but is used in craft way. In the present investigation, the characterization of the stalk of Tuna (<em>Opuntia ficus-indica</em>) growing in the wild in the Bolivar department, and of the powder extracted from this plant was realized with the purpose to identify components associated with its coagulant power to remove color and turbidity in raw water. The stalks of this plant were subjected to cutting, peeling, drying, grinding, sieving and depigment for obtaining the coagulant. The overall process yield was 65g of coagulant/kg of vegetal material. The results also indicated that the stalk of Tuna contains high moisture content and low amounts of saponins, flavonoids, minerals, calcium and iron. It allowed concluding that these metabolites and salts are not responsible of the coagulant power of plant due to the insignificant amounts in which they are present. Therefore, it is presumed that other chemical species such as polygalacturonic acid and alginic compounds are those that confer the quality to the biomaterial. Also, the coagulant power of extracted material was evaluated. The effect of three dosis on the color, turbidity and pH of trated water was analized. The results indicated that it has the capacity to remove 50% of color and 70% of turbity from crude water with high initial turbidity. Also, it does not affect significantly its pH.</span></p> <p class="MsoNoSpacing" style="text-align: justify;"><span><strong><span style="font-size: 10.0pt; font-family: ">Key words: </span></strong></span><span><span style="font-size: 10.0pt; font-family: ">raw </span></span><span style="font-size: 10.0pt; font-family: ">water, clarification, flavonoids, saponoids, turbidity.</span></p

Equilibrium, Kinetics and Thermodynamics of Chromium (VI) Adsorption on Inert Biomasses of Dioscorea&nbsp;rotundata and Elaeis&nbsp;guineensis

Adsorption equilibrium and kinetics on lignocellulosic base adsorbents from oil palm bagasse (OPB) and yam peels (YP) were studied for the removal of hexavalent chromium present in aqueous solution, in a batch system, evaluating the effect of temperature, adsorbent dose and particle size on the process. Isotherms were fitted to Langmuir, Freundlich and Dubinin&ndash;Radushkevich isothermal models. Kinetic data were adjusted to the pseudo-first-order, pseudo-second-order and Elovich models. Thermodynamic parameters were estimated by the van&rsquo;t Hoff method. From characterization of adsorbents, the presence of a porous surface typical of lignocellulosic materials was found, with hydroxyl, amine and carboxyl functional groups. It was also found that the highest adsorption capacity was obtained at 0.03 g of adsorbent, 55 &deg;C and 0.5 mm, reporting an adsorption capacity of 325.88 and 159 mg/g using OPB and YP, respectively. The equilibrium of adsorption on OPB is described by Langmuir and Freundlich isotherms, while that of YP is described by Dubinin&ndash;Radushkevich&rsquo;s model, indicating that the adsorption is given by the ion exchange between the active centers and the metallic ions. A maximum adsorption capacity was obtained of 63.83 mg/g with OPB and 59.16 mg/g using YP, according to the Langmuir model. A kinetic study demonstrated that equilibrium time was 200 min for both materials; kinetic data were described by pseudo-second-order and Elovich models, thus the mechanism of Cr (VI) adsorption onto the evaluated materials is dominated by a chemical reaction. The thermodynamic study determined that the elimination of YP is endothermic, irreversible and not spontaneous, while for OPB it is exothermic, spontaneous at low temperatures and irreversible