Eduardo M. Cuerda-Correa

On the use of carbon blacks as potential low-cost adsorbents for the removal of non-steroidal anti-inflammatory drugs from river water

The adsorption of two non-steroidal anti-inflammatory drugs (NSAIDs), namely naproxen and ketoprofen, has been studied. Low-cost carbonaceous materials such as carbon blacks have been used as the adsorbents. The influence of temperature (20-60 degrees C), pH (3-11), ionic strength (0.01-0.1M), textural properties of the adsorbents (S(BET) and pore volumes) and aqueous matrix on the adsorption process has been analyzed. The adsorption isotherms have been determined both in milli-Q aqueous solution and water from the Guadiana river. Ionic strength and pH exert a noticeable influence on the process. In general, the removal is favored at low values of temperature and pH. On the contrary, an increase of the ionic strength seems to favor the adsorption process. The use of more porous adsorbents results in a more effective removal of the pollutants. Finally, the use of natural river water results in a noticeable increase of the removal capacity of naproxen and, particularly, ketoprofen. The experimental results proved that, under the optimal operation conditions, up to 517mg/g of naproxen and 400mg/g of ketoprofen may be adsorbed, which demonstrates the promising potential of these adsorbents for the removal of the pharmaceuticals under study.

Removal of chlorophenols in aqueous solution by carbon black low-cost adsorbents. Equilibrium study and influence of operation conditions

The adsorption process of chlorophenols (CPs) by low-cost adsorbents such as carbon blacks has been studied. The influence of different parameters such as temperature, pH, ionic strength and textural properties of the adsorbents on the adsorption process of pentachlorophenol has been analyzed. The adsorption process is exothermal and parameters such as pH and ionic strength exert a noticeable influence on the adsorption capacity of the solute. These parameters influence the adsorption capacity in an opposite manner. Thus an increase in pH seems to unfavor the adsorption process, whereas the adsorption capacity increases with increasing ionic strength. In order to analyze the influence of the number of chlorine atoms in the molecule of solute the adsorption process of different chlorophenols (i.e., 4-chlorophenol, 3,5-dichlorophenol, 2,4,6-trichlorophenol and 2,3,4,6-tetrachlorophenol) was analyzed. As the number of chlorine atoms (and thus the volume of the molecule) increases, the penetration of the solute through the porous texture of the adsorbent is difficult and, consequently, the adsorption capacity decreases.

Preparation of activated carbons from walnut wood: a study of microporosity and fractal dimension

Agricultural and forest residues constitute an extraordinarily important source of precursors for the manufacture of activated carbons. Activated carbons are well known as porous solids with a highly developed apparent surface area. In the present work, activated carbon has been prepared from forest residues of walnut tree wood (a raw material not studied until now) by physical activation. Raw material has been carbonized between 573 and 1073 K and afterwards activated in air at temperatures between 623 and 823 K. The apparent surface area, micropore volume, mesopore volume and fractal dimension of the samples prepared have been calculated.

On the use of a natural peat for the removal of Cr(VI) from aqueous solutions

A natural peat has been used as an adsorbent for the removal of hexavalent chromium from aqueous solution. The peat was firstly characterized in terms of particle size and chemical composition (ash content, pH of the point of zero charge, FT-IR and thermal analysis). Next, the kinetic and equilibrium aspects of the adsorption of Cr(VI) by this adsorbent were studied. The kinetic data were satisfactorily fitted to a kinetic law of partial order in C equal to one. The specific adsorption rates are around 10(-4)s(-1), increasing as temperature does. A noticeable influence of diffusion on the global adsorption process has been demonstrated. Finally, the equilibrium isotherms were satisfactorily fitted to a previously proposed model. The adsorption capacity of Cr(VI) was similar to some other previously reported and the affinity of Cr(VI) towards the active sites of the adsorbent increases as temperature rises.

Comparative valorisation of agricultural and industrial biowastes by combustion and pyrolysis

Combustion and pyrolysis processes were assessed and compared for two types of lignocellulosic biowastes: agricultural (Eucalyptus bark, grape seeds, peach stones, walnut shells, olive waste and peanut shells) and industrial (primary and biological paper mill sludge) biowastes. They were characterized by elemental, proximate and thermal analyses; the pyrolysis behaviour was studied by thermogravimetric analysis and the gases produced were identified using mass spectrometry. Agricultural biowastes showed the highest calorific values, close to the fossil fuel values (20-30MJkg(-1)) and, in general, emission of gases containing the carbon element (CH4, C2H2, CO and CO2) was higher than that of the tested industrial biowastes, making the agricultural biowastes highly competitive for combustion applications such as gas fuel. Further, the solid product which resulted from the pyrolysis of industrial biowastes is a material with large specific surface area, which is a good characteristic for possible applications as adsorbent in water remediation.

Influence of the operation conditions on CO2 capture by CaO-derived sorbents prepared from synthetic CaCO3

In this work, a statistical experimental design is performed in order to prepare CaCO3 materials for use as CaO-based CO2 sorbent precursors. The influence of different operational parameters such as synthesis temperature (ST), stirring rate (SR) and surfactant percent (SP) on CO2 capture is studied by applying Response Surface Methodology (RSM). The samples were characterized using different analytical techniques including X-ray diffraction, N2 adsorption isotherm analysis and Scanning Electron Microscopy-X-ray Energy Dispersive Spectroscopy (SEM-EDX). CO2 capture capacity was determined by means of a thermogravimetric analyzer which recorded the mass uptake of the samples when these were exposed to a gas stream containing diluted (15%) CO2. The statistical approach used in this work provides a rapid way of predicting and optimizing the main preparation variables of CaO-derived sorbents for CO2 sorption. The results obtained clearly indicate that four parameters statistically influence CO2 uptake: SR, the square of SR, its interaction with SP and the square of SP.

Advanced photochemical oxidation of emergent micropollutants: Carbamazepine

The combination of UV radiation with hydrogen peroxide has been widely used for the photodegradation of pollutants in aqueous solutions. Statistical design of experiments is a powerful tool to optimize this kind of process. Initial hydrogen peroxide concentration, pH and temperature were considered as the variables for the process optimization. The interactions existing between these three variables were analyzed. Initial concentration of hydrogen peroxide proved to be the most important variable conditioning the removal efficiency, followed by temperature, and pH shows a non-significant positive influence along the whole operation interval. The ANOVA test reported significance for five of the nine involved variables. The Response Surface Methodology technique was used to optimize carbamazepine degradation. Under optimal conditions (hydrogen peroxide concentration = 0.38·10−3 mol L−1, pH = 1 and temperature = 35.6°C) total carbamazepine degradation was achieved.

Feasibility of electrochemical degradation of pharmaceutical pollutants in different aqueous matrices: Optimization through design of experiments

Electrochemical degradation of different effluents polluted with carbamazepine, a well-known refractory pharmaceutical contaminant, was addressed in this article. Ultrapure water (Milli-QTM technology), surface water from a lake and urban wastewater were the matrices used to evaluate the feasibility of performing the electro-oxidation of carbamazepine. Specific designs of experiments were planned for each of the aqueous media. The initial carbamazepine concentration and the electric current density were considered as the operational variables. Although the optimal values of both variables follow the same trend in the three cases, significant differences are observed regarding the comparative influence of each variable on the degradation of carbamazepine.

Use of cork agglomerates as acoustic absorbents

Abstract Black agglomerate (BA) and composite agglomerate (CA) of cork were tested as acoustic absorbents. The energy absorption coefficient was studied as a function of the specimen thickness. For CA, the effects on the acoustic absorption of the particle size and the resin dosage used in its preparation were also analysed. The wave ratio n, the coefficient of acoustic absorption α and the coefficient of noise reduction (CNR) were calculated using an ASTM norm (C-384-56). Usually, regardless of the specimen thickness, for both BA and CA, α first increased with frequency and then decreased. The maximum of α shifted to a higher frequency with decreasing specimen thickness. In general, BA was the best acoustic absorbent at low and high frequencies, whereas CA was at intermediate frequencies. Particle size and resin dosage had a less important influence on the absorbent behaviour of CA.

Preparation of Micropore-Containing Adsorbents from Kenaf Fibers and Their Use in Mercury Removal from Aqueous Solution

Here, a number of activated carbon fibers (ACFs) prepared from kenaf natural fibers (KNFs) by chemical activation with KOH under different operation conditions have been used as adsorbents for the removal of mercury from aqueous solutions. Samples were characterized by N2 adsorption at 77 K, mercury porosimetry, scanning electronic microscopy (SEM), and FT-IR spectroscopy. The adsorption of mercury at 25°C without pH adjustment from an aqueous solution was evaluated from both kinetic and equilibrium standpoints. It was found that the activation conditions during the preparation of ACFs (i.e., impregnation ratios and activation temperatures) had a strong influence on the porosity of the resultant samples and, therefore, on their mercury adsorption capacity. The sample prepared at 800°C using an impregnation ratio of 3:1 (named K3-800) presented the maximum Langmuir adsorption capacity (10.53 mg/g). This sample showed a specific surface area of 881 m2/g, a micropore volume of 0.60 cm3/g, and the highest total pore volume (2.69 cm3/g).