Removal of paracetamol on biomass-derived activated carbon: Modeling the fixed bed breakthrough curves using batch adsorption experiments

The remediation of paracetamol (PA), an emerging contaminant frequently found in wastewater treatment plants, has been studied in the low concentration range (0.3–10 mg L−1) using as adsorbent a biomass-derived activated carbon. PA uptake of up to 100 mg g−1 over the activated carbon has been obtained, with the adsorption isotherms being fairly explained by the Langmuir model. The application of Reichemberg and the Vermeulen equations to the batch kinetics experiments allowed estimating homogeneous and heterogeneous diffusion coefficients, reflecting the dependence of diffusion with the surface coverage of PA. A series of rapid small-scale column tests were carried out to determine the breakthrough curves under different operational conditions (temperature, PA concentration, flow rate, bed length). The suitability of the proposed adsorbent for the remediation of PA in fixed-bed adsorption was proven by the high PA adsorption capacity along with the fast adsorption and the reduced height of the mass transfer zone of the columns. We have demonstrated that, thanks to the use of the heterogeneous diffusion coefficient, the proposed mathematical approach for the numerical solution to the mass balance of the column provides a reliable description of the breakthrough profiles and the design parameters, being much more accurate than models based in the classical linear driving force.We gratefully thank Junta de Andalucía (P09-FQM-5156) and Spanish Ministry of Economy and Competitiveness (MINECO – Spain) (Project CTQ2012-36408) and Fondo Europeo de Desarrollo Regional (FEDER – Spain) for financial support

Simulación de curvas de ruptura para la adsorción de paracetamol a partir de datos obtenidos en estudio termodinámico y cinético

Los productos farmacéuticos considerados, en algunos casos, como contaminantes emergentes, poseen, en general, una alta estabilidad química y térmica y además son biológicamente activos. Algunos de ellos han sido detectados en aguas superficiales en niveles cercanos a los 100 µg/L. El uso generalizado de estos productos hace prever que su presencia se incremente en las corrientes de entrada de las estaciones depuradoras de aguas residuales. La adsorción de estos compuestos sobre carbón activo ofrece una alternativa para su eliminación. En este trabajo se presentan los resultados de un estudio de adsorción de paracetamol (producto farmacéutico de mayor concentración en aguas superficiales) en columna de carbón activo de origen lignocelulósico. Los parámetros característicos de adsorción, obtenidos de experimentos realizados en tanque de mezcla discontinuo, han sido utilizados para modelar el proceso de adsorción en columna, comparándose las curvas de ruptura simuladas con las obtenidas experimentalmente.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Adsorbent ability of lignin-based activated carbons for the removal of p-nitrophenol from aqueous solutions

This paper reports the p-nitrophenol (PNP) removal from aqueous solutions by adsorption onto active carbons (ACs). Nine ACs were prepared from acid-precipitated eucalyptus kraft lignin following a two-step process consisting in CO 2 partial gasification (750-850°C) after carbonization (350-800°C) in N 2 atmosphere. The amount adsorbed ranged from 1 to 4.4mmol/g, and it is related to the initial concentration of adsorbate, temperature, pH, burn off of the activated carbons, and contact time. The equilibrium results were fitted by the Temkin, Dubinin-Radushkevich, and Guggenheim-Anderson-de Boer equations. The main thermodynamic magnitudes were estimated as well, and their values indicated that the adsorption processes were spontaneous and exothermic. The kinetic study showed that the processes are of apparent second order related to the concentrations of the empty active sites on the ACs surface. The values of the effective diffusivities have been calculated and they have suggested that the internal diffusion controls the net mass transfer. The results obtained in the present work can be for the benefit of the preparation of new adsorbents, as well as the primary design of the adsorption equipment with separation or environmental purposesThe authors acknowledge the Spanish DGICYT-MEC (Project CTQ 2009-14262