Mathematical modeling of lead removal by natural hydroxyapatite from aqueous solution

Arturo Romero¹; Pablo Casanova¹; Norma Caballero¹; Magna M. Monteiro¹; Christian E. Schaerer¹

¹ Polytechnic School, National University of Asuncion

doi:10.20906/CPS/CILAMCE2017-0763

Resumo

Nowadays, environmental pollution by heavy metals is a great world concern due to its alarmingly high critical level. Heavy metals, such as: cadmium, mercury, chromium and lead are used in several industries reaching surface and underground water throughout industrial effluents and filtration to the aquifers. Lead is well known to be toxic to most forms of life and cannot be eliminated by the body, therefore a mechanism for removing the contamination is important, as a way of life protection and preventing illness. This work proposes a mathematical model for lead removal in aqueous solutions by natural hydroxyapatite (HAP), under continuous column flow conditions. We focus on capturing lead using hydroxyapatite derived from bovine bone since this material is available in the region and is a very important resource for the local economy. The adsorptive behavior of the material (HAP) is obtained from batch experiments and it is corroborated that the Langmuir model is the most adequate to represent the kinetic process of the reaction, Pb (II) - HAP. The flow of lead solution throughout the column is modeled using advection-dispersion terms, resulting in a non linear elliptic partial differential equation. In addition, the adsorption is parametrized and adjusted via laboratory experiments. The resulting equation is solved using a finite difference method. For the model validation, measurements of residual concentration after the adsorption process are performed in the laboratory and contrasted with the results of the numerical simulation of the mathematical model. It is observed that the numerical results capture adequately the laboratory experimental flow concentration measurements. In addition, comparisons between the laboratory experiments and computational results show that HAP could be considered as a promising material for remediation of lead in aqueous solution.

Palavras-chave: Lead; Contamination; Hydroxyapatite; Adsorption; Simulation; Finite Differences