Biossorção de lantânio por Sargassum sp.: ensaios em batelada e contínuos

Abstract

Considering the utmost technological advances, researchers have intensified the searching for a new methodology on removing metals from wastewaters that can provide adequate outcomes as far as the metal uptake is concerned, allied with cost effectiveness of the process. The use of organic materials such as algae, fungi and bacteria has been highlighting and is becoming to be considered an interesting solution when compared to conventional chemical treatments. This technique is called biosorption, which is a process that captures metal ions from a solution, based on the interactions between metals and active groups present on the cell wall of the biomass. The interest on the application of this technique is growing and studies about the maximum concentration that can be discharged in the environment without harmful consequences and for the separation and recovery of rare-earth (RE) elements are being done. In this work, it was used the biomass Sargassum sp. as biosorbent in Lanthanum biosorption process. It was performed kinetic, equilibrium and continuous studies of biosorption of lanthanum ions (III) by means of a bimetallic continuous system, to which there was the addition of Cerium metal, another element of the RE. Analytical determinations were performed by inductively coupled plasma optical emission spectrometry. Kinetic experiments were performed at constant temperature of 30 ± 1 ° C, metal concentrations of 10 and 100 mg.L-1 and at two different concentrations of biomass 2 and 5 g.L-1. Two kinetic models were tested, pseudo-first order and second order, and a comparison of the best fit was made from the second-order model with r2 equal to 0.9697. In the equilibrium experiment the isotherm was obtained with a rising profile in the capture, without reaching the maximum removal. The Langmuir and Freundlich models were used to help to fit the data of the isotherm, being the Langmuir model the one presenting greater correlation, with a maximum uptake value of 3.55 mmol.g-1. In the dynamic test, two experiments were conducted. Test 1 was conducted with three interconnected columns filled with 20g of biomass each, pumped the Lanthanum solution. Test 2 was made from Lanthanum solution and Cerium pumped for column with 20g of biomass. The results showed that the saturation point was not achieved in the 8h of the experiment, which indicates the high affinity of Sargassum sp by Lanthanum and that the presence of Cerium as well as flow reduction impaired the uptake of Lanthanum