Of the lead ions bioaccumulation process by living aquatic macrophytes Salvinia auriculata

Neste trabalho foi realizado um estudo do processo de bioacumulaÃÃo de Pb+2 pela macrÃfita aquÃtica Salvinia auriculata. Realizaram-se inicialmente testes toxicolÃgicos e de crescimento para determinar os nÃveis tÃxicos de Ãons de Pb+2, estipular a massa mÃnima adequada, duraÃÃo da experiÃncia e os intervalos de coleta para o experimento da bioacumulaÃÃo. O experimento da bioacumulaÃÃo foi conduzido utilizando plantas jovens e sadias da espÃcie aquÃtica e flutuante S. auriculata. Foram cultivadas, durante 29 dias em estufa, aproximadamente 30 gramas em recipiente de 8 L, em vÃrias rÃplicas, contendo 5 litros de uma soluÃÃo hidropÃnica (de Clark) e uma concentraÃÃo nÃo tÃxica de 2 mg Pb+2 L-1. Foram realizadas 7 coletas, incluindo a coleta 0, a intervalos de 1, 2, 5, 8, 22 e 29 dias, monitorando pH e temperatura e fazendo a reposiÃÃo de Ãgua devido a perdas por evaporaÃÃo. As concentraÃÃes totais de chumbo, tanto na fase fluida como na raiz e na folha, foram determinadas pela tÃcnica SR-TXRF. O fator de remoÃÃo de chumbo pela salvinia apÃs 29 dias de cultivo, nas condiÃÃes estudadas, foi de 87 %. AlÃm disso, foi observado que a adsorÃÃo de chumbo foi rÃpida nas primeiras 24 horas, reduzindo em aproximadamente 50 %. A partir do segundo dia, a concentraÃÃo de chumbo à quase constante, indicando a ocorrÃncia de transporte e acumulaÃÃo de chumbo na folha. Os dados experimentais de adsorÃÃo de Ãons de Pb+2 pela S. auriculata foram representados pelo modelo cinÃtico irreversÃvel de Langmuir. No ajuste dos dados experimentais pelo modelo proposto, utilizou-se de uma funÃÃo objetivo para otimizar os parÃmetros de adsorÃÃo: a constante da taxa de adsorÃÃo e a quantidade mÃxima de sÃtios disponÃveis na biomassa, cujos valores obtidos foram k = 0,12 L d mg-1 Pb+2 e qmax = 0,15 mg Pb+2 g-1. A planta S. auriculata mostrou-se uma boa opÃÃo para tratamento de efluentes atravÃs dos mecanismos de adsorÃÃo e bioacumulaÃÃo. O processo de remoÃÃo de metal por planta aquÃtica comprovou ser economicamente atrativo, de fÃcil disponibilidade, baixos custos operacionais e alta eficiÃncia.In this work was carried out a study of the lead bioaccumulation process by living aquatic macrophytes Salvinia auriculata. Initially, they were performed toxicological and growing tests in order to determine the non-toxic lead concentration limits and the minimum amount of biomass for the lead uptake experiment duration. The bioaccumulation experiment was performed using young and healthy floating aquatic plants of species S. auriculata. Approximately 30 grams of S. auriculata were put in growing at several 8-L recipients containing 5 L hydroponics solution and a non-toxic lead concentration of 2 mg L-1, during 29 days in a greenhouse. For the lead uptake experiment, seven collection times were set up at intervals of 1, 2, 5, 8, 22 and 29 days, including the zero time and was measured the growing solution temperature and pH, and the solution volume was monitored and deionized water was added to compensate the losses by evaporation. In order to measure the total lead concentration accumulated in aqueous solution obtaining from roots and leaves and growing solution, a Synchrotron Radiation Total Reflection X-Ray Fluorescence technique was used. The lead removal factor by S. auriculata after 29 days, in experimental conditions, was around 87 %. Moreover, it was observed a strong reduction of 50 % of lead concentration in liquid phase and lead accumulation in roots after the first 24 hours of experiment, while there a constant lead concentration in roots after the second day, indicating the transport and accumulation of lead into the leaves. The lead adsorption experimental data by S. auriculata were modeling by the irreversible adsorption kinetic of Langmuir. In the model, the equation system was resolved by DASSL algorithm and the kinetic parameters were obtained and optimized by an objective function using a SIMPLEX algorithm. The adsorption rate constant (k) value was 0.12 L d mg-1 Pb+2 while the maximum lead contents (qmax) value in the biomass was 0.15 mg Pb+2 g-1. The aquatic plant S. auriculata can be a good alternative for effluent treatment through both bioadsorption and bioaccumulation mechanism. The process based on the Phytoremediation technique using aquatic plants have become a attractive economical process due to its easy applicability , low operational costs and high efficiency