Desenvolvimento e aplicação de biossorventes no tratamento de soluções aquosas contaminadas por azul de metileno

Abstract

In recent years human society has experienced many technological advances and a significant increase in the consumption and production activities. All these activities have contributed to the production of a large volume of residues that without adequate control may compromise countless environments and ecosystems. Different actions and technologies have been developed aiming the remediation of environments contaminated by waste materials proceeding from industrial and anthropogenic activities. For instance, adsorption process has been employed efficiently in the remediation of aquatic environments contaminated by various classes of pollutants. Overall, adsorption possesses countless advantages over other remediation methods. In this sense, this Dissertation reports the synthesis of microspheres based on pectin (PB) and pectin/cellulose microfibrils (PB-CF) to be implemented as adsorbent materials for wastewater remediation. Both pectin and cellulose microfibrils were extracted from solid residues of orange fruit. As assessed, the microspheres filled with cellulose microfibrils exhibited remarkable difference regarding various properties in comparison to the PB microspheres. The adsorption capacity of PB and PB-CF was tested towards the removal of methylene blue (AM) from water. In addition, the effect of several parameters (e.g. contact time, pH and temperature) on the adsorption process was studied. As evaluated, the adsorption kinetics of AM onto both types of microspheres followed a pseudosecond order model. The experimental data regarding the amount of AM adsorbed per gram of adsorbent at equilibrium were fitted by the Langmuir isotherm model. According to this isotherm, the maximum adsorption capacity calculated to PB is 1550.3 mg/g whilst the microspheres filled with 5 w/w.% of cellulose microfibrils (PB-CF5) showed a maximum adsorption capacity of 2307.9 mg/g. Recycling and reuse experiments revealed that both PB and PBCF can be employed efficiently on the removal of AM in at least 6 consecutive adsorption/desorption cycles. Taken together, these results suggest that both PB and PB-CF can be utilized as low-cost biosorbents in the treatment of wastewater contaminated by AM. Furthermore, here it was demonstrated that agro-industrial residues are promising sources of biocompounds, which are applicable to the formulation of new materials. Overall, the data described and discussed in Dissertation contribute to the reduction of waste materials disposed in the environment and also present novel biosorbents applicable in the remediation of contaminated aquatic environments.