RESUMO
This work shows a promising, environmentally friendly and greener alternative for the production and application of electrochemically produced Graphene Oxide (GO) for the adsorptive removal of Methylene Blue (MB) dye in an aqueous medium. During the adsorption tests, GO produced via electrochemical route reached the equilibrium in only 10 min of contact, exhibiting a percentage removal of MB over 97%. It could also be observed that the experimental data better fitted to the pseudo-second order kinetic model. By analysing the isotherms, it was verified the maximum adsorptive capacity was 500â mgâ g-1 (303.15â K) and that in overall, adsorptive capacity decreases with the increase in temperature. Experimental equilibrium data were better fitted to the Freundlich isotherms in all temperatures studied (303.15, 318.15 and 333.15â K). The thermodynamic analysis confirmed the exothermic nature of the process, and that MB adsorption onto GO occurs spontaneously. ΔH⦠and ΔG⦠values suggested that physisorption occurred, which is mainly due to π-π interactions and electrostatic interactions between MB and oxygen functional groups on the GO surface. Cost-effectiveness analysis showed there is a lower cost involved in the production of electrochemical GO, as compared to the Hummers method; and in the reusability study, even after 5 cycles GO removed ≥ 90% MB. Thus, the electrochemically produced GO seems to be an efficient, cost-effective and environmentally friendly alternative for colour removal from water, as it uses less hazardous and expensive reagents when compared to those applied in the traditional GO synthesis, without losing, however, the efficiency in colour removal from water.
Assuntos
Corantes , Poluentes Químicos da Água , Adsorção , Grafite , ÁguaRESUMO
It was the aim of this work to evaluate the adsorptive performance of the biochar obtained from the gasification of wood residues onto a solution of Indosol Black NF1200 dye. The study was performed by means of factorial design 22, having as control variables: pH and adsorbent's granulometry. Batch tests were carried out at 200 rpm for 3 h (T = 28 °C). As output variable, the percentage removal of dye was determined. The best operating conditions were pH = 2 and 100 mesh granulometry. Also, adsorbent dosage studies were carried out, as well as equilibrium and adsorption kinetics. Both kinetics and equilibrium of adsorption tests were proceeded in basic and acid medium. For a basic pH value (pH = 12), it was concluded the equilibrium was reached in about 3 h of experiment, the experimental qmax value was near 12 mg g-1, and the equilibrium data fitted the Langmuir model. On the other hand, for tests with pH = 2, the equilibrium was reached after 5 min of experiment, the experimental qmax value was over 185 mg g-1, and the equilibrium data fitted both the Langmuir and Freundlich models. Thus, the biochar produced via gasification of wood wastes appears to be a promising adsorbent for the removal of azo dyes from textile wastewater, especially when working at lower pH values. Also, for a 10-kg/h consumption of wood residue, approximately 10 kW of energy is generated and 1 kg of biochar is produced, which represents another advantage from the environmentally friendly point of view. Graphical abstract.