Production of granular activated carbon based materials obtained from macauba endocarp waste and iron mining for environmental remediation

The generation of industrial waste and the contamination of water resources by different contaminants (e.g. organic compounds, heavy metals and phosphate) characterize environmental problems that are extensively studied. In this work, it was used two kind of waste obtained in large scale from different industrial processes: (i) macauba endocarp, a residual biomass obtained from the fruit oil extraction process, highly exploited in biofuel production, and (ii) waste from iron mining, generated in large quantities and currently stored in dams, a dangerous arrangement that has resulting in several environmental disasters in recent years. The endocarp of the macauba palm was used in the synthesis of granular activated carbon with mesopores (CAG) and later, this granular activated carbon was used as a base in the synthesis of materials with modified surfaces, as well as for synthesis of iron/carbon (C/Fe) composites, using the iron mining tailings as iron source with the purpose of adding value and giving a technological application to these materials. The prepared materials were used in the removal of different contaminants from aqueous media: organic contaminants, such as emerging contaminants, heavy metals and phosphate. CAG developed using macauba endocarp was characterized by different techniques and presented high surface area, large micropores and narrow mesoporous. Its maximum adsorption capacity in relation to the three main studied emerging contaminants (bisphenol A, ethinylestradiol and amoxicillin) is much higher than that obtained with the reference adsorbents (0.148 0.104 and 0.072 mmol g^-1 , respectively). Furthermore, the influence of temperature and pH in the adsorption process allowed a description of the adsorption mechanism. Adsorption of trace elements Zn, Cd and Pb was performed using CAG after surface modification using different methods for surface modification of the material. The adsorbents were obtained in granular form, which facilitates all stages of use, recovery and reuse of the material, unlike the powdered activated carbon normally used. The materials were characterized using different techniques that confirmed the functionalization of the carbon surface. The materials presented high metal adsorption capacity when compared to other works in the literature and high reusability after four cycles. Finally, different C/Fe based composites were obtained by manual grinding followed by thermal treatment at 300, 500 and 800 °C under nitrogen atmosphere. The effects of the thermal treatment were analyzed by Mössbauer spectroscopy and X-ray diffraction and showed that the increase of the treatment temperature promoted the formation of different reduced iron phases. These composites were used in a combined adsorption/oxidation by photocatalysis process that was able to remove up to 93% of amoxicillin from the aqueous phase. This removal was achieved by a synergistic effect of activated charcoal and reduced iron phases. The formation of possible reaction intermediates was monitored by electrospray ionization mass spectrometry (ESI-MS) and an amoxicillin degradation mechanism was proposed. Subsequently, the composites were conducted to evaluate the impact of various parameters on phosphate adsorption processes, including reaction time, temperature and pH, and showed a maximum adsorption capacity of 40.3 mg g-1 . The adsorption capacity obtained for all materials was higher than those found in the literature. (author)