Preparation of carbonaceous materials from flotation-sludge of the poultry industry and its application in the methylene blue adsorption.

In this work, different carbonaceous materials based on floated sludge from a poultry industry wastewater treatment plant (PI-WTP) were synthesized. These materials were characterized and investigated in methylene blue dye (MB) adsorption. The influences of the initial pH solution, adsorbent dosage, kinetics, equilibrium, and thermodynamics were evaluated in the adsorption experiments. A simulation of a real textile effluent was also carried out to evaluate the adsorbent. The results of the adsorbents' characterization demonstrated that adding ZnCl2 + lime, followed by pyrolysis and acid leaching, significantly improved the material's properties, leading to abundant porosity and high surface area. The adsorption experiments indicated that the natural pH of the solution (8.0) and the AC-II dosage of 0.75 g L-1 are optimal for MB removal. Elovich and Sips' models (with a maximum adsorption capacity of 221.02 mg g-1 at 328 K) best fitted the experimental kinetic and equilibrium data, respectively. The adsorption process is spontaneous and endothermic according to thermodynamic parameters. The discoloration efficiency of the simulated effluent was 67.8%. In conclusion, the floated sludge, a residue produced on a large scale that needs to be disposed of correctly, can be converted into a value-added material (carbonaceous adsorbent) and applied to treat colored effluents.

Citrus fruit residues as alternative precursors to developing H2O and CO2 activated carbons and its application for Cu(II) adsorption.

Due to its toxicity, the presence of Cu(II) ions released in aquatic environments presents a serious threat to the environment and human health. In search of sustainable and low-cost alternatives, there are citrus fruit residues, which are generated in large quantities by the juice industries and can be used to produce activated carbons. Therefore, the physical route was investigated for producing activated carbons to reuse citrus wastes. In this work, eight activated carbons were developed, varying the precursor (orange peel-OP, mandarine peel-MP, rangpur lime peel-RLP, and sweet lime peel-SLP) and the activating agent (CO2 and H2O) to remove Cu(II) ions of the aqueous medium. Results revealed promising activated carbons with a micro-mesoporous structure, a specific surface area of around 400 m2 g-1, and a pore volume of around 0.25 cm3 g-1. In addition, Cu (II) adsorption was favored at pH 5.5. The kinetic study showed that the equilibrium was reached within 60 min removing about 80% of Cu(II) ions. The Sips model was the most suitable for the equilibrium data, providing maximum adsorption capacities (qmS) values of 69.69, 70.27, 88.04, 67.83 mg g-1 for activated carbons (AC-CO2) from OP, MP, RLP, and SLP, respectively. The thermodynamic behavior showed that the adsorption process of Cu(II) ions was spontaneous, favorable, and endothermic. It was suggested that the mechanism was controlled by surface complexation and Cu2+-π interaction. Desorption was possible with an HCl solution (0.5 mol L-1). From the results obtained in this work, it is possible to infer that citrus residues could be successfully converted into efficient adsorbents to remove Cu(II) ions from aqueous solutions.

Pyrolysis of citrus wastes for the simultaneous production of adsorbents for Cu(II), H2, and d-limonene.

A route based on pyrolysis and physical activation with H2O and CO2 was proposed to reuse citrus waste traditionally discarded. The citrus wastes were orange peel (OP), mandarine peel (MP), rangpur lime peel (RLP), and sweet lime peel (SLP). The main aim was to use the solid products of this new route as adsorbents for Cu(II) ions. Copper ions are among the most important water pollutants due to their non-degradability, toxicity, and bioaccumulation, facilitating their inclusion and long persistence in the food chain. Besides the solid products, the liquid and gaseous fractions were evaluated for possible applications. Results showed that the citrus waste composition favored the thermochemical treatment. In addition, the following yields were obtained from the pyrolysis process: approximately 30 % wt. of biochar, 40 % wt. of non-condensable gases, and 30 % wt. of bio-oil. The biochars did not present a high specific surface area. Nevertheless, activated carbons with CO2 and H2O presented specific surface areas of 212.4 m2/g and 399.4 m2/g, respectively, and reached Cu(II) adsorption capacities of 28.2 mg g-1 and 27.8 mg g-1. The adsorption kinetic study revealed that the equilibrium was attained at 60 min and the pseudo-second-order model presented a better fit to the experimental data. The main generated gases were CO2, which could be employed as an activating agent for activated carbon production. d-limonene, used for food and medicinal purposes, was the main constituent of the bio-oil.

Adsorption of ibuprofen, ketoprofen, and paracetamol onto activated carbon prepared from effluent treatment plant sludge of the beverage industry.

The presence of emerging contaminants such as pharmaceuticals in aquatic means presents as a serious threat, since their real consequences for the environment and human health are not well known. Therefore, this work consisted of preparing and characterize sludge-derived activated carbons (beverage sludge activated carbon - BSAC and acid-treated beverage sludge activated carbon - ABSAC) to investigate their use in the pharmaceuticals adsorption in aqueous media. The morphology study has demonstrated that ABSAC, unlike BSAC, exhibited an abundant porous structure, with smaller particles and bigger roughness. Adsorption results indicated that the ABSAC was more effective that BSAC, since it presented superior surface area (642 m2 g-1) and total pore volume (0.485 cm3 g-1) values. Pseudo-second-order kinetic model was more suitable to predict experimental data. Sips model best described the equilibrium data, with maximum adsorption capacities of 145, 105, and 57 mg g-1 for paracetamol, ibuprofen, and ketoprofen, respectively. Besides, the sludge-derived adsorbent was highly efficient in the treatment of a simulated drug effluent, removing 85.16% of the pharmaceutical compounds. Therefore, the material prepared in this work possesses intrinsic characteristics that make it a remarkable adsorbent to be applied in the treatment of pharmaceutical contaminants contained in industrial wastewater.

Simultaneous production of mesoporous biochar and palmitic acid by pyrolysis of brewing industry wastes.

Pyrolysis of malt bagasse was carried out to obtain simultaneously a mesoporous biochar and an oil fraction rich in palmitic acid. The best result for biochar production was at 500 °C with holding time of 10 min. The yields of biochar and pyrolytic oil in this condition were, 29.7 and 33.9 wt%, respectively. The pyrolysis temperature and holding time influenced the yields of the products. An increase in pyrolysis temperature (from 500 to 700 °C) and holding time (from 10 to 50 min) caused a decrease in biochar yield, a reduction in the volatile matter content and an increase in the amount of ash. Additionally, in the range studied in this work, the increase of the pyrolysis temperature caused a decrease in the specific surface area and total pore volume of the biochar. Meanwhile, the biochar presented interesting functional groups and a mesoporous character, which can be a precursor to obtain adsorbents, or even, be used as adsorbent. The pyrolytic oil was composed of oxygenated aromatic compounds, the main fraction being palmitic acid (27.3%), which can be used in a number of applications, including biodiesel production. This work demonstrated that an available and problematic waste, malt bagasse, can be converted simultaneously into a mesoporous biochar and, into a pyrolytic oil rich in palmitic acid. Biochar and pyrolytic oil, in turn, are products of great value and can be applied in several fields.

Development of high quality activated carbon from biological sludge and its application for dyes removal from aqueous solutions.

A high quality activated carbon was developed from biological sludge of a beverage wastewater treatment plant (BWTP). The material was characterized and its adsorption potential to remove Allura Red AC and Crystal Violet dyes from aqueous media was verified. The ACBS (activated carbon from beverage sludge) revealed mesoporous features, presenting average pore diameter of 6.32 nm, pore volume of 0.5098 cm3 g-1 and surface area of 631.8 m2 g-1. Adsorption was adequate using 0.25 g L -1 of ACBS, and, the process was favored at pH 2.0 for Allura Red AC and pH 8.0 for Crystal Violet. From the kinetic viewpoint, the data were satisfactorily represented by the pseudo-second order model. Freundlich and Sips models were suitable to represent the adsorption equilibrium of the Allura Red and Crystal Violet, respectively. The maximum values for adsorption capacities were 287.1 mg g-1 for Allura Red and 640.7 mg g-1 for Crystal Violet. The adsorption of both dyes was thermodynamically spontaneous, favorable and endothermic. In brief, the residual sludge of a wastewater treatment plant may be used as an eco-friendly precursor for ACBS production. ACBS was an efficient adsorbent material able to uptake dyes from aqueous solutions.

Development of CO2 activated biochar from solid wastes of a beer industry and its application for methylene blue adsorption.

An alternative activated biochar was developed from barley malt bagasse (BMB) through pyrolysis followed by CO2 activation. The materials BMB, biochar and activated biochar (CO2-biochar) were characterized and tested as adsorbents for the removal of methylene blue (MB) from aqueous solutions. Adsorption kinetics, equilibrium and thermodynamics were studied. It was found that BMB and biochar presented surface area values lower than 1 m2 g-1, while CO2-biochar was a typical mesoporous material with surface area around 80 m2 g-1. As consequence, the adsorption potential for methylene blue was in the following order CO2-biochar ≫ biochar > BMB. Adsorption kinetics of MB on CO2-biochar followed the pseudo-second order model. Langmuir presented the best fit with the equilibrium adsorption isotherms. The maximum adsorption capacity was 161 mg g-1. MB adsorption on CO2-biochar was spontaneous, favorable and exothermic. Pyrolysis followed by CO2 activation was a suitable route to produce an alternative mesoporous adsorbent from barley malt bagasse.

CuO/ZnO coupled oxide films obtained by the electrodeposition technique and their photocatalytic activity in phenol degradation under solar irradiation.

CuO/ZnO coupled oxide films were electrodeposited onto an aluminum substrate and tested as photocatalysts in degradation of phenol molecules in aqueous solution under sunlight. The obtained films were characterized by X-ray diffraction, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results showed that the photocatalytic activity of films was significant, especially to coupled oxide film with a CuO/ZnO ratio equal to 0.697, which presented about 70% degradation of the aromatic molecules and 42% of total organic carbon (TOC) removal at 300 min under solar irradiation. Therefore, this work highlights the potential application of CuO/ZnO coupled oxide films obtained by electrodeposition onto aluminum substrate in the field of photocatalysis.