Rafael Teixeira Rodrigues

Comparison between coagulation-flocculation and ozone-flotation for Scenedesmus microalgal biomolecule recovery and nutrient removal from wastewater in a high-rate algal pond

The removal of nutrients by Scenedesmus sp. in a high-rate algal pond, and subsequent algal separation by coagulation-flocculation or flotation with ozone to recover biomolecules, were evaluated. Cultivation of Scenedesmus sp. in wastewater resulted in complete NH3-H removal, plus 93% total nitrogen and 61% orthophosphate removals. Ozone-flotation obtained better water quality results than coagulation-flocculation for most parameters (NH3-N, NTK, nitrate and nitrite) except orthophosphate. Ozone-flotation, also produced the highest recovery of lipids, carbohydrates and proteins which were 0.32 ± 0.03, 0.33 ± 0.025 and 0.58 ± 0.014 mg/mg of biomass, respectively. In contrast, there was a low lipid extraction of 0.21 mg of lipids/mg of biomass and 0.12-0.23 mg of protein/mg of biomass in the coagulation-flocculation process. In terms of biomolecule recovery and water quality, ozone showed better results than coagulation-flocculation.

Nucleation, growth and coalescence phenomena of air bubbles on quartz particles in different aqueous solutions

Understanding the generation and behaviour of air bubbles in the presence of different reagents is important in the solid/liquid separation processes used to treat mineral and water and wastewater by flocculation–flotation. The presence of large air bubbles in aerated flocs, which have higher up-rising rates, can lead to the development of higher capacity units. The present work evaluated the generation and behaviour of air bubbles on hydrophilic particles of quartz in water and other aqueous solutions (10 mg L−1 920SH non-ionic polymer, 30 mg L−1 DF250 surfactant and 50 mg L−1 Flotigan EDA amine). The operating parameters were the air bubble growth time, contact angle, adhesion, attachment and detachment. The main results showed that the air bubbles grew more readily in the presence of non-ionic polymers and after adhesion in non-ionic polymer and water. The formation of large bubbles in aerated flocs in an effort to develop industrial flocculation–flotation operations with higher throughputs units is di...

TÉCNICAS NO CONVENCIONALES DE FLOTACIÓN DE PARTÍCULAS FINAS DE SULFUROS DE COBRE Y MOLIBDENO.

Se presentan resultados (laboratorio y piloto) de dos tecnicas de flotacion de particulas minerales finas (menor 38 um) de sulfuros de Cu y Mo: Acondicionamiento en Alta Intensidad y flotacion extensora (extender). La eficiencia global fue superior con las tecnicas estudiadas: mayores recuperaciones de Cu y Mo, mejor cinetica y menores grados de arrastre hidrodinamico. Con la flotacion “extender” (mejores resultados), empleando aceite Diesel (mayor 60 gt-1), las recuperaciones de Cu y Mo y sus cineticas fueron 2-5 por ciento superiores al estandar. Se analizan los mecanismos y el potencial de estas tecnicas para el tratamiento avanzado de finos de minerales.