A novel combined airlift loop fluidized bed reactor was proposed in this work. The internal and external loops were combined and the hydrodynamic parameters like minimum fluidization velocity and liquid holdup were studied for Newtonian and non-Newtonian fluids. Studies were conducted using Newtonian fluids of water, n-butanol, 60% and 80% glycerol and non - Newtonian fluids such as 0.25%, 0.6% and 1.0% Carboxy Methyl Cellulose (CMC) aqueous solutions were employed in the liquid phases. Spheres, Bearl saddle and Raschig ring with different sizes were used as solid phase. The experimental results indicated that the increase in particle size and sphericity increased minimum fluidization velocity whereas increase in superficial gas velocity decreased minimum fluidization velocity. In addition, the liquid holdup increased with increase in particle size and superficial liquid velocity. Furthermore, an increase in superficial gas velocity decreased the liquid holdup for Newtonian and non-Newtonian systems. Two separate correlations were developed to predict the minimum fluidization velocity and liquid holdup based on the experimental results for both Newtonian and non-Newtonian liquids for a wide range of operating conditions. The capability of the proposed correlation for minimum fluidization velocity and liquid holdup was examined and reasonable agreement between predicted and experimental results of Newtonian and non-Newtonian liquids suggested the applicability of the proposed correlations.

The rapid growth of information technology and industrialization are the key components for the development of electronic equipment, and their inevitable role in human day-to-day life has an important stint in the generation of electronic waste (e-waste). This waste has far-reaching environmental and health consequences. One such e-waste printed circuit board (PCB) contains significant amounts of valuable heavy metals such as copper (Cu), lead (Pb), zinc (Zn), nickel (Ni), and others that can be extracted through various metallurgical routes. Recovery and recycle of heavy metal ions is a major challenge to prevent environmental contamination. The present study discusses the current e-waste scenario, health impacts and treatment methods in detail, and also presents experimental results of recovery of heavy metals from printed circuit boards (PCBs) by leaching using aqua regia (HCI + HNO3 and HCI + H2SO4). Under varying conditions such as specified conditions of 80°C, 0.05 mm of thickness, 3 hrs of contacttime, 80rpm shaking speed, and concentration of PCB sample of 0.5 g ml−1, it results in the composition of extracted heavy metal ions in such a way that 97.59% of copper, 96.59% of lead, 94.66% of tin, and 96.64% of zinc, respectively. The recovery of heavy metal ions from PCBs has an important leading contribution in electronic waste management and the result shows a higher rate.

Many experiments have been conducted to study the hydrodynamic characteristics of column reactors and loop reactors. In this present work, a novel combined loop airlift fluidized bed reactor was developed to study the effect of superficial gas and liquid velocities, particle diameter, fluid properties on gas holdup by using Newtonian and non-Newtonian liquids. Compressed air was used as gas phase. Water, 5% n-butanol, various concentrations of glycerol (60 and 80%) were used as Newtonian liquids, and different concentrations of carboxy methyl cellulose aqueous solutions (0.25, 0.6 and 1.0%) were used as non-Newtonian liquids. Different sizes of spheres, Bearl saddles and Raschig rings were used as solid phases. From the experimental results, it was found that the increase in superficial gas velocity increases the gas holdup, but it decreases with increase in superficial liquid velocity and viscosity of liquids. Based on the experimental results a correlation was developed to predict the gas hold-up for Newtonian and non-Newtonian liquids for a wide range of operating conditions at a homogeneous flow regime where the superficial gas velocity is approximately less than 5 cm/s.

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The effect of superficial gas and liquid velocities, particle diameter and sphericity, physical and rheological properties of liquids on gas holdup were studied in a three phase internal loop airlift fluidized bed reactor. Air was used as a gas phase. Water, n-butanol, various concentrations of glycerol (60% and 80%) were used as Newtonian liquids and different concentrations (0.25%, 0.6% and 1.0%) of carboxy methyl cellulose (CMC) solutions were used as non-Newtonian liquids. Spheres, Bearl saddle and Rasich ring with different diameters were used as solid phases. Superficial gas velocity varied from 0.000142 m/s to 0.005662 m/s and superficial liquid velocity varied from 0.001 to 0.12 m/s. The experimental result shows that increase in particle size and superficial gas velocity increases gas holdup and decreases with increase in concentration of Newtonian and non-Newtonian systems. Based on the experimental results a separate correlation was developed to predict gas holdup for both Newtonian and non-Newtonian liquids for wide range of operating conditions.