No abstract

A microsphere synthesized by emulsion crosslinking of polyethylenimine (PEI) was applied in the removal of ionic dyes from water. Firstly, the stability of the PEI solution-in-liquid paraffin emulsion was improved by using the mixture of Span-80/Tween-80 as the emulsifier. The optimization by 2 5-1 fractional factorial design demonstrated the most stable emulsion was prepared at 0.07 g/mL of the emulsifier dosage, 6:4 (v:v) of the oil/water ratio, 20 % (wt %) of the PEI concentration, 6:1 (w:w) of the Span-80/Tween-80 ratio with a homogenization speed of 6000 r/min for 3 min at 25 o C. Then, the polyamine microsphere (PA-M) was obtained by crosslinking the PEI emulsion with glutaraldehyde. The PA-M microsphere can adsorb xylenol orange (XO) from aqueous solution with a capacity of 1169.2±12.5 mg/g. The amount of XO adsorption remained constant in the pH range of 2.0-11.0. Adsorption kinetics analysis demonstrated that Pseudo first-order model fit the experimental data better, indicating the overall adsorption process was controlled by 'surface reaction'. The XO adsorption on the microsphere was due to an electrostatic interaction according to the results of ΔG evaluation. The value of separation factor suggested the XO adsorption was favorable. The used PA-M microsphere can be regenerated and reused in adsorption/desorption operation at least 20 times.

Support-free cross-linked polyethyleneimine sorbent (CPEI) for CO2 capture was evaluated as the regenerable sorbent. The total amines available for the CO2 capture on CPEI were determined by the polyethyleneimine/glutaraldehyde ratio for the synthesis of CPEI. The CO2 capacity of CPEI in the slurry bubble column reactor reached 4.92 mmol/g, which is 1.97 times higher than that obtained under anhydrous conditions. The adsorption kinetics of CPEI in the reactor were investigated in terms of the CPEI amount, the CO2 fraction, the gas flow rate, temperature, and the total amines available. The experimental breakthrough curves for the sorbent were well-fitted with a fractional-order kinetic model. The modeling analysis found the influence of diffusion resistance on the adsorption is more significant than that of the driving force. The CO2 capacity of CPEI remained almost constant during the temperature swing adsorption/desorption cycles.