Evaluation of the potential of coal fly ash produced by gasification as hexavalent chromium adsorbent.

The aim of this work was to characterize the coal fly ash from gasification process (G-CFA) and to analyze its potential as hexavalent chromium Cr (VI) adsorbent. The G-CFA was characterized in terms of physical, chemical, mineralogical, and morphological analyses. Bach adsorption studies were carried out in order to evaluate the influence of pH on the adsorption capacity and removal efficiency of Cr (VI). The G-CFA characterization demonstrated that the material possessed potential to be applied as an effective low-cost adsorbent, once it presents 18.82 m2 g-1, 0.036 cm3 g-1, and 7.56 nm of surface area, pore volume, and average pore diameter, respectively. The results also showed well-defined mineralogical phases and high content of siliceous material. The adsorption experiments demonstrated that the material has potential to be used as a chromium adsorbent with high removal efficiencies.

Enzymatic synthesis of ethyl esters from waste oil using mixtures of lipases in a plug-flow packed-bed continuous reactor.

This work describes the continuous synthesis of ethyl esters via enzymatic catalysis on a packed-bed continuous reactor, using mixtures of immobilized lipases (combi-lipases) of Candida antarctica (CALB), Thermomyces lanuginosus (TLL), and Rhizomucor miehei (RML). The influence of the addition of glass beads to the reactor bed, evaluation of the use of different solvents, and flow rate on reaction conditions was studied. All experiments were conducted using the best combination of lipases according to the fatty acid composition of the waste oil (combi-lipase composition: 40% of TLL, 35% of CALB, and 25% of RML) and soybean oil (combi-lipase composition: 22.5% of TLL, 50% of CALB, and 27.5% of RML). The best general reaction conditions were found to be using tert-butanol as solvent, and the flow rate of 0.08 mL min-1 . The combi-lipase reactors operating at steady state for over 30 days (720 h), kept conversion yields of ∼50%, with average productivity of 1.94 gethyl estersgsubstrate-1 h-1 , regardless of the type of oil in use. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:952-959, 2018.