Efficient Ethanol Recovery from Yeast Fermentation Broth with Integrated Distillation–Membrane Process

A hybrid process integrating vapor stripping with vapor compression and vapor permeation membrane separation, termed Membrane Assisted Vapor Stripping (MAVS), was evaluated for recovery and dehydration of ethanol from aqueous solution as an alternative to conventional distillation–molecular sieve processes. Ethanol removal/drying performance of the MAVS system with binary ethanol–water mixtures and a yeast fermentation broth were evaluated and the fate of secondary fermentation products in the system was assessed. Simple alcohols, esters, and organic acids displayed varying degrees of recovery in the vapor stripping based on the relative vapor–liquid partitioning of the compounds. All volatilized organic compounds were concentrated to the same degree in the membrane step. Membrane permeance, permselectivity, and overall energy usage of the hybrid process were the same with the fermentation broth as with binary ethanol–water solutions. The MAVS system required less than half the energy of a distillation–molecular sieve system

EFFECTS FROM FILTRATION, CAPPING AGENTS, AND PRESENCE/ABSENCE OF FOOD ON THE TOXICITY OF SILVER NANOPARTICLES TO \u3ci\u3eDAPHNIA MAGNA\u3c/i\u3e

Relatively little is known about the behavior and toxicity of nanoparticles in the environment. Objectives of work presented here include establishing the toxicity of a variety of silver nanoparticles (AgNPs) to Daphnia magna neonates, assessing the applicability of a commonly used bioassay for testing AgNPs, and determining the advantages and disadvantages of multiple characterization techniques for AgNPs in simple aquatic systems. Daphnia magna were exposed to a silver nitrate solution and AgNPs suspensions including commercially available AgNPs (uncoated and coated), and laboratory-synthesized AgNPs (coated with coffee or citrate). The nanoparticle suspensions were analyzed for silver concentration (microwave acid digestions), size (dynamic light scattering and electron microscopy), shape (electron microscopy), surface charge (zeta potentiometer), and chemical speciation (X-ray absorption spectroscopy, X-ray diffraction). Toxicities of filtered (100 nm) versus unfiltered suspensions were compared. Additionally, effects from addition of food were examined. Stock suspensions were prepared by adding AgNPs to moderately hard reconstituted water, which were then diluted and used straight or after filtration with 100-nm filters. All nanoparticle exposure suspensions, at every time interval, were digested via microwave digester and analyzed by inductively coupled argon plasma–optical emission spectroscopy or graphite furnace– atomic absorption spectroscopy. Dose–response curves were generated and median lethal concentration (LC50) values calculated. The LC50 values for the unfiltered particles were (in μ/L): 1.1±0.1-AgNO3; 1.0±0.1-coffee coated; 1.1±0.2-citrate coated; 16.7±2.4 Sigma Aldrich Ag-nanoparticles (SA) uncoated; 31.5±8.1 SA coated. LC50 values for the filtered particles were (in μ/L): 0.7±0.1- AgNO3; 1.4±0.1-SA uncoated; 4.4±1.4-SA coated. The LC50 resulting from the addition of food was 176.4±25.5-SA coated. Recommendations presented in this study include AgNP handling methods, effects from sample preparation, and advantages/ disadvantages of different nanoparticle characterization techniques