BACKGROUND Increasing demand on energy sources has motivated research studies on renewable energy originating from biomass. Water lettuce (Pistia stratiotes L.) as an invader lignocellulosic biomass with high crop yield can be utilized in anaerobic digestion to produce biomethane. Substrate and inoculum concentrations, and temperature are important parameters for kinetic analysis of methane production that was performed with water lettuce and waste sludge for the first time. Kinetic analysis can be used in reactor design, scale up and identification of optimum conditions. RESULTS In the present study, anaerobic digestion of water lettuce with waste sludge as inoculum was performed in a batch system. Substrate concentration [30, 40 and 50 g total solid (TS) L−1], waste sludge concentration (3.4 and 6.8 g TS L−1) were investigated at different digestion temperatures (35, 45, 55 and 65 °C). In the studied range, the highest biogas yield [321 mL g–1 volatile solid (VS) with 72.5% of methane content) was reached at substrate concentration of 30 g TS L−1 and waste sludge concentration of 6.8 g TS L−1 at 35 °C. The Cone model fitted well to the actual methane production compared to the modified Gompertz model. The effect of digestion temperature on methane production potential was described by the Ratkowsky model (R2 = 0.91) and optimum digestion temperature was found as 45 °C. Experimental methane yields were 81.5–232.7 mL methane g–1 VS which were 27.7–79.0% of theoretical maximum methane yield. Energy conversion efficiency was reached up to 78.4%. CONCLUSION The results revealed that anaerobic digestion of water lettuce with waste sludge for high methane production rate was accomplished at certain substrate and inoculum concentrations and temperature. © 2019 Society of Chemical Industry
Summary In this study, a strong acidic‐type cation exchange resin was used in the transesterification of corn oil to fatty acid methyl esters (FAME). The gel‐type cation exchange resin (Purolite‐PD206) was used in H+ and Na+ forms to utilize ion‐exchange resin as effective heterogeneous catalyst in the production of biodiesel. Effect of ionic forms of ion exchange resin on free fatty acid (FFA) conversion and composition was investigated by using different amounts of ion exchange resin (12, 16, and 20 wt%), various mole ratios of methanol to oil (1:6, 1:12, and 1:18 mol/mol), reaction temperatures (63, 65, and 67°C), and reaction time (24, 36, and 48 h) during transesterification reaction. The highest FFA conversions of 73.5% and 79.45% were obtained at conditions of 20 wt% of catalyst, 65°C of reaction temperature, 18:1 as methanol to oil ratio, and 48 h of reaction time for H+ and Na+ forms of ion exchange resin, respectively. These results were obtained from regression equations established by using analysis of variance (ANOVA) model according to the experimental results of selected parameters. Gas chromatography analysis revealed that FAME is mainly composed of C16:0 (palmitic), C18:1 (oleic), and C18:2 (linoleic) acids of methyl ester.
The membrane emulsification process (ME) using a metallic membrane was the first stage for preparing a spherical and monodisperse thermoresponsive molecularly imprinted polymer (TSMIP). In the second step of the preparation, after the ME process, the emulsion of monomers was then polymerized. Additionally, the synthesized TSMIP was fabricated using as a functional monomer N-isopropylacrylamide, which is thermosensitive. This special type of polymer was obtained for the recognition and determination of trace bisphenol A (BPA) in aqueous media. Two types of molecularly imprinted polymers (MIPs) were synthesized using amounts of BPA of 5 wt.% (MIP-2) and 7 wt.% (MIP-1) in the reaction mixtures. Additionally, a non-imprinted polymer (NIP) was also synthesized. Polymer MIP-2 showed thermocontrolled recognition for imprinted molecules and a higher binding capacity than its corresponding non-imprinted polymer and higher than other molecularly imprinted polymer (MIP-1). The best condition for the sorption process was at a temperature of 35 °C, that is, at a temperature close to the phase transition value for poly(N-isopropylacrylamide). Under these conditions, the highest levels of BPA removal from water were achieved and the highest adsorption capacity of MIP-2 was about 0.5 mmol g−1 (about 114.1 mg g−1) and was approximately 20% higher than for MIP-1 and NIP. It was also observed that during the kinetic studies, under these temperature conditions, MIP-2 sorbed BPA faster and with greater efficiency than its non-imprinted analogue.
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