Effect of operational variables on biological hydrogen production from palm oil mill effluent by dark fermentation using response surface methodology

This work is a study of the performance and effect of operational parameters on biohydrogen production from palm oil mill effluent by dark fermentation in batch mode. The tests were conducted with samples prepared in 150 mL bottles using a shaker at 150 rpm. Response surface methodology was applied to investigate the influence of the four significant independent parameters viz. pH (5, 5.5, and 6), temperature (30°C, 35°C, and 40°C), substrate concentration (5,000, 12,500, and 20,000 mg L –1 ) and inoculum–substrate ratios of 2, 0.8, and 0.5 (expressed as volatile suspended solid (VSS) basis) with the inoculum concentration of 10 g L –1 VSS on biohydrogen production. All the experiments were analyzed at the incubation time of 8, 16, and 24 h. Upon seeing each interval, the results were compared. The highest chemical oxygen demand (COD) removal, the hydrogen content in the biogas as hydrogen percentage (H 2 %), and hydrogen yield (HY) were obtained 58.3%, 80%, and 3.63 mol H 2 mol –1 glucose, respectively, at 24 h incubation time. An overlay study was done to find an overall optimization of the parameters. The optimized conditions were COD removal 49%, HY 3.2 mol H 2 mol –1 glucose, and hydrogen percentage 80%. Also, the Monod model was studied to calculate the kinetics constants of the maximum substrate utilization rate (U max ) and half-velocity K s which are found to be 0.261 g L –1 d –1 and 0.349 mg L –1 , respectively. © 2019 Desalination Publications. All rights reserved

Novel self-assembled 3D flower-like magnesium hydroxide coated granular polyurethane: Implication of its potential application for the removal of heavy metals

Novel nanostructured three-dimensional flowerlike Mg(OH) 2 -incorporated granular polyurethane (designated as gPU-FMH) was prepared using a simple hydrothermal method, for which commercial MgO, water, and granular polyurethane (gPU) were applied. Interestingly, it is found that gPU and the hydrothermal process are the key factors for the assembly of the flowerlike structures of the Mg(OH) 2 , as its hexagonal nanosheet petals provide a high surface area. Temperature significantly controlled the morphologies of the flowerlike Mg(OH) 2 , and the granular gPU-FMH showed the superb adsorption capacities of 472, 1050, and 1293 mg g −1 (maximum adsorption capacities, q m , from Langmuir model) for Cu(II), Cd(II), and Pb(II), respectively. The proposed hypothesis for the synthesis of gPU-FMH and the removal mechanism of the heavy metals has been proved through various spectroscopic analyses. In the result of the continuous-flow column study, gPU-FMH showed a long breakthrough and a high removal capacity (184 mg g −1 ) of Cu(II). © 2018 Elsevier Lt

Evolutionary Prediction of Biohydrogen Production by Dark Fermentation

The present work is a study of the performance and effect of operational parameters on biohydrogen production from palm oil mill effluent by dark fermentation in batch mode. The process parameters examined are pH (5, 5.5, and 6), temperature (30, 35, and 40 °C), substrate concentration (5000, 12 500, and 20 000 mg L−1) and inoculum volume (20, 25, and 30 mL). The inoculum concentration prepared was 10 000 mg L−1 volatile suspended solids. The experiments were designed by response surface methodology (RSM). The highest chemical oxygen demand (COD) removal, hydrogen percentage (H2%) and hydrogen yield (HY) obtained were 58.3%, 80%, and 4.83 mol H2/mole of COD consumed, respectively. Based on the experimental data obtained with the RSM design, gene expression programming (GEP) was developed to predict the COD removal, hydrogen production, and hydrogen yield as process responses. The projected models were assessed based on the correlation coefficient (R2), root mean square error, mean absolute relative error, scatter index, and BIAS. The results demonstrate that the GEP model outperformed the RSM model and was superior in predicting the response variables. Partial derivative sensitivity analysis was also employed to assess the effect of each variable on COD%, H2%, and HY prediction. The prediction uncertainty for COD%, H2%, and HY was quantified, and the results were ±0.11, ±0.17, and 0.015, respectively. According to the results, the GEP model is more efficient than the RSM model in predicting the experimental data for biological hydrogen production in the dark fermentation process

Facile and economic one-pot synthesis of rigid functional-polyurethane for the effective treatment of heavy metal-contaminated urban storm water run-off

In this study, highly permeable rigid polyurethanes (PU) incorporating calcium oxide (CaO) (PU/CaO) composite materials were prepared via a facile and economic one-pot synthesis method and characterized for remediation of heavy metal-contaminated urban storm water run-off (USR) in a fixed-bed column. Column tests were conducted to investigate various parameters, and data were interpreted using the Bed Depth Service Time model to predict service time. Among the media tested, 25% CaO-incorporated PU (PU/CaO-25) had the highest adsorption capacity of Cu(II). PU/CaO-25 had about 2.5-fold higher rigidity (0.38 MPa) than a “typical” rigid polymer (0.15 MPa). Hydraulic conductivity tests showed PU/CaO-25 (avg. 0.4 mm) had a permeability (0.108 cm s−1) equivalent or higher than reference sands. Specific structural features of PU/CaO-25 and the remediation mechanism were also determined using FESEM/EDS, XRD, N2 gas isotherm and chemical equilibrium modeling. Moreover, column tests using simulated USR showed that all heavy metals were removed by PU/CaO-25 to below their regulation levels at ~1,100 bed volumes. Based on the physicochemical properties and functionality, PU/CaO-25 may be useful as an effective filter material in USR treatment and reuse applications