Updates on the pretreatment of lignocellulosic feedstocks for bioenergy production–a review

Lignocellulosic biomass is the most abundant renewable energy bioresources available today. Due to its recalcitrant structure, lignocellulosic feedstocks cannot be directly converted into fermentable sugars. Thus, an additional step known as the pretreatment is needed for efficient enzyme hydrolysis for the release of sugars. Various pretreatment technologies have been developed and examined for different biomass feedstocks. One of the major concerns of pretreatments is the degradation of sugars and formation of inhibitors during pretreatment. The inhibitor formation affects in the following steps after pretreatments such as enzymatic hydrolysis and fermentation for the release of different bioenergy products. The sugar degradation and formation of inhibitors depend on the types and conditions of pretreatment and types of biomass. This review covers the structure of lignocellulose, followed by the factors affecting pretreatment and challenges of pretreatment. This review further discusses diverse types of pretreatment technologies and different applications of pretreatment for producing biogas, biohydrogen, ethanol, and butanol

Artificial neural network–genetic algorithm-based optimization of biodiesel production from Simarouba glauca

A transesterification reaction was carried out employing an oil of paradise kernel (Simarouba glauca), a non-edible source for producing Simarouba glauca methyl ester (SGME) or biodiesel. In this study, the effects of three variables – reaction temperature, oil-to-alcohol ratio and reaction time – were studied and optimized using response surface methodology (RSM) and an artificial neural network (ANN) on the free fatty acid (FFA) level. Formation of methyl esters due to a reduction in FFA was observed in gas chromatography–mass spectroscopy (GC–MS) analysis. It was inferred that optimum conditions such as an oil-to-alcohol ratio of 1:6.22, temperature of 67.25 and duration of 20 h produce a better yield of biodiesel with FFA of 0.765 ± 0.92%. The fuel properties of paradise oil meet the requirements for biodiesel, by Indian standards. The results indicate that the model is in substantial agreement with current research, and simarouba oil can be considered a potential oil source for biodiesel production

Analysis of Mass Transfer Resistance for Adsorption of Phosphate onto Industrial Waste Materials in Plug-flow column

The understanding resistance of mass transfer for adsorption of phosphate (PO43-) onto industrial waste such as clay brick and ceramic as an adsorbent is important to verify. This study presented the removal of (PO43-) from a synthetic solution by adsorbing onto the clay brick and ceramic wastes in a plug flow column (PFC). The experimental results showed that increasing the flow rate was decreases the breakthrough time. The mass transfer factor (MTF) models were used to study the behaviours of breakthrough curve and to determine the resistance of mass transfer. The MTF models verified that the resistance of mass transfer could be dependent on porous diffusion until the percentage of outflow reaches 72% for clay brick waste and 86% for ceramic waste, even though film mass transfer can play a minor role in controlling the movement of (PO43-) from the bulk water to film zone. The results of MTF models coefficient could be indicated to increase the capacity of clay brick and ceramic wastes to adsorb (PO43-) from synthetic solution, it needs to develop the porosity of these adsorbents by either physical or chemical modification

Predicting the capability of carboxylated cellulose nanowhiskers for the remediation of copper from water using response surface methodology (RSM) and artificial neural network (ANN) models

This study observed the influence of temperature, initial Cu(II) ion concentration, and sorbent dosage on the Cu(II) removal from the water matrix using surface-oxidized cellulose nanowhiskers (CNWs) bearing carboxylate functionalities. In addition, this study focused on the actual conditions in a wastewater treatment plant. Conductometric titration of CNWs suspensions showed a surface charge of 54 and 410 mmol/kg for the unmodified and modified CNWs, respectively, which indicated that the modified CNWs provide a relatively high surface area per unit mass than the unmodified CNWs. In addition, the stability of the modified CNWs was tested under different conditions and proved that the functional groups were permanent and not degraded. Response surface methodology (RSM) and artificial neural network (ANN) models were employed in order to optimize the system and to create a predictive model to evaluate the Cu(II) removal performance of the modified CNWs. The performance of the ANN and RSM models were statistically evaluated in terms of the coefficient of determination (R2), absolute average deviation (AAD), and the root mean squared error (RMSE) on predicted experiment outcomes. Moreover, to confirm the model suitability, unseen experiments were conducted for 14 new trials not belonging to the training data set and located both inside and outside of the training set boundaries. Result showed that the ANN model (R2 = 0.9925, AAD = 1.15%, RMSE = 1.66) outperformed the RSM model (R2 = 0.9541, AAD = 7.07%, RMSE = 3.99) in terms of the R2, AAD, and RMSE when predicting the Cu(II) removal and is thus more reliable. The Langmuir and Freundlich isotherm models were applied to the equilibrium data and the results revealed that Langmuir isotherm (R2 = 0.9998) had better correlation than the Freundlich isotherm (R2 = 0.9461). Experimental data were also tested in terms of kinetics studies using pseudo-first order and pseudo-second order kinetic models. The results showed that the pseudo-second-order model accurately described the kinetics of adsorption

Competitive biosorption of Cr(<scp>vi</scp>) and Zn(<scp>ii</scp>) ions in single- and binary-metal systems onto a biodiesel waste residue using batch and fixed-bed column studies

A feasible biosorption process for the removal of Cr(vi) and Zn(ii) ions from single and binary solutions onto a defatted pongamia oil cake (DPOC) was investigated.</p