•Pre-treatment methods of MSS are analyzed and the effect of different solvents on the extraction of lipids was discussed.•State-of-art of biofuel production from sewage sludge is critically ...presented.•Parametric optimization efforts for efficient biodiesel production were summarized.•Attempts on kinetics of transesterification reaction and intensification of biodiesel production were analyzed.•Quality of biodiesel and process economics were discussed.
Bio-fuels are gaining worldwide attention as an alternative fuel option replacing the usage of the mineral diesel derived from conventional fossil sources. However, the high cost attributed by the feedstock made it less competitive with the commercial diesel. A widespread research is going on worldwide for the production of fuels from renewable biomass replacing the currently used traditional sources. The high lipid-containing municipal sewage sludge (MSS) can be considered as a potential feedstock owing to its low cost and abundant availability. The lipids are transformed to biodiesel via transesterification or to bio-oil by pyrolysis. In this review paper, a comprehensive discussion on the various aspects of bio-fuel production from sludge derived lipids along with the key parameters affecting the process and its economics are presented. This review also emphasizes that future studies should focus on the usage of modern process intensification techniques for more efficient production of bio-fuel from renewable biomass.
A comparison of the linear and non-linear methods for the selection of optimum equilibrium isotherm for the adsorption of methylene blue onto the banana root (
Musa acuminata
) derived activated ...carbons was carried out. The adsorption equilibrium data were fitted to three isotherm models: Langmuir, Freundlich, and Temkin. The prediction of optimum isotherm was based on six error functions: the coefficient of determination (
R
2
), the sum of the squares of the errors (SSE), the sum of the absolute errors (SAE), the average relative error (ARE), the hybrid fractional error function (HYBRID), and the Marquardt’s percent standard deviation (MPSD). The optimum isotherm achieved was the Temkin isotherm in non-linear and linear form followed by Freundlich and Langmuir based on the error functions. Non-linear pseudo-first-order and pseudo-second-order kinetic models analyzed the adsorption data. The present work demonstrated that the non-linear method is a more suitable method to estimate the isotherm parameters than the linear method, and the pseudo-first-order model best fitted the corresponding experimental data.
The main challenges in wastewater treatment using adsorbents are the selection, development, and characterization of the absorbents. In this study, activated carbons (ACs) were prepared through ...chemical activation with phosphoric acid, followed by carbonization of banana root (BR). Proximate, ultimate, BET, FTIR, and FE-SEM analyses were employed to characterize the precursor and prepared ACs. A maximum BET surface area of 989
m
2
/
g
was observed for one of the ACs. The developed ACs were employed to remove methylene blue (MB) from synthetic wastewater at different initial concentrations (20–200 mg/L) and adsorption temperatures (25, 30, and 40
∘
C
) for 24 h in a batch mode. Adsorption isotherm models in linear and non-linear forms of Langmuir, Freundlich, and Temkin were considered to analyze experimental equilibrium data. For evaluation of the optimum isotherm, six different error analysis functions were used. Results indicated that the non-linear form of the Temkin isotherm model was the most suitable to explain the adsorption of MB. The maximum adsorption of 152.83
m
g
/
g
was observed for an adsorption temperature of 40
∘
C
and an initial concentration of 200 mg/L. The adsorption kinetic data were fitted with two models: pseudo-first-order and pseudo-second-order. The pseudo-second-order model was the best to explain the adsorption mechanism. The Weber and Morris intraparticle diffusion model was used to identify the rate-controlling step. The intraparticle diffusion was not only the rate-controlling step; another step like surface diffusion might also be involved in the adsorption process. Thermodynamic analyses were carried out, which revealed that the adsorption process was spontaneous and endothermic.
Graphical abstract
In the present study, identification of groundwater zones that are affected by anthropogenic contaminants based on litho-hydrogeological parameters has been attempted using multi-criteria decision ...analysis–analytical hierarchy process (MCDA–AHP) technique in an agriculturally intensive Arang block of Raipur district, Chhattisgarh, Central India. Litho-hydrogeological factors, such as geological and aquifer characteristics, land use–land cover, depth to water table, soil type, rainfall distribution, slope, geomorphological features, drainage density, elevation and lineament density parameters are considered for the delineation of anthropogenic contamination zones based on an integrated index model in Arc-GIS. Various input layers were assigned weights and then weight normalization process was adopted using Saaty’s AHP method to develop the integrated potential anthropogenic contamination zone (PACZ) map, based on the relative importance of anthropogenic contamination of groundwater. According to the proposed model majority of the study area falls under precarious zone, though certain areas fall under safe zone. In course of time, without proper planning the area could turn out to be moderately unsafe to unsafe zone. The PACZ map was validated with the fluoride concentration in groundwater as per National Rural Drinking Water Programme (NRDWP) report along with the measured nitrate concentration values. Model accuracy was achieved by agreement of about 82% of the fluoride values and 94% of the nitrate values with the proposed output map. Further validation of the model with fluoride and nitrate data was performed using computing similarity analysis with Pearson’s correlation coefficient which suggests anomalously higher concentrations of fluoride and nitrate ion concentration in certain areas of Arang block, which could be emanated from non-point anthropogenic sources. Additionally, Gibbs’s plot and saturation indices of fluorite and calcite suggest that groundwater chemistry is primarily controlled by aquifer lithological characteristics (rock–water interaction) and diffused anthropogenic contamination sources.
Improvisation of the biodiesel production using low-cost feedstock and the process optimisation is the perfect measure for the mitigation of high cost associated with the production process. In this ...current study, we are focussing on the extraction of rice bran oil (RBO) which is mainly considered underutilised waste material for the synthesis of biodiesel. Solvent extraction of RBO was performed with the aid of ultrasound and the study of various process parameters were exhibited using design of experiment by Taguchi model. The highest extraction efficiency was obtained at S/R ratio: 4:1 (ml/g), Agitation speed: 150 (rpm), Agitation time: 60 (min), Size range: 427.5 (micron), Sonication time (min): 15 (min) and Power level: 70 (KW). It was observed that the ultrasound-assisted extraction produced better quality oil than the extraction performed by conventional Soxhlet. Secondly, the esterification was performed using sulphuric acid as the acid catalyst and parametric optimization was performed for the enhancement of biodiesel yield using L9 orthogonal array. The key factors viz. agitation speed of 1000 rpm, methanol to oil ratio (M/O) of 10:1and reaction temperature of 60 °C; were found to be favourable for the attainment of the maximum yield of biodiesel.
A novel MgO/MgSO4 nanocatalyst was synthesized using solution combustion method with thiourea as the fuel. The in-situ inducement of sulfonated group over the basic catalyst, MgO, was carried out for ...the first time using thiourea for the production of biodiesel. The synthesized nanocatalyst with its bi-functional characteristics performed efficiently in the simultaneous transesterification and esterification of high free fatty acid (FFA) containing waste cooking oil (WCO) into biodiesel in the presence of ultrasound. The newly developed nanocatalyst was characterized by XRD, FESEM, EDS, FTIR and BET analyses. The resulting nanocatalyst possesses a specific surface area of 82 m2/g and a pore volume of 0.047 cm3/g. The high sulfur content of 13.65% of the novel catalyst developed facilitates its high acidic characteristics suitable for the esterification step. The optimization of the process carried out by the response surface methodology (RSM) predicted the optimized parameters as follows: methanol to oil molar ratio-9.4:1, catalyst loading-8.9 wt%, ultrasonic power-402 W and reaction time-46 min. The optimum yield of biodiesel predicted by the RSM was 98.8%. The synthesized nanocatalyst demonstrated high stability which established significant future perspective for industrial production of biodiesel from low cost, high FFA containing feedstock.
► Considerable surface area for mass transfer was created with ultrasound. ► Particle size distributions were modeled using linear combination of lognormal distributions. ► Ultrasonic energy ...dissipation ∼60
kJ/kg saturated benzoic acid in different solvents. ► Intrinsic mass transfer coefficient could be resolved from the volumetric mass transfer coefficient. ► Useful design correlation for Sherwood number in presence of ultrasound was proposed.
The efficacy of power ultrasound of 20
kHz in enhancing the volumetric mass transfer coefficient was investigated in this study. Breakage and dissolution of sparingly soluble benzoic acid dispersed in either water or 24% aqueous glycerol was monitored as a function of time and ultrasound power input. Particle size measurements were carried out at intermediate times during the experiment to estimate the mean particle size and surface area. Linear combination of lognormal distributions was found to fit the experimental particle size distribution data. The De Brouckere mean diameters (
d
43) obtained from the particle size distributions decreased with increase in the ultrasonic power level. Empirical correlations were developed for the evolution of surface area as a function of ultrasonic energy input per unit mass. The effect of ultrasound on the intrinsic mass transfer coefficient (
k
c) could be decoupled from the volumetric mass transfer coefficient (
k
c
a) as the surface area was also estimated. Different approaches involving either constant or variable intrinsic mass transfer coefficients were employed when carrying out the delineation. Mass transfer rates were enhanced due to both higher ultrasound induced intrinsic convective mass transfer coefficient and additional surface area created from particle breakage. To delineate the effects of particle breakage from solid dissolution, experiments were also carried out under non-mass transfer conditions by pre-saturating the solvents with benzoic acid. Both the solid–liquid systems examined in the present study attained saturation concentration when the ultrasonic energy input per unit mass was approximately 60
kJ/kg, irrespective of the ultrasonic power level setting.
Biodiesel is considered the prospective substitute for non-renewable fossil fuel-derived sources of energy. However, the high costs of feedstocks and catalysts inhibit its large-scale industrial ...implementation. From this perspective, the utilization of waste as the source for both catalyst synthesis and feedstock for biodiesel is a rare attempt. Waste rice husk was explored as a precursor to prepare rice husk char (RHC). Sulfonated RHC was employed as a bifunctional catalyst for the simultaneous esterification and transesterification of highly acidic waste cooking oil (WCO) to produce biodiesel. The sulfonation process coupled with ultrasonic irradiation proved to be an efficient technique to induce high acid density in the sulfonated catalyst. The prepared catalyst possessed a sulfonic density and total acid density of 4.18 and 7.58 mmol/g, respectively, and a surface area of 144 m
2
/g. A parametric optimization was conducted for the conversion of WCO into biodiesel using the response surface methodology. An optimal biodiesel yield of 96% was obtained under the conditions of methanol to oil ratio (13:1), reaction time (50 min), catalyst loading (3.5 wt%), and ultrasonic amplitude (56%). The prepared catalyst showed higher stability up to five cycles with biodiesel yield greater than 80%.
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