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This study evaluated the use of a renewable organic acid (citric acid) as homogeneous catalyst for the pretreatment of raw sugarcane bagasse (SB). A 22 central composite design with two factors (reaction time and citric acid concentration) was used to evaluate the effect of the factors on the chemical composition of the pretreated SB samples and enzymatic hydrolysis efficiency. The enzymatic hydrolysis experiments of the pretreated SB samples were performed using the enzymatic cocktail Cellic® CTec 3 and the total reducing sugars (TRS) released after enzymatic hydrolysis was determined. In addition, scanning electron microscopy and X-ray diffraction were used to examine the changes in the morphology and structure of the pretreated SB samples. The changes in the structure and chemical composition of the pretreated SB resulted in a high TRS concentration (28.2 g L−1) after enzymatic hydrolysis, for the pretreatment condition employing 6 wt% citric acid and 102.4 min, compared to the raw SB (3.06 g L−1). The pretreatment showed potential for application since a moderate conversion of polysaccharides in TRS was obtained, even though it was a pretreatment carried out under milder conditions. The pretreatment studied has the advantage of using weak and environmentally friendly acid catalyst, atmospheric pressure, and low temperature. • Pretreatment of sugarcane bagasse (SB) with citric acid was studied. • Chemical, structural and morphological changes of SB was investigated. • Changes in the SB was effective in improve sugar conversion by enzymatic hydrolysis. • High concentrations of total reducing sugars (28.2 g L−1) in comparison to the raw SB (3.06 g L−1) was obtained. [ABSTRACT FROM AUTHOR]

Organosolv delignification assisted by high–pressure carbon dioxide (HP–CO 2 ), a low cost, non–corrosive and recoverable compound was evaluated as a potential green pretreatment technology for lignin extraction from liquid hot water (LHW) pretreated sugarcane bagasse to produce fermentable sugars in a lignocellulosic biorefinery concept. In this study, LHW pretreated bagasse (180 °C for 20 min with a liquid–to–solid ratio ( LSR ) of 9 (v/w)) was delignified with an ethanol–water mixture (1:1, v/v) and HP–CO 2 as a co–solvent at milder temperatures (111.7–168.3 °C) and times (23.8–66.2 min) at a LSR of 5 (v/w). To evaluate the effects of varying operational conditions on the lignin content and delignification extent, while preserving the glucan fraction, a 2 2 central composite design was used as a factorial planning. Solid fractions with low lignin contents (7.35% and 10.78%) and high delignification extents (82.5% and 72.2%) with good glucan preservations (84.6% and 85.3%) were obtained at 140 °C for 45 min and 111.7 °C for 45 min, respectively. These solid fractions were subjected to enzymatic hydrolysis, yielding enzymatic conversions of 60.8% and 63.7%, respectively. [ABSTRACT FROM AUTHOR]

Highlights: [•] LHW-HP-CO2 evaluated as a potential green technology for hemicelluloses extraction. [•] At 100°C for 30min and 115°C for 60min xylan equivalent ranged 10–12g/L. [•] At 115°C for 60min, the cellulose preservation achieved 97.2%. [•] Enzymatic hydrolysis yielded 30.43g/L glucose and 41.17% cellulose conversion. [ABSTRACT FROM AUTHOR]

Abstract: Sugarcane bagasse cellulose was subjected to the extremely low acid (ELA) hydrolysis in 0.07% H2SO4 at 190, 210 and 225°C for various times. The cellulose residues from this process were characterized by TGA, XRD, GPC, FTIR and SEM. A kinetic study of thermal decomposition of the residues was also carried out, using the ASTM and Kissinger methods. The thermal studies revealed that residues of cellulose hydrolyzed at 190, 210 and 225°C for 80, 40 and 8min have initial decomposition temperature and activation energy for the main decomposition step similar to those of Avicel PH-101. XRD studies confirmed this finding by showing that these cellulose residues are similar to Avicel in crystallinity index and crystallite size in relation to the 110 and 200 planes. FTIR spectra revealed no significant changes in the cellulose chemical structure and analysis of SEM micrographs demonstrated that the particle size of the cellulose residues hydrolyzed at 190 and 210°C were similar to that of Avicel. [Copyright &y& Elsevier]

Abstract: This paper describes the organosolv delignification of depithed bagasse using glycerol–water mixtures without a catalyst. The experiments were performed using two separate experimental designs. In the first experiment, two temperatures (150 and 190°C), two time periods (60 and 240min) and two glycerol contents (20% and 80%, v/v) were used. In the second experiment, which was a central composite design, the glycerol content was maintained at 80%, and a range of temperatures (141.7–198.3°C) and time (23–277min) was used. The best result, obtained with a glycerol content of 80%, a reaction time of 150min and a temperature of 198.3°C, produced pulps with 54.4% pulp yield, 7.75% residual lignin, 81.4% delignification and 13.7% polyose content. The results showed that high contents of glycerol tend to produce pulps with higher delignification and higher polyoses content in relation to the pulps obtained from low glycerol content reactions. In addition, the proposed method shows potential as a pretreatment for cellulose saccharification. [Copyright &y& Elsevier]

Abstract: This study describes the preparation of two new chelating materials, MMSCB 3 and 5, derived from succinylated twice-mercerized sugarcane bagasse (MMSCB 1). MMSCB 3 and 5 were synthesized from MMSCB 1 using two different methods as described by . In the first method MMSCB 1 was activated with 1,3-diisopropylcarbodiimide and in the second with acetic anhydride (to form an internal anhydride) and later both were reacted with triethylenetetramine in order to obtain MMSCB 3 and 5. New obtained materials were characterized by mass percent gain, concentration of amine groups, FTIR, and elemental analysis. MMSCB 3 and 5 showed mass percent gain of 19.9 and 57.1%, concentration of amine groups of 2.0 and 2.1mmol/g, and nitrogen content of 5.8 and 4.4%. The capacity of MMSCB 3 and 5 to adsorb Cu2+, Cd2+, and Pb2+ from aqueous single metal ion solutions was evaluated at different contact times, pHs, and initial metal ion concentrations. Adsorption isotherms were well fitted by Langmuir model. Maximum adsorption capacities of MMSCB 3 and 5 for Cu2+, Cd2+, and Pb2+ were found to be 59.5 and 69.4, 86.2 and 106.4, 158.7 and 222.2mg/g, respectively. [Copyright &y& Elsevier]

In the second part of this series of studies, the bicomponent adsorption of safranin-T (ST) and auramine-O (AO) on trimellitated sugarcane bagasse (STA) was evaluated using equimolar dye aqueous solutions at two pH values. Bicomponent batch adsorption was investigated as a function of contact time, solution pH and initial concentration of dyes. Bicomponent kinetic data were fitted by the pseudo-first-order and pseudo-second-order models and the competitive model of Corsel. Bicomponent equilibrium data were fitted by the real adsorbed solution theory model. The antagonistic interactions between ST and AO in the adsorption systems studied contributed to obtain values of maximum adsorption capacity in mono- (Q max,mono) and bicomponent (Q max,multi) lower than unity (Q max,multi / Q max,mono at pH 4.5 for ST of 0.75 and AO of 0.37 and at pH 7 for ST of 0.94 and AO of 0.43). Mono- and bicomponent adsorption of dyes in a fixed-bed column was evaluated at pH 4.5. The breakthrough curves were fitted by the Thomas and Bohart-Adams original models. Desorption of ST in a fixed-bed column was studied. The results obtained from the bicomponent batch and continuous adsorption showed that the presence of ST most affected the AO adsorption than the presence of AO affected the ST adsorption. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Sugarcane bagasse cellulose mixed ester succinate phthalate (SBSPh) was synthesized by a novel one-pot reaction method. The effects of temperature, time and mole fraction of succinic anhydride (χ SA) on the responses weight gain (wg), number of carboxylic acid groups (n T,COOH), and adsorption capacity (q) of Co2+ and Ni2+ were evaluated by a 23 experimental design. The chemical structure of the material was elucidated by Fourier transform infrared, 13C Multiple Cross-Polarization solid-state NMR spectroscopy and 1H NMR relaxometry. The best SBSPh synthesis condition (100 °C, 11 h, χ SA of 0.2) yielded a wg of 59.1%, n T,COOH of 3.41 mmol g−1, and values of q Co 2+ and q Ni 2+ of 0.348 and 0.346 mmol g−1, respectively. The Sips model fitted better the equilibrium data, and the maximum adsorption capacities (pH 5.75 and 25 °C) estimated by this model were 0.62 and 0.53 mmol g−1 for Co2+ and Ni2+, respectively. The Δ ads H ° values estimated by isothermal titration calorimetry were 8.43 and 7.79 kJ mol−1 for Co2+ and Ni2+, respectively. Desorption and re-adsorption efficiencies were evaluated by a 22 experimental design, which showed that SBSPh adsorbent can be recovered and reused without significant loss of adsorption capacity. [ABSTRACT FROM AUTHOR]

Trimellitated-sugarcane bagasse (STA) was used as an environmentally friendly adsorbent for removal of the basic dyes auramine-O (AO) and safranin-T (ST) from aqueous solutions at pH 4.5 and 7.0. Dye adsorption was evaluated as a function of STA dosage, agitation speed, solution pH, contact time, and initial dye concentration. Pseudo-first- and pseudo-second-order, Elovich, intraparticle diffusion, and Boyd models were used to model adsorption kinetics. Langmuir, Dubinin-Radushkevich, Redlich-Peterson, Sips, Hill-de Boer, and Fowler-Guggenheim models were used to model adsorption isotherms, while a Scatchard plot was used to evaluate the existence of different adsorption sites. Maximum adsorption capacities for removal of AO and ST were 1.005 and 0.638 mmol g −1 at pH 4.5, and 1.734 and 1.230 mmol g −1 at pH 7.0, respectively. Adsorption enthalpy changes obtained by isothermal titration calorimetry (ITC) ranged from −21.07 ± 0.25 to −7.19 ± 0.05 kJ mol −1 , indicating that both dyes interacted with STA by physisorption. Dye desorption efficiencies ranged from 41 to 51%, and re-adsorption efficiencies ranged from 66 to 87%, showing that STA can be reused in new adsorption cycles. ITC data combined with isotherm studies allowed clarification of adsorption interactions. [ABSTRACT FROM AUTHOR]

The present study investigated the potential of UASB inoculum, by itself or mixed to nitrogenous residue (fresh bovine manure – FBM) or to adapted microorganisms (bovine rumen – BR), for biomethanation of raw and pretreated sugarcane bagasse (SB) by solid-state anaerobic digestion. The influence of autohydrolysis and organosolv pretreatment conditions on the efficiency of biomethanation process was also evaluated by means of kinetic parameters. Akaike Information Criterion was used to statistically evaluate methane production, and the multi-stage model exhibited the highest fit among the models tested. FBM addition resulted in improvements in the C/N ratio, higher yield (143.3NL CH4 kg VS −1 ) and higher rate constant (3.05NL CH4 kg VS −1 day −1 ) for CH 4 production from raw SB without any lag phase when compared to UASB inoculum itself which exhibited 5.6 days of lag phase. The FBM also led to a better inoculum adaptation to substrates which contained inhibitors such as xylooligomers and lignin fragments, and had lower C5 sugar content. [ABSTRACT FROM AUTHOR]

In the present study, the ozonation of sugarcane bagasse (SB) at different operational conditions (pH, time, liquid-to-solid ratio ( LSR )) was evaluated with the aim of generating a soluble liquid fraction (SLF) suitable for biogas production (CH 4 and H 2 ) via anaerobic digestion and a solid fraction prone to enzymatic hydrolysis and 2G ethanol production. The SLFs obtained were characterized for sugars, total organic carbon (TOC), soluble lignin, furans and other components identified by GC/MS. The results showed that it was possible to solubilize 45.2% of lignin, 48.3% of hemicelluloses and 40.7% of cellulose with the use of ozone (8 mg min −1 ) at pH 11 for 15 min, employing a LSR of 13.3 mL g −1 . The best results of biochemical methane potential (BMP) and biochemical hydrogen potential (BHP) were 2.6 Nm 3 of CH 4 and 0.18 Nm 3 of H 2 per kg of TOC, respectively. An energy balance for the best pretreatment conditions indicates that the combustion of such biogas led to an energy surplus of 0.1 MJ kg −1 SB for methane and to an energy deficit of 0.191 MJ kg −1 SB for hydrogen. Potentially inhibitory compounds for anaerobic digestion such as oxalic acid, butanal, xylitol, furanone, benzaldehyde, d -erythrotetrofuranose, d -erythro-pentofuranose and 2,5-furandione were identified in the hydrolysates, which negatively affected the anaerobic digestion and the energy balance. Nevertheless, the energy generated from the hydrolysates (as biogas) and from the ozonized solid fraction (as 2G ethanol) offsets the ozonation energy input and led to positive energy balance. [ABSTRACT FROM AUTHOR]

This study evaluated the synergistic efficiency of crude enzymatic extracts (CEE) produced by fungal strains Aspergillus fumigatus SCBM6 (AFE) and Aspergillus niger SCBM1 (ANE) in the hydrolysis of alkali pretreated sugarcane bagasse (2% NaOH (w v −1 ), ∼100 °C, 4 h and liquid-to-solid ratio of 25 (v w −1 )). CEEs were produced by solid-state fermentation (SSF) and presented high concentration of β-glucosidase (AFE = 78.4 U g −1 and ANE = 43.02 U g −1 ), β-xylosidase (ANE = 78.0 U g −1 ) and xylanase (AFE = 1774.5 U g −1 and ANE = 3289.6 U g −1 ). A 2 4 full design of experiments was used to optimize the hydrolysis of pretreated bagasse as a function of time, temperature, amount of pretreated bagasse and AFE-to-ANE ratio. After hydrolysis optimization, the maximum concentration of total reducing sugars (TRS) was 21.68 g L −1 . It was also noticed a significant production of xylose (135.59 mg) and arabinose (58.10 mg) per gram of hemicelluloses and a slight production of glucose (20.18 mg) per gram of cellulose. As fungi consortium were excellent producers of hemicellulases, it is suggested that they could be used for pentoses saccharification and production of ethanol via C-5 fermentation, xylitol, biopolymers, among other bioproducts. [ABSTRACT FROM AUTHOR]

Bioethanol production from lignocellulose biomass offers a solution to current environmental challenges caused by fossil fuel energy resources, while satisfying the biorefinery concept. In this study, two-stage fractionation (autohydrolysis (AH) followed by glycerol organosolv delignification (GOD)) of sugarcane bagasse (SCB) was studied as a function of temperature, time, glycerol content and liquid-to-solid ( LSR ) ratio using experimental designs. The effect of three different AH pretreatment severities on delignification extents ( DE ) of the solid fractions were also evaluated. Scanning electron microscopy was used to examine the changes in the surface of SCB pretreated by AH. Energy balances of four fractionation conditions were estimated, and the use of pure and crude glycerol in GOD was evaluated based on DE and lignin contents. A DE of ∼64% was obtained at 210.3 °C, 40 min, LSR of 6.5 (v/w) and 80% (v/v) pure glycerol for GOD of SCB pretreated by AH at 175.8 °C, 49 min and LSR of 5.3 (v/w), which resulted in an energetic profitability ( EP ) of 141.48 MJ/kg SCB . The use of crude glycerol at 80% (v/v) under the same process conditions optimized for pure glycerol also proved to be feasible ( DE of ∼64% and EP of 142.67 MJ/kg SCB ), widening the possibilities for its direct use in GOD of SCB pretreated by AH in a 2G bioethanol integrated plant. [ABSTRACT FROM AUTHOR]

This study aimed at optimizing the net energy recovery from hydrogen and methane production through anaerobic digestion of the hemicellulose hydrolysate (HH) obtained by desirable conditions (DC) of autohydrolysis pretreatment (AH) of sugarcane bagasse (SB). Anaerobic digestion was carried out in a two-stage (acidogenic-methanogenic) batch system where the acidogenic phase worked as a hydrolysis and biodetoxification step. This allowed the utilization of more severe AH pretreatment conditions, i.e. T = 178.6 °C and t = 55 min (DC3) and T = 182.9 °C and t = 40.71 min (DC4). Such severe conditions resulted in higher extraction of hemicelluloses from SB (DC1 = 68.07%, DC2 = 48.99%, DC3 = 77.40% and DC4 = 73.90%), which consequently improved the net energy balance of the proposed process. The estimated energy from the combustion of both biogases (H 2 and CH 4 ) accumulated during the two-stage anaerobic digestion of HH generated by DC4 condition was capable of producing a net energy of 3.15 MJ·kg SB −1 dry weight . [ABSTRACT FROM AUTHOR]

This study aimed to optimize through design of experiments, the process variables (temperature – T , time – t and solid-to-liquid ratio – SLR ) for sugarcane bagasse (SB) autohydrolysis (AH) to obtain hemicellulose hydrolyzates (HH) prone to anaerobic digestion (AD) and biochemical methane production (BMP). The results indicated that severe AH conditions, which lead to maximum hemicelluloses dissolution and sugar content in the HH, were not the best for BMP, probably due to the accumulation of toxic/recalcitrant compounds (furans and lignin). Mild AH conditions (170 °C, 35 min and SLR = 0.33) led to the highest BMP (0.79 Nm 3 kg TOC −1 ), which was confirmed by the desirability tool. HH produced by AH carried out at the desired condition DC2 (178.6 °C, 43.6 min and SLR = 0.24) showed the lowest accumulation of inhibitory compounds and volatile fatty acids (VFA) and highest BMP (1.56 Nm 3 kg TOC −1 ). The modified Gompertz model best fit the experimental data and led to a maximum methane production rate ( R ) of 2.6 mmol CH 4 d −1 in the best condition. [ABSTRACT FROM AUTHOR]

This study describes, in detail, the chemical modification of sugarcane bagasse with phthalic anhydride to produce a carboxylate-functionalized sugarcane bagasse (SPA). The optimized modification conditions yielded SPA with a percent weight gain of 77.08% and an amount of carboxylic acid groups of 4.76 mmol/g. The SPA was characterized by PZC, FTIR, elemental analysis, TGA, and SEM-EDX. An SPA adsorbent was used to remove Co 2+ , Cu 2+ , and Ni 2+ from aqueous solution in mono- and multicomponent systems in batch mode. The adsorption kinetics followed a pseudo-second-order model. The adsorption rate constants assumed the following order: k 2,Co 2+ > k 2,Ni 2+ > k 2,Cu 2+ . Four mono- and multicomponent isotherm models were used to model the adsorption data. Monocomponent data were well described by the Langmuir model, whereas bicomponent data were well described by the modified extended Langmuir and P -Factor models. The maximum adsorption capacities ( Q max,mono ) for the Langmuir model were 0.561, 0.935, and 0.932 mmol/g for Co 2+ , Cu 2+ , and Ni 2+ , respectively. Adsorption in bicomponent systems revealed that Cu 2+ suppressed the adsorption of Co 2+ and Ni 2+ , whereas Ni 2+ suppressed the adsorption of Co 2+ . Desorption studies revealed that the SPA adsorbent could be fully desorbed with a 1 mol/L HNO 3 solution. [ABSTRACT FROM AUTHOR]

A new carboxylated-functionalized sugarcane bagasse (STA) was prepared through the esterification of sugarcane bagasse with trimellitic anhydride. The optimized synthesis conditions yield STA with a percent weight gain of 73.9% and the number of carboxylic acid groups accounted for 3.78 mmol/g. STA was characterized by FTIR, elemental analysis, TGA, PZC, and SEM. Adsorption kinetics followed a pseudo-second-order model. The adsorption rate constant showed the following order: k 2,Ni 2+ > k 2,Cu 2+ > k 2,Co 2+ . Four mono- and multi-component isotherm models were used to model the adsorption systems. Monocomponent experimental data were fitted to Langmuir and Sips models; whereas, multicomponent data were fitted to modified extended Langmuir and P -factor models. The maximum adsorption capacities ( Q max,mono ) obtained from the Langmuir model were 1.140, 1.197, and 1.563 mmol/g for Co 2+ , Cu 2+ , and Ni 2+ , respectively. The competitive studies demonstrated that the multicomponent adsorption capacity ( Q max,multi ) was smaller than Q max,mono , as a result of the interaction between the metal ions. Desorption studies showed that all metal ions could be fully desorbed from STA. [ABSTRACT FROM AUTHOR]

A new carboxylate-functionalized sugarcane bagasse (SMA) was prepared via a solvent-free procedure involving esterification of sugarcane bagasse with Meldrum's acid. The optimized conditions provided SMA with a percent weight gain of 86.0% and 4.69 ± 0.20 mmol/g of carboxylic acid groups. SMA was characterized by FTIR, TGA, elemental analysis and SEM. Kinetic experiments showed that the amount of crystal violet adsorbed increased with increasing temperature and equilibrium was reached at 12 h. Adsorption kinetics followed a pseudo-second-order model. The Arrhenius and Eyring models were used to obtain the activation energy and changes in free energy, enthalpy, and entropy of activation for the adsorption process. The calculated activation energy (14.14 kJ/mol) suggested physical adsorption of CV onto SMA. The equilibrium data were well fitted to the Langmuir and Sips isotherms. Maximum adsorption capacity was 692.1 mg/g at 45 °C. Thermodynamic parameters such as changes in free energy, enthalpy and entropy were also determined. [ABSTRACT FROM AUTHOR]