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This study reports the use of multivariate tools to optimize the synthesis of a new agricultural-based biosorbent derived from sugarcane bagasse (SB) for the removal of Cd(II) and Pb(II) from aqueous solutions, as well as to optimize the process of desorption of these ions from the spent biosorbent using an acidic solution. The effects of the reaction parameters temperature (T), time (t), and the ratio of 1,2,3,4-butanetetracarboxylic acid dianhydride (BTCAD) to raw SB (wBTCAD wraw SB−1) on the chemical modification of raw SB with BTCAD and on the equilibrium adsorption capacity (qe) for Cd(II) and Pb(II) were investigated by application of a 23 Doehlert experimental design (DED), followed by optimization using a statistical desirability tool to produce the best adsorbent in terms of performance and cost. The best reaction condition was wBTCAD wraw SB−1 of 4.0 g g−1, t of 1 h, and T of 70 ºC. The optimal synthesis condition resulted in a modified sugarcane bagasse (MSB) that provided qe values for Cd(II) and Pb(II) of 0.50 and 0.61 mmol g−1, respectively, obtained under the following conditions: 0.311 mmol Cd(II) L−1, 0.632 mmol Pb(II) L−1, pH 5.0, 4 h, 0.2 g L−1 MSB, 130 rpm, and 25 °C. The desorption of Cd(II) and Pb(II) from MSB was investigated by a 22 DED, with optimization using the desirability tool to obtain the best desorption condition in terms of HNO3 solution concentration ( C HNO 3 ) and t. The desorption efficiencies for Cd(II) and Pb(II) were 90 ± 4% and 88 ± 3%, respectively, obtained using 0.7 mol L−1 HNO3, t of 42 min, and 1.0 g L−1 MSB-M(II) (M = Pb or Cd). Infrared spectroscopy was used to investigate the natures of the interactions involved in the adsorption of Cd(II) and Pb(II) on MSB, as well as possible changes in the chemical structure of MSB after desorption. The synthesis of MSB can be performed under mild reaction conditions (t = 1 h, T = 70 ºC), and the solvents used can be recovered by distillation. BTCA is commercially available at moderate cost and can alternatively be obtained employing microbial succinic acid, metal-free catalysis, and modest use of petrochemical feedstocks. Furthermore, MSB can be reused, which could contribute to increasing the economic feasibility of water and wastewater treatment processes. [ABSTRACT FROM AUTHOR]

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: In this study the adsorption of cationic dyes by modified sugarcane bagasse with EDTA dianhydride (EB) was examined using methylene blue (MB) and gentian violet (GV) as model compounds in aqueous single solutions. The synthesized adsorbent (EB) was characterized by FTIR, elemental analysis, and BET. The capacity of EB to adsorb dyes was evaluated at different contact times, pH values, and initial dye concentrations. According to the obtained results, the adsorption processes could be described by a pseudo-second-order kinetic model. The adsorption isotherms were well fitted by the Langmuir model. Maximum adsorption capacities for MB and GV on EB were found to be 202.43 and 327.83 mg/g, respectively. The free energy change during adsorption of MB and GV was found to be −22.50 and −24.21 kJ/mol, respectively, suggesting that chemisorption is the main mechanism controlling the adsorption process. [Copyright &y& Elsevier]

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: In a previous work, chemically modified cellulose (EMC) and sugarcane bagasse (EMMB) were prepared from mercerized cellulose (MC) and twice-mercerized sugarcane bagasse (MMB) using ethylenediaminetetraacetic dianhydride (EDTAD) as modifying agent. In this work we described in detail the modification of these materials in function of reaction time and EDTAD amount in the reaction media. The resistance of ester bond at pH 1, 2, 11, and 12 was also evaluated by FTIR. The results were used to model the hydrolysis process and a kinetic model was proposed. The modified materials (EMMB and EMC) were used to adsorb Ca2+ and Mg2+ ions from aqueous single solutions. The adsorption isotherms were developed at two pH values. These materials showed maximum adsorption capacities for Ca2+ and Mg2+ ions ranging from 15.6 to 54.1mg/g and 13.5 to 42.6mg/g, respectively. The modified material from sugarcane bagasse (EMMB) showed larger maximum adsorption capacities than modified material from cellulose (EMC) for both metals. [Copyright &y& Elsevier]

In the context of a sugarcane biorefinery, sugarcane bagasse produced may be pretreated generating a solid and liquid fraction. The solid fraction may be used for 2G bioethanol production, while the liquid fraction may be used to produce biogas through anaerobic digestion. The aim of this study consisted in evaluating the anaerobic digestion performance of hemicellulose hydrolysate produced after hydrothermal pretreatment of sugarcane bagasse. For this, hydrothermal pretreatment was assessed in a continuous upflow anaerobic sludge blanket (UASB) reactor operated at a hydraulic retention time (HRT) of 18.4 h. Process performance was investigated by varying the dilution of sugarcane bagasse hydrolysate with a solution containing xylose and the inlet organic loading rate (OLR). Experimental data showed that an increase in the proportion of hydrolysate in the feed resulted in better process performance for steps using 50% and 100% of real substrate. The best performance condition was achieved when increasing the organic loading rate (OLR) from 1.2 to 2.4 g COD/L·d, with an organic matter removal of 85.7%. During this period, the methane yield estimated by the COD removal would be 270 L CH 4 /kg COD. Nonetheless, when further increasing the OLR to 4.8 g COD/L·d, the COD removal decreased to 74%, together with an increase in effluent concentrations of VFA (0.80 g COD/L) and furans (115.3 mg/L), which might have inhibited the process performance. On the whole, the results showed that anaerobic digestion of sugarcane bagasse hydrolysate was feasible and may improve the net energy generation in a bioethanol plant, while enabling utilization of the surplus sugarcane bagasse in a sustainable manner. [ABSTRACT FROM AUTHOR]

This study evaluated the pretreatment of sugarcane bagasse (SCB) with dilute citric acid solution for biogas production. The black liquor (BL) from pretreatment and residual solid fraction (RSF) obtained after enzymatic hydrolysis were used as substrates for the biogas production. After saccharifications of the pretreated solid fractions performed with Cellic® CTec 3 cocktail, the highest concentration of total reducing sugars (TRS) was in the range of 10.7–184.8 g L−1 and the sugar yields were in the range of 3.5–88.8%. For BL, the contents of glucose, xylose, and arabinose were in the range of 1.9–8.9 g L−1, 4.0–24.7 g L−1, and 0.2–5.4 g L−1, respectively. Biogas production from BL and RSF resulted, respectively, in maximum values of 563.6 and 57.8 NmL g COD −1, indicating the feasibility of using dilute citric acid pretreatment coupled to biogas production in biorefineries. Brief energy and economic assessment were carried out considering the energy balance (thermal energy generated by burning biogas - thermal energy spent in the pretreatment), as well as revenue from a possible sale of electricity generated in a combined heat and power system. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: [•] Novel application for adsorbents after treating solutions containing metal ions. [•] New biobased heterogeneous catalysts were prepared for monoterpenes oxidation. [•] Production of high economic value oxygenated derivatives from monoterpenes. [•] Conversions among 49 and 78% and combined selectivity up to 59% were obtained. [Copyright &y& Elsevier]

In the second part of this series of studies, the monocomponent adsorption of Cu 2+ , Co 2+ and Ni 2+ onto STA adsorbent in a fixed-bed column was investigated and optimized using a 2 2 central composite design. The process variables studied were: initial metal ion concentration and spatial time, and the optimized responses were: adsorption capacity of the bed ( Q max ), efficiency of the adsorption process ( EAP ), and effective use of the bed ( H ). The higher Q max for Cu 2+ , Co 2+ and Ni 2+ were 1.060, 0.800 and 1.029 mmol/g, respectively. The breakthrough curves were modeled by the original Thomas and Bohart-Adams models. The changes in enthalpy (Δ ads H °) of adsorption of the metal ions onto STA were determined by isothermal titration calorimetry (ITC). The values of Δ ads H ° were in the range of 3.0–6.8 kJ/mol, suggesting that the adsorption process involved physisorption. Desorption ( E des ) and re-adsorption ( E re-ads ) of metal ions from the STA adsorbent were also investigated in batch mode, and the optimum conditions were applied for three cycles of adsorption/desorption in a fixed bed column. For these cycles, the lowest values of E des and E re-ads were 95 and 92.3%, respectively, showing that STA is a promising candidate for real applications on a large scale. [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]

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]

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]

• The proposed SB fractionation strategy led to substantial savings of H 2 O 2. • Alkaline extraction after hydrothermal pretreatment led to high delignification. • The higher accessibility of pretreated SB led to an enzymatic conversion of 88.9%. • 190.8 L ethanol ton SB −1 were produced by fermentation using S. cerevisiae LBCM1047. • The anaerobic digestion of residual liquid streams produced 27.46 Nm3 CH4 ton SB −1. The fractionation of sugarcane bagasse (SB) by hydrothermal pretreatment (HP, autohydrolysis) followed by alkaline extraction (AE) and advanced oxidative pretreatment (AOP) for production of second-generation ethanol and biogas was investigated. The AOP of SB was optimized using a Doehlert design, varying the applied H 2 O 2 load, liquid-to-solid ratio (LSR), and time. The responses evaluated were yield (Y), residual cellulose (RC), delignification (DE), and enzymatic conversion (EC). The AE of SB pretreated by HP led to 61.8% DE (using 0.2 mol L−1 NaOH). This high lignin removal enabled substantial savings of H 2 O 2 in the AOP. The optimized AOP conditions led to 78% Y , 82.2% RC , 42.7% DE , and 88.9% EC (overall glucose yield of 60.9%). Fermentation of the enzymatic hydrolysate with Saccharomyces cerevisiae yielded 190.8 L ethanol ton SB −1. Biogas production by anaerobic digestion of residual liquid streams of the pretreatment steps yielded 27.46 NL CH4 kg SB −1. An energy balance was estimated for the SB fractionation. [ABSTRACT FROM AUTHOR]

• The anaerobic co-digestion (AcD) of sugarcane biorefinery wastes was investigated. • Hemicelluloses hydrolysate, yeast extract (YE), vinasse and SBFA were used in AcD. • Sugarcane bagasse fly ash (SBFA) act as an adsorbent for toxic compounds during AcD. • The nutritional supplements and alkalinity for AcD were provided by YE and SBFA. • A positive energy balance was obtained by the net energy generated by AcD system. In this study the anaerobic co-digestion (AcD) of sugarcane biorefinery by-products, i.e. hemicelluloses hydrolysate (HH) (obtained by hydrothermal pretreatment of sugarcane bagasse), vinasse, yeast extract (YE) and sugarcane bagasse fly ashes (SBFA), was optimized by means of biochemical methane potential experiments. The best experimental conditions of AcD (25–75% HH-to-vinasse mixture ratio; 1.0 g L−1 YE; 15 g L−1 SBFA and 100–0% HH-to-Vinasse; 1.5 g L−1 YE; 45 g L−1 SBFA) led to the production of 0.279 and 0.267 Nm3 of CH 4 per kg of chemical oxygen demand (COD) with an energy surplus of 0.43 and 0.34 MJ kg SB−1, respectively. Adsorption experiments using SBFA were carried out and showed this residue could adsorb up to 61.71 and 17.32 mg g−1 of 5-hydroxymethyl-2-furfuraldehyde and 2-furfuraldehyde, thereby reducing toxicity and improving biogas production. [ABSTRACT FROM AUTHOR]