Ozonolysis Pretreatment Research Articles

Process configuration of combined ozonolysis and anaerobic digestion for wastewater treatment

Abstract Industrial activities and increased human population have made wastewater streams not entirely amenable to conventional treatment methods. Anaerobic digestion (AD) can treat such wastewaters with the advantage of bioresource recovery. However, the presence of solids and recalcitrant compounds in most wastewater streams may affect the AD process. Thus, combining AD with advanced oxidation processes (AOPs) such as ozonolysis is necessary. Ozonolysis can improve the biodegradability of wastewater substrates or eliminate biorecalcitrant pollutants that escape the AD process. This study combined ozonolysis with AD to treat waste activated sludge (WAS) and distillery wastewater (DWW). When applied as a pre-treatment, ozonolysis caused the rigid cell walls in WAS to rupture and solubilised the extracellular polymeric substances (EPS), leading to increased biodegradability. For the DWW, ozonolysis pre-treatment reduced the biorecalcitrant aromatic compounds to simple aliphatic compounds, thereby increasing biodegradability. In the ensuing anaerobic process, the WAS pre-treatment improved TSS and COD reductions and a 230% increase in cumulative biogas production. For the DWW, the ozonolysis pre-treatment did not significantly impact COD reduction or biogas production; however, ozonolysis as a post-treatment removed the color causing biorecalcitrant melanoidins from the anaerobically digested effluent and solubilised the sludge (TSS) washed out from the AD unit. Therefore, the AD-ozonolysis process configuration depends on the substrate being treated. Ozonolysis is best applied pre-AD for WAS treatment and post-AD for DWW.

Kinetic and dynamic analysis of ozonolysis pre-treatment of empty fruit bunch in a well-mixed reactor for sugar production

Pre-treatment is the key step in biorefinery for enhancing cellulose accessibility from lignocellulosic biomass (LB) such as empty fruit bunch (EFB), which contains highly valuable cellulose. Ozonolysis pre-treatment appears as a promising green alternative for isolation of EFB to cellulose. This study develops the diffusion–reaction model of EFB ozonolysis inside a well-mixed novel OzBiONY® ozonolysis reactor at lab scale production. The mathematical model is numerically solved using COMSOL Multiphysics® software. Kinetic reaction parameters are computationally estimated via gradient-based Sparse Nonlinear Optimizer (SNOPT) method with sequential quadratic programming (SQP) algorithm. The evolution of ozone velocity and concentration profiles inside the reactor are simulated by computational fluid dynamics (CFD) method to study the effect of biomass particle sizes. The larger particle size consumes higher ozone (k1 = 2.23 m3/mol∙s) compared to the smaller particle size (k1= 0.09 m3/mol∙s). This reveals that larger biomass particle confers faster delignification rate and a much higher degradation of insoluble lignin. The simulation results demonstrate ozone velocity at the surface of larger particle is lower, but the surface concentration of ozone is higher. The diffusion–reaction model of EFB ozonolysis elucidates the plausible reaction pathway of lignin degradation via ozonolysis pre-treatment with minimum objective function (Z) of 1.41 × 10−3. From experimental results, the highest lignin degradation is 78 wt.% and the highest glucose yield is 12 wt.%. The outcomes of this research will contribute to the development of smart biorefinery technology and systems for sugar production in a sustainable and circular economy.

Modelling of ozone multiphase flow behaviour in an ozonolysis pretreatment reactor

Ozonolysis pretreatment of lignocellulosic biomass (LB) is envisaged as a green and effective method to selectively remove lignin for subsequent bio-based processing. Herein, this study investigates the ozone multiphase flow behaviour of an ozonolysis pretreatment reactor for lignin degradation of oil palm empty fruit bunch (EFB). A coupled transport-reaction model is simulated using Computational Fluid Dynamic (CFD) via COMSOL Multiphysics® software to visualize the ozone multiphase flow behaviour in non-porous and porous bed regions. Numerical findings indicate the pressure drop across porous bed linearly increases with superficial ozone velocity. Simulation results also reveal that the relative pressure across the biomass bed reduces by reducing the biomass bed length. The present work provides preliminary insights for ozonolysis reactor design and optimum operations of biomass pretreatment for up-scaling and commercialization purposes.

Fractionation of Oil Palm Fronds (OPF) by Ozonolysis for Enhanced Sugar Production

This study investigates the potential of ozonolysis pretreatment on oil palm frond (OPF) for enhancing total reducing sugar (TRS) recovery. The OPF is pretreated by ozonolysis prior to two-step acid hydrolysis. The effect of ozonolysis pretreatment on the physico-chemical properties of OPF is scrutinized followed by the effect of process parameters on lignin degradation and TRS recovery. The presence of lignin-rich and cellulose-rich fractionates are proven by TGA. The XRD reveals crystallinity after pretreatment is increases while crystal size reduces indicating the removal of amorphous lignin region. The structure of OPF is disrupted during the pretreatment revealing the cellulose rosette structure in treated OPF as shown by FeSEM. Ultimately, TRS recovery increases up to 62.3 % with 90 % lignin degradation. This testifies ozonolysis is pertinent for enhancing sugar yields in acid hydrolysis. Among the process parameters, OPF particle size is the most significant followed by reaction time, moisture content, and ozone flowrate. The findings of this work contribute to new information about the pretreatment of biomass by ozonolysis.

Soaking and ozonolysis pretreatment of sugarcane straw for the production of fermentable sugars

In the present study, sugarcane straw residue (SCS) is used to generate fermentable sugars. Impregnation in different media and ozonolysis were combined for SCS treatment. The best results were obtained for the basic medium (80 °C at atmospheric pressure for 8 h) followed by ozonolysis (rotary reactor, ozone concentration of 0.24% (w/w), 60 min of reaction and 35% moisture content). Increasing the ozone concentration from 0.24% to 1.3% (w/w) did not increase the amount of glucose released (yields of 60.8 and 60.2%, respectively) indicating that no high ozone concentrations are required. The chemical characterization of the treated material showed that there were no losses due to holocellulose dissolution. In contrast, the cellulose and hemicellulose content increased by 75% and 42%, respectively when compared to the raw material, while the lignin content decreased by 47%. Samples subjected to ozonolysis showed the greatest reduction in the recalcitrance to enzymatic hydrolysis, reaching 60 and 71% of yield in glucose and xylose conversion, respectively, when compared to the impregned material (26 and 31% respectively) and the raw material (4 and 5%).

Optimization of Particle Size, Moisture Content and Reaction Time of Oil Palm Empty Fruit Bunch Through Ozonolysis Pretreatment

Optimization of Particle Size, Moisture Content and Reaction Time of Oil Palm Empty Fruit Bunch Through Ozonolysis Pretreatment

Ozonolysis pre-treatment of waste activated sludge for solubilization and biodegradability enhancement

Handling of waste activated sludge (WAS) has been a great problem due to its low biodegradability which is contributed by the biorecalcitrant bacterial cells from the activated sludge process. Moreover, the sludge is poorly soluble which makes it difficult to subject to a further biological treatment downstream. This study investigated the application of ozonolysis pre-treatment for the solubilization and biodegradability enhancement of municipal WAS. Ozonolysis led to sludge solubilization as was shown by a 50% reduction in total suspended solids (TSS). Subsequently, the dissolved organic carbon (DOC) increased by 25%, and sludge biodegradability increased two-folds. The mechanism of sludge solubilization was explained through cell content analysis which revealed biomass cell wall rapture during ozonolysis leading to the release of the cellular contents including humic substances, proteins, phosphates, nitrates and carbohydrates into the supernatant. The soluble proteins decreased by 98% while carbohydrates increased four-fold. Additionally, sulphates in the supernatant increased from 18 mg/L to 45 mg/L while nitrates increased from 0 mg/L to 85 mg/L indicating oxidation of the organic nitrogen and phosphorus which are constituents of the biomass cell protein; this can provide nutrient balance in the downstream biological treatment method. Thermogravimetric (TGA) analysis showed that the weight loss for ozone-treated WAS was 10% while that for the raw WAS was 20% further indicating that ozonolysis had solubilized the volatile and organic components of the treated WAS. Ozonolysis is a promising technology for the pre-treatment of WAS before anaerobic digestion for stabilization and energy recovery.

Effect of ozonolysis pretreatment parameters on the sugar release, ozone consumption and ethanol production from sugarcane bagasse

A L9(3)4 orthogonal array (OA) experimental design was applied to study the four parameters considered most important in the ozonolysis pretreatment (moisture content, ozone concentration, ozone/oxygen flow and particle size) on ethanol production from sugarcane bagasse (SCB). Statistical analysis highlighted ozone concentration as the highest influence parameter on reaction time and sugars release after enzymatic hydrolysis. The increase on reaction time when decreasing the ozone/oxygen flow resulted in small differences of ozone consumptions. Design optimization for sugars release provided a parameters combination close to the best experimental run, where 77.55% and 56.95% of glucose and xylose yields were obtained, respectively. When optimizing the grams of sugar released by gram of ozone, the highest influence parameter was moisture content, with a maximum yield of 2.98gSUGARS/gO3. In experiments on hydrolysates fermentation, Saccharomyces cerevisiae provided ethanol yields around 80%, while Pichia stipitis was completely inhibited.

Multi response optimization of oil palm frond pretreatment by ozonolysis

Oil palm frond (OPF) is a promising feedstock for the second-generation biofuel. However, the recalcitrant lignin layer conceals the cellulose component in the OPF and thus, curtails the conversion of cellulose to the value-added chemicals. The ozonolysis pretreatment is envisaged as an effective method for lignin degradation. This study investigated the influence of OPF particle size, moisture content, reaction time, ozone flowrate as well as their interaction, on lignin degradation and total reducing sugar (TRS) recovery by response surface methodology (RSM). The experiments conducted were based on Box-Behnken design (BBD). The process condition for the optimum lignin degradation and TRS recovery was determined by desirability function. The RSM analysis revealed that the interaction of particle size–moisture content was important for the lignin degradation while the interaction of moisture content–reaction time during ozonolysis was crucial for TRS recovery. Both the lignin degradation and TRS recovery at 84.7wt.% and 99.9%, respectively were optimized simultaneously under the recommended optimum conditions. The pre-treated OPF under the optimum conditions yield the levulinic acid equivalent to the commercial cellulose.

Ozonolysis pretreatment of maize stover: The interactive effect of sample particle size and moisture on ozonolysis process

Maize stover was ozonolyzed to improve the enzymatic digestibility. The interactive effect of sample particle size and moisture content on ozonolysis was studied. After ozonolysis, both lignin and xylan decreased while cellulose was only slightly affected in all experiments. It was also found that the smaller particle size is better for ozonolysis. The similar water activity of the different optimum moisture contents for ozonolysis reveals that the free and bound water ratio is a key factor of ozonolysis. The best result of ozonolysis was obtained at the mesh of −300 and the moisture of 60%, where up to 75% lignin was removed. The glucose yield after enzymatic hydrolysis increased from 18.5% to 80%. Water washing had low impact on glucose yield (less than 10% increases), but significantly reduced xylose yield (up to 42% decreases). The result indicates that ozonolysis leads to xylan solubilization.

Sugarcane bagasse ozonolysis pretreatment: Effect on enzymatic digestibility and inhibitory compound formation

Sugarcane bagasse was pretreated with ozone to increase lignocellulosic material digestibility. Bagasse was ozonated in a fixed bed reactor at room temperature, and the effect of the two major parameters, ozone concentration and sample moisture, was studied. Acid insoluble and total lignin decreased whereas acid soluble lignin increased in all experiments. Pretreatment barely attacked carbohydrates, with cellulose and xylan recovery rates being >92%. Ozonolysis increased fermentable carbohydrate release considerably during enzymatic hydrolysis. Glucose and xylose yields increased from 6.64% and 2.05%, for raw bagasse, to 41.79% and 52.44% under the best experimental conditions. Only xylitol, lactic, formic and acetic acid degradation compounds were found, with neither furfural nor HMF (5-hydroxymethylfurfural) being detected. Washing detoxification provided inhibitor removal percentages above 85%, increasing glucose hydrolysis, but decreasing xylose yield by xylan solubilization. SEM analysis showed structural changes after ozonization and washing.

Effect of ozonolysis pretreatment on enzymatic digestibility of wheat and rye straw

Wheat and rye straws were pretreated with ozone to increase the enzymatic hydrolysis extent of potentially fermentable sugars. Through a 2 5–1 factorial design, this work studies the influence of five operating parameters (moisture content, particle size, ozone concentration, type of biomass and air/ozone flow rate) on ozonization pretreatment of straw in a fixed bed reactor under room conditions. The acid insoluble lignin content of the biomass was reduced in all experiments involving hemicellulose degradation. Near negligible losses of cellulose were observed. Enzymatic hydrolysis yields of up to 88.6% and 57% were obtained compared to 29% and 16% in non-ozonated wheat and rye straw respectively. Moisture content and type of biomass showed the most significant effects on ozonolysis. Additionally, ozonolysis experiments in basic medium with sodium hydroxide evidenced a reduction in solubilization and/or degradation of lignin and reliable cellulose and hemicellulose degradation.

Ozone modulation of volatile hydrocarbons using membrane introduction mass spectrometry.

A new method that we describe as chemical modulation of volatile hydrocarbons is investigated using ozonolysis pretreatment and membrane introduction mass spectrometry (MIMS). This extension to the MIMS technique is intended to enhance the selectivity of MIMS for measuring hydrocarbons in the complex mixtures often encountered in polluted air samples. The test samples for this study were dilute (parts per billion by volume, ppbv) two-component hydrocarbon mixtures in synthetic air. Ozone reacted to completely suppress the MIMS signal from beta-pinene in a mixture of toluene and beta-pinene and the MIMS signal from cyclohexene in a mixture of cyclohexene and cyclohexane. As expected, the ozone reaction produced little attenuation of the MIMS signal from toluene and cyclohexane in the test mixtures. The basis of the method is that the products of the ozonolysis, which is rapid for alkenes, are polar compounds that are excluded by the membrane used here, as confirmed in this study. Since the modulation only affects unsaturated hydrocarbons (and other similar organic compounds), the method can be used to aid in quantitative analysis of volatile hydrocarbon compounds in air samples for air pollution monitoring.