Fractal Kinetics Research Articles

Enzymatic hydrolysis of highly concentrated substrates obtained from Miscanthus giganteus

This work is the first to study the enzymatic hydrolysis of four types of substrates obtained from Miscanthus giganteus of the KAMIS variety of Russian breeding. The study was conducting using the authors’ methodology based on a chemical pretreatment of substrates at atmospheric pressure with HNO3 and NaOH dilute solutions. A one-stage pretreatment of Miscanthus giganteus allows the polysaccharide content to be increased up to 90.4–90.8%, compared to 98.3–99.4% following a two-stage treatment. The experimental results of enzymatic hydrolysis of the four obtained substrates in the range of initial concentrations from 30 to 120 g/l are approximated using fractal kinetics approaches. An increase in the initial substrate concentrations in the specified range leads to an increase in the initial hydrolysis rate by 2.8–3.3 times and a decrease in the yield of reducing sugars by 12.4–13.1%. All four pretreatment types turned out to be extremely effective for Miscanthus giganteus, ensuring an increase in the reactivity to enzymatic hydrolysis by 34–36 times compared to the starting raw material. Lowered yields of reducing sugars are observed during enzymatic hydrolysis of the alkaline delignification product of Miscanthus giganteus, which is associated with the resistance of Miscanthus giganteus to treatment with sodium hydroxide. An increase in the initial concentration of substrates from 60 to 90 g/l does not lead to a significant decrease in the yield of reducing sugars. Therefore, enzymatic hydrolysis of highly concentrated substrates can be successfully used to produce biofuels and biochemicals.

The Influence of Environmental Temperature on the Passive Oxidation Process in the C/SiC Composite

The C/SiC composite plays a crucial role in providing thermal protection for hypersonic vehicles. The SiO2 oxide layer formed via passive oxidation during ablation constitutes a typical porous medium with self-similarity. Given its significant impact on the thermal protection of the material, accurately predicting the variation in the SiO2 oxide layer thickness is of paramount importance. The growth of the oxide layer impedes the diffusion of oxygen within the material. This study considered microstructural parameters of the oxide layer based on high-temperature gas oxidation tests of the C/SiC composite. Fractal theory was utilized to construct a fractal diffusion-reaction kinetics model describing oxygen diffusion within the oxide layer and the evolution of the oxide layer under varying environmental conditions. The finding demonstrated that the existence of the oxide layer significantly influences the passive oxidation of the composite. This study underscored the significance of predicting the impact of environmental parameters on passive oxidation in the practical application of the C/SiC composite and the study result offers a valuable reference for evaluating the thermal resistance of the C/SiC composite.

Effects of rock water with different acidity on microstructure and reburning ability of residual coal in goaf

To explore the influences of rock water acidity (PH = 4,5,7) over the microstructure and reburning behaviors of oxidized residual coal in the overlying goaf, the pore morphology, coal surface, functional group content and activity of pre-oxidized coal (O0) and water-immersed oxidized coal (OI) were analyzed by Low-temperature nitrogen adsorption and In-situ diffuse reflection experiments, combining with fractal dimension theory and functional group oxidation kinetics. The oxidation and reburning ability of coal samples has been analyzed by Thermogravimetric-Differential thermal analysis experiment. The results are as follows: Part of the type-III pores of pre-oxidized coal become type-II pores when immersed. The acidic solution has stronger corrosivity to O0 than distilled water, playing a role in smoothing coal and improving the uniformity of pore structure. The order of reburning ability of samples is OI7>OI4>O0>OI5 according to the ignition and stage average mass loss rate (RM). The reactivity of –OH may affect the reburning ability of coal more than its initial content. Soaking is beneficial to the decrease of activation energy of aliphatic groups, and the activity of –C=O- and -C-O- in acid-soaked coal molecules is stronger, so that they can take part in coal-oxygen composite reactions at low temperature.

Electrospherization of genistein@DNA core-shell nanospheres as a drug delivery system and theoretical study of the release mechanism

Encapsulation of poor water-soluble drug was considered as one of the widely used approaches to overcome such obstacle. The goal of this research was in situ encapsulate the hydrophobic genistein (GEN) during the electrospherization (Es) of deoxyribonucleic acid (DNA) nanospheres as a delivery system with appropriate drug release properties. The prepared nanospheres (free GEN sample; Es DNA and GEN loaded DNA; Es GEN@DNA) were characterized using uv–visible spectroscopy (UV–vis), transmission electron microscope (TEM), zeta potential, Fourier transform infrared spectroscopy (FTIR), x-ray diffraction analysis (XRD), and stability test. In addition, the drug encapsulation % was studied, the drug release efficiency was recorded and theoretically visualized to understand the mechanism and kinetics of GEN drug release. The results revealed that GEN was successfully encapsulated during the DNA electrospherization as a core (GEN)/shell (DNA) like structure with a wonderful stability against time. The UV–vis patterns and their deconvolutions introduced that the emerged peak around 372–500 nm of Es GEN@DNA nanospheres has an area under curve larger than that of the free GEN sample. Zeta potential value decreased from −17.4 to −14.3 mV. In addition, TEM images confirmed the formation of a core/shell structure with average size 109.2 nm. XRD pattern of Es GEN@DNA revealed that GEN lost its crystalline phase, which indicated the incorporation of the drug. On the other hand, %Encapsulation of GEN within DNA nanospheres was found to be 89.62%. Es GEN@DNA release profile explored that the well entrapped GEN within the DNA nanospheres could be a promising for sustained drug release. Besides, the dilemma of using a fractal or fractional kinetics model was overcame by introducing a general fractional kinetic equation that involves a time-dependent rate coefficient, which introduced that the solution of the fractional kinetic model can fit the release data profiles.

Hybrid approaches based on hydrodynamic cavitation, peroxymonosulfate and UVC irradiation for treatment of organic pollutants: fractal like kinetics, modeling and process optimization.

Hydrodynamic cavitation (HC) was emerged as one of the most potential technologies for industrial-scale wastewater or water treatment. In this work, a combined system of HC, peroxymonosulfate (PMS) and UVC irradiation (HC - PMS - UVC) was constructed for effective degradation of carbamazepine. The effect of several experimental parameters and conditions on the carbamazepine degradation was considered. The results show that the degradation and mineralization rates increases with an increase in the inlet pressure from 1.3 to 4.3 bars. The rates of carbamazepine degradation with the combined processes of HC - PMS - UVC, HC - PMS, HC - UVC, and UVC - PMS were 73%, 67%, 40% and 31%, respectively. Under the optimal conditions of reactor, the carbamazepine degradation and mineralization rates were 73% with 59%, respectively. The kinetics of carbamazepine degradation was studied applying a fractal-like approach. So, a new model was proposed by combining first order kinetics model and fractal-like concept. The obtained results show that the proposed fractal-like model gives a better performance compared with traditional first order kinetics model. It has been demonstrated that the HC - PMS - UVC process is a potential treatment method to destroy pharmaceutical pollutants from water and wastewater sources.

Fractal Kinetic Implementation in Population Pharmacokinetic Modeling.

Compartment modeling is a widely accepted technique in the field of pharmacokinetic analysis. However, conventional compartment modeling is performed under a homogeneity assumption that is not a naturally occurring condition. Since the assumption lacks physiological considerations, the respective modeling approach has been questioned, as novel drugs are increasingly characterized by physiological or physical features. Alternative approaches have focused on fractal kinetics, but evaluations of their application are lacking. Thus, in this study, a simulation was performed to identify desirable fractal-kinetics applications in conventional modeling. Visible changes in the profiles were then investigated. Five cases of finalized population models were collected for implementation. For model diagnosis, the objective function value (OFV), Akaike's information criterion (AIC), and corrected Akaike's information criterion (AICc) were used as performance metrics, and the goodness of fit (GOF), visual predictive check (VPC), and normalized prediction distribution error (NPDE) were used as visual diagnostics. In most cases, model performance was enhanced by the fractal rate, as shown in a simulation study. The necessary parameters of the fractal rate in the model varied and were successfully estimated between 0 and 1. GOF, VPC, and NPDE diagnostics show that models with the fractal rate described the data well and were robust. In the simulation study, the fractal absorption process was, therefore, chosen for testing. In the estimation study, the rate application yielded improved performance and good prediction-observation agreement in early sampling points, and did not cause a large shift in the original estimation results. Thus, the fractal rate yielded explainable parameters by setting only the heterogeneity exponent, which reflects true physiological behavior well. This approach can be expected to provide useful insights in pharmacological decision making.

Conversion of biomass to biofuels through sugar platform: A review of enzymatic hydrolysis highlighting the trade-off between product and substrate inhibitions

Specific combinations of enzymes depolymerize lignocellulosic biomass into respective monomers following various complex kinetic pathways. Conversion of biomass to biofuel through sugar platform is substantiated with specific kinetics controlling enzymatic hydrolysis in presence of unavoidable inhibitors. Some amount of lignin, still present in the delignified biomass broth acts as a substrate inhibitor for the specific group of cellulolytic enzymes during hydrolysis. Considering state-of-the-art research works, biomass to enzyme ratio is highlighted as one of the key factors in biomass hydrolysis, followed by time and agitation speed. Correlations between various kinetic parameters and different process variables are analysed in-depth using experimental outcomes as well as model predictions. Role of process parameters on hydrolysis outcomes, highlighting specific inhibition kinetics, deactivation of enzymes, and effect of mechanical agitation, is discussed thoroughly. Fractal kinetics and optimum product inhibition are also reviewed on a comparative basis. In order to understand the role of specific oligosaccharides on inhibition, the effects of mobility of sugar molecules, enzymatic trans-glycosylation, modes of hydrolysis (batch or fed-batch) on sugar yield are elaborated with respect to monomeric sugar supplements. Most research works have strong evidences to support that addition of other monosaccharides (excluding the end products) like glucose, galactose, mannose, fructose, of similar concentration, lowers the glucose yield to different degrees. Supplements of monomeric sugars, except xylose, increase the Michaelis-Menten [MM] constant, showing a reduced affinity of enzymes towards the substrate, through the competitive mode of inhibition. Xylose, however, exhibits a non-competitive type inhibition, through a strong affinity for the enzyme, enzyme-substrate, and enzyme-cellobiose complex. Most of the researchers focus on the removal of glucose as a primary end product in order to abate inhibition, except some periodically removed cellobiose. Cellobiohydrolase alone can generate cellobiose much more than endoglucanase alone. The synergistic action of different cellulolytic enzymes is found beneficial in terms of sugar generation. Product inhibition remains a crucial factor that needs to be overcome in order to attain a higher concentration of specific mono sugars.

Why Should the Reaction Order of a Bimolecular Reaction be 2.33 Instead of 2?

Predicting the reaction kinetics, that is, how fast a reaction can happen in a solution, is essential information for many processes, such as industrial chemical manufacturing, refining, synthesis and separation of petroleum products, environmental processes in air and water, biological reactions in cells, biosensing, and drug delivery. Collision theory was originally developed to explain the reaction kinetics of gas reactions with no dilution. For a reaction in a diluted inert gas solution or a diluted liquid solution, diffusion often dominates the collision process. Thus, it is necessary to include diffusion in such a calculation. Traditionally, the classical Smoluchowski rate is used as a starting point to predict the collision frequency of two molecules in a diluted solution. In this report, a different collision model is derived from the adsorption of molecules on a flat surface. A surprising result is obtained, showing that the reaction order for bimolecular reactions should be 2 and 1/3 instead of 2, following a fractal reaction kinetics.

Critical time-dependent branching process modelling epidemic spreading with containment measures* *This work celebrates the 70th birthday of our dear friend and colleague Bob Ziff.

During the COVID pandemic, periods of exponential growth of the disease have been mitigated by containment measures that in different occasions have resulted in a power-law growth of the number of cases. The first observation of such behaviour has been obtained from 2020 late spring data coming from China by Ziff and Ziff in reference Ziff and Ziff (2020 Fractal kinetics of COVID-19 pandemic MedRxiv). After this important observation the power-law scaling (albeit with different exponents) has also been observed in other countries during periods of containment of the spread. Early interpretations of these results suggest that this phenomenon might be due to spatial effects of the spread. Here we show that temporal modulations of infectivity of individuals due to containment measures can also cause power-law growth of the number of cases over time. To this end we propose a stochastic well-mixed susceptible-infected-removed model of epidemic spreading in presence of containment measures resulting in a time dependent infectivity and we explore the statistical properties of the resulting branching process at criticality. We show that at criticality it is possible to observe power-law growth of the number of cases with exponents ranging between one and two. Our asymptotic analytical results are confirmed by extensive Monte Carlo simulations. Although these results do not exclude that spatial effects might be important in modulating the power-law growth of the number of cases at criticality, this work shows that even well-mixed populations may already feature non trivial power-law exponents at criticality.

The Influence of Silver Nanoparticle Form on the Toxicity in Freshwater Mussels

The contribution of the form of silver nanomaterials (nAg) towards toxicity in aquatic organisms is not well understood. The purpose of this study was to examine the toxicity of various structures (sphere, cube and prism) of nAg in Dreissena bugensis mussels. Mussels were exposed to increasing concentrations of polyvinyl-coated nAg of the same size for 96 h at 15 °C. They were then analyzed for biophysical changes in the cytoplasm (viscosity, protein aggregation and lipids), neuro-activity (fractal kinetics of acetylcholinesterase (AChE)), oxidative stress (labile zinc (Zn) and lipid peroxidation) and inflammation (arachidonate cyclooxygenase). Although some decreasing effects in protein aggregation were observed, viscosity was more strongly decreased in mussels exposed to spheric and prismatic nAg. The activity of AChE was significantly decreased in the following form-dependent manner: prismatic > cubic > spheric nAg. The fractal dimension of AChE reactions was reduced by all geometries of nAg, while dissolved Ag had no effects. For nanoparticles with the same coating and relative size, spheric nAg produced more significant changes towards the fractal dimension of AChE, while prismatic nAg increased both protein aggregation and viscosity, whereas cubic nAg decreased protein aggregation in the cytoplasm. It is concluded that the geometries of nanoparticles could influence toxicity in aquatic organisms.

Interpreting airborne pandemics spreading using fractal kinetics’ principles

Introduction The reaction between susceptible and infected subjects has been studied under the well-mixed hypothesis for almost a century. Here, we present a consistent analysis for a not well-mixed system using fractal kinetics’ principles. Methods We analyzed COVID-19 data to get insights on the disease spreading in absence/presence of preventive measures. We derived a three-parameter model and show that the “fractal” exponent h of time larger than unity can capture the impact of preventive measures affecting population mobility. Results The h=1 case, which is a power of time model, accurately describes the situation without such measures in line with a herd immunity policy. The pandemic spread in four model countries (France, Greece, Italy and Spain) for the first 10 months has gone through four stages: stages 1 and 3 with limited to no measures, stages 2 and 4 with varying lockdown conditions. For each stage and country two or three model parameters have been determined using appropriate fitting procedures. The fractal kinetics model was found to be more akin to real life. Conclusion Model predictions and their implications lead to the conclusion that the fractal kinetics model can be used as a prototype for the analysis of all contagious airborne pandemics.

Kinetics of low radioactive wastewater imbibition and radionuclides sorption in partially saturated ternary-binder mortar

This study seeks to assess the imbibition kinetics of low radioactive wastewater (from the DayaBay nuclear power plant) into a partially saturated ternary-binder mortar, as well as the sorption kinetics of 60Co and 137Cs from the water. Mortar samples with the initial saturation degrees of 0, 0.4, 0.6, 0.8 and 1.0 were prepared for the wastewater treatment. Pore structure of the mortar was characterized using water vapor sorption isotherm and mercury intrusion porosimetry tests interpreted by the Guggenheim-Anderson-de Boer isothermal equilibrium, and volume- and energy-based fractal models. Results show that the mortar has consistent fractal pore structure between the models, and the liquid imbibitions follow the fractal imbibition kinetics, in which the parameters are non-linearly impacted by the initial saturation degrees. The sorption rate and retention capacity of 137Cs are much lower than those of 60Co, and both follow the Brouers–Sotolongo fractional kinetics. The findings uncover the complex liquid imbibition and radionuclides sorption kinetics in cement-based porous materials, and the in-situ data would contribute to the material designs and sorption controls for large scale in-situ treatments of wastewater from nuclear power plant.

Tea Bag Index to Assess Carbon Decomposition Rate in Cranberry Agroecosystems

In cranberry production systems, stands are covered by 1–5 cm of sand every 2–5 years to stimulate plant growth, resulting in alternate layers of sand and litter in soil upper layers. However, almost intact twigs and leaves remain in subsurface layers, indicating a slow decomposition rate. The Tea Bag Index (TBI) provides an internationally standardized methodology to compare litter decomposition rates (k) and stabilization (S) among terrestrial ecosystems. However, TBI parameters may be altered by time-dependent changes in the contact between litter and their immediate environment. The aims of this study were to determine the TBI of cranberry agroecosystems and compare it to the TBI of other terrestrial ecosystems. Litters were standardized green tea, standardized rooibos tea, and cranberry residues collected on the plantation floor. Litter decomposition was monitored during two consecutive years. Added N did not affect TBI parameters (k and S) due to possible N leaching and strong acidic soil condition. Decomposition rates (k) averaged (mean ± SD) 9.7 × 10−3 day−1 ± 1.6 × 10−3 for green tea, 3.3 × 10−3 day−1 ± 0.8 × 10−5 for rooibos tea, and 0.4 × 10−3 day−1 ± 0.86 × 10−3 for cranberry residues due to large differences in biochemical composition and tissue structure. The TBI decomposition rate (k) was 0.006 day−1 ± 0.002 in the low range among terrestrial ecosystems, and the stabilization factor (S) was 0.28 ± 0.08, indicating high potential for carbon accumulation in cranberry agroecosystems. Decomposition rates of tea litters were reduced by fractal coefficients of 0.6 for green tea and 0.4 for rooibos tea, indicating protection mechanisms building up with time in the tea bags. While the computation of the TBI stabilization factor may be biased because the green tea was not fully decomposed, fractal kinetics could be used as additional index to compare agroecosystems.

Interpreting airborne pandemics spreading using fractal kinetics'principles.

Introduction The reaction between susceptible and infected subjects has been studied under the well-mixed hypothesis for almost a century. Here, we present a consistent analysis for a not well-mixed system using fractal kinetics'principles. Methods We analyzed COVID-19 data to get insights on the disease spreading in absence/presence of preventive measures.We deriveda three-parameter model and show that the "fractal" exponenthof time larger than unity can capture the impact of preventive measures affecting population mobility. Results Theh=1 case, which is a power of time model, accurately describes the situation without such measures in line with a herd immunity policy.The pandemic spread in four model countries (France, Greece, Italy and Spain) for the first 10 months has gone throughfourstages: stages 1 and 3 with limited to no measures, stages 2 and 4 with varying lockdown conditions. Foreach stage and country two or three model parameters have been determined using appropriate fitting procedures. The fractal kinetics model was found to be more akin to real life. Conclusion Model predictions and their implications lead to the conclusion that the fractal kinetics model can be used as a prototype for the analysis of all contagious airborne pandemics.

Construction of a structural enzyme adsorption/kinetics model to elucidate additives associated lignin-cellulase interactions in complex bioconversion system.

Enzymatic hydrolysis is a rate-limiting process in lignocellulose biorefinery. The reaction involves complex enzyme-substrate and enzyme-lignin interactions in both liquid and solid phases, and has not been well characterized numerically. In this study, a kinetic model was developed to incorporate dynamic enzyme adsorption and product inhibition parameters into hydrolysis simulation. The enzyme adsorption coefficients obtained from Langmuir isotherm were fed dynamically into first-order kinetics for simulating the equilibrium enzyme adsorption in hydrolysis. A fractal and product inhibition kinetics was introduced and successfully applied to improve the simulation accuracy on adsorbed enzyme and glucose concentrations at different enzyme loadings, lignin contents, and in the presence of bovine serum albumin (BSA) and lysozyme. The model provided numerical proof quantifying the beneficial effects of both additives, which improved the hydrolysis rate by reducing the nonproductive adsorption of enzyme on lignin. The hydrolysis rate coefficient and fractal exponent both increased with increasing enzyme loadings, and lignin inhibition exhibited with increasing fractal exponent. Compared with BSA, the addition of lysozyme exhibited higher hydrolysis rates, which was reflected in the larger hydrolysis rate coefficients and smaller fractal exponents in the simulation. The model provides new insights to support process development, control, and optimization.

SIMULATION OF KINETIC CURVES OF THERMO-OXIDATIVE DESTRUCTION OF PROLIMERS USING DIFFERENTIAL EQUATIONS OF FRACTIONAL ORDER

In the paper it is proposed to consider fractal kinetics equations for process of thermo-oxidative destruction of melt polymers in the form of differential equations of fractional order, equaling to fraction of reactant groups of polymer, which are not subjected to destruction, with order of reaction n > 1. Small νd characterize the autoslowed-down type of reaction, and at big νd <1 - the autoaccelerated thermooxidation type with an decreasing speed of oxidation reaction, respectively much more smaller and close to an integer derivative on time of the first order. Comparative analysis of calculation results with corresponding results obtained by differential equations of integer order and degree of their matching with experimental data is given. Keywords: Fractal analysis, thermo-oxidative destruction, auto-slow and auto-accelerated type of thermal oxidation, differential equations of type and fractional orders.

Fractal kinetics for sorption of Methylene blue dye at the interface of Alginate Fullers earth composite beads

The present work highlights the kinetics of sorption of Methylene blue dye (MB) through Alginate-Fuller's earth (ALFE) composite bead interface using the fractal approach. The ALFE beads were characterized using FESEM, FTIR, and BET surface analysis studies. The specific surface area and pore volume of the ALFE beads as obtained by BET analysis are 11.6412 m2/g, and 3.2953 cm3/g respectively indicating mesoporosity. Montmorillonite was found to be the major component of Fullers earth from XRD analysis. The bead's adsorption efficiency was optimized for different experimental conditions like pH, adsorbent dosage, MB concentration, and contact time. The adsorption data was found to fit well using the Freundlich and modified Langmuir- Freundlich adsorption isotherm model, thereby reflecting the adsorbent's energetically heterogeneous surface. The heterogeneity exponent 'h' was more than zero, thereby proving the fractal approach to be more appropriate for explaining sorption's kinetics. The time-dependant pseudo first order instantaneous rate coefficient kinst,1 when plotted against the contact time showed a gradual decrease, thereby bringing out the presence of three different stages in the sorption process differing in their sites of sorption and also in the amount of MB sorbed. The ALFE beads were reusable, and the simulated kinetic data using the fractal approach could be instrumental in designing a continuous flow reactor in an MB dye treatment plant.

High yielding, one-step mechano-enzymatic hydrolysis of cellulose to cellulose nanocrystals without bulk solvent

Traditional methods of enzymatic hydrolysis of cellulose to cellulose nanocrystals (CNCs) are limited due to the low enzymatic efficiency and large amount of waste liquid. The purpose of this study is to improve the yield and production efficiency of CNCs by enzymatic hydrolysis. A one-step mechano-enzymatic hydrolysis method was developed by utilizing the synergy of wet grinding and enzymatic hydrolysis reaction to efficiently prepare CNCs. Under the optimal reaction conditions, the maximum CNCs yield of 49.3% was achieved with higher thermal stability and crystallinity index of 76.7%. Mechano-enzymatic hydrolysis followed the first order pseudo-kinetics, and fractal kinetics demonstrated that mechanical force of rotation speed affected the fractal dimensions and binding ability between substrate and enzyme. This study provides an alternative method to prepare CNCs, which can significantly avoid the use of bulk water, improve the production efficiency of CNCs and thus lower the production cost.

Kinetics of the exchange of water absorbed in silica hydrogel with ethanol: Modelling by brouers and sotolongo-costa fractal kinetics

Isothermal kinetics of the exchange of absorbed water in a silica hydrogel (SH) with ethanol was examined. The isothermal kinetic curves of absorbed water exchange with ethanol were measured at the temperatures: T = = 297, 306 and 316 K. The rate of the exchange was analysed as a function of time. The possibility of mathematical description of the kinetics of exchange by the Brouers and Sotolongo-Costa?s (BS) fractal?s kinetics model was examined. Parameter values (n, ?, ?) of the model and their changes with temperature were calculated. By applying the method of Ozao, it was determined that the rate limiting step of the process of exchange was the rate of exchange of the absorbed water with ethanol. Values of the fractal dimension of the SH-ethanol interphase were calculated. The dependences of the effective time-dependent rate coefficient, activation energy and pre-exponential factor on time and degree of exchange were calculated and discussed. The proposed model of the mechanism of the exchange of absorbed water with ethanol was discussed.

MgO nano-sheets for adsorption of anionic dyes from aqueous solution: Equilibrium and kinetics studies

MgO nano-sheets with a thickness of 26 nm and reticular structure were synthesized and characterized using FE-SEM, XRD, EDX and N2 adsorption/desorption. The synthesized MgO nano-sheets were used to remove two anionic dye pollutants (reactive orange and reactive yellow) from aqueous solution. The equilibrium and kinetics data were obtained, and fitted very well with Langmuir-Freundlich and Redlich-Peterson isotherms, and fractal like-pseudo second order kinetics model. The effect of solution pH and temperature on the removal efficiency of the synthesized adsorbent was studied in details. The maximum adsorption capacity of MgO nano-sheets to remove reactive orange is more than 30 times higher than reactive yellow. The difference in the adsorption mechanisms is proposed to explain such a noticeable difference in adsorption capacities of these dyes by MgO nano-sheets. The used MgO adsorbent can be regenerated completely using heat treatment in a furnace.