Search

Published in Chemical Papers. Full-text access:https://rdcu.be/cZGaK

Published in Chemical Engineering Communications. Free download:https://www.tandfonline.com/eprint/B7FWW5F8EAGD4ZMEKYK4/full?target=10.1080/00986445.2022.2116325

Published in Separation Science and Technology. Free download:https://www.tandfonline.com/eprint/53FUC2EGMEBGGK2E6SWU/full?target=10.1080/01496395.2022.2097093

Published in Separation Science and Technology. https://doi.org/10.1080/01496395.2023.2167662 Free download:https://www.tandfonline.com/eprint/GSFX59RF3XGIMUQPGTNN/full?target=10.1080/01496395.2023.2167662

Published in Industrial & Engineering Chemistry Research. https://doi.org/10.1021/acs.iecr.2c03799

The Radke-Prausnitz model, a typical three-parameter model belonging to the Langmuir-Freundlich-type equation, is increasingly being used to correlate the equilibrium data of various adsorption processes. However, very few published works provide the correct information on (1) the nonlinear form of this model, (2) the units of its parameters, and (3) its original citation. This work provides a critical analysis of the Radke-Prausnitz model with special emphasis on promoting its proper application in adsorption research. The correct expression and citation of the models used in adsorption studies are provided. The correct units of its parameters aRP, bRP, and β are L/kg, (mol/kg)/(mol/L)β, and unitless when the solution phase concentration Ce is given in mol/L and the adsorbed phase concentration qe is defined in mol/kg. The Radke-Prausnitz model can be reduced to the Henry, Freundlich, Langmuir, or Redlich-Peterson model in some special cases. The Radke - Prausnitz model is valid when the exponent β is in the range of 0≤β≤1. A new adsorption equilibrium constant of this model is introduced. The feasibility of using the new equilibrium constant to calculate the thermodynamic parameters (ΔG°, ΔH°, and ΔS°) of adsorption processes is discussed herein.

Article published in Industrial & Engineering Chemistry Research. Free download:https://pubs.acs.org/articlesonrequest/AOR-MC67TWM4RV9MVEIGBJCP

Published in Chemical Engineering Science. Free Download (beforeOctober 16, 2022):https://authors.elsevier.com/c/1ff2G26dbwuNE

The popularity of heat drying of wastewater sludge has increased over the past several years because it can reduce sludge mass and volume, and hence disposal costs. However, drying sludge using conventional combustion-heated dryers is energy-intensive. Heat pump dryers can be efficient and offer significant energy savings by recycling the drying heat. This paper describes a heat pump dryer designed for continuous drying of industrial wastewater sludge. The dryer constructed was essentially a closed-loop air system. The air used for drying is dehumidified to recover the latent heat of vaporization, re-heated using the recovered heat, and recirculated in a closed environment. The closed-loop layout eliminates emissions of dust, malodorous gases, and volatile compounds, obviating the need for exhaust treatment otherwise required to meet environmental regulations. Data on the moisture extraction rate, specific moisture extraction rate, and specific energy consumption are presented and discussed.

Published in Journal of Environmental Chemical Engineering. Free download:https://authors.elsevier.com/c/1fMKP_oKrieR8v

Experimental equilibrium data for the adsorption of water contaminants on solid surfaces are generally correlated using suitable isotherm expressions. In most cases, adsorption isotherms are used empirically with the primary aim of finding the best fitting ones. The literature of adsorptive water decontamination is replete with such isotherm comparisons, usually evaluated on the basis of some statistical metrics such as R2 and RMSE. For example, several studies have compared and ranked the isotherm equations of Hill, Sips, Koble–Corrigan, and Liu. These comparative evaluations imply that the four isotherms possess different data fitting abilities, and consequently it is possible to identify the most accurate one. The present study argues that this commonly held notion is incorrect. It demonstrates that the four isotherms provide the same results when fitted to three previously published data sets. This finding suggests that the four isotherms are mathematically equivalent despite apparent differences in their formulations. Indeed, a mathematical analysis unequivocally shows that the Hill, Sips, Koble–Corrigan, and Liu isotherms can be represented by a single generic equation with three arbitrary fitting parameters. As such, the four isotherms must provide exactly the same fit to a given set of isotherm data.

Published in Separation & Purification Reviews. Free download:https://www.tandfonline.com/eprint/UXY6MUTFZX4YT2TGKM5N/full?target=10.1080/15422119.2022.2039196

Published in Separation and Purification Technology. Free download:https://authors.elsevier.com/a/1ghmT4wbrTBXso

Published in Journal of Molecular Liquids. Free download:https://authors.elsevier.com/a/1gI~1c8qpWkDv

Several theoretical and empirical models are available to correlate experimental breakthrough curves of water pollutants, one of which is the two-parameter Belter model. Although not as well known as the century-old Bohart–Adams model, the Belter model is being used with sufficient frequency to merit wider awareness of its strengths and weaknesses. Through a systematic analysis, it is shown that the two adjustable parameters of the Belter model are analogous to the equilibrium capacity and rate parameters of the Bohart–Adams model. Breakthrough curves predicted by the Belter model are perfectly symmetric because their inflection points are invariant and always correspond to the midpoint of the curves. As a consequence, the Belter model provides poor fits to asymmetric breakthrough curves. In this work, an improved version of the Belter model is introduced. The new model with a floating inflection point manifests excellent conformity with mildly and, more importantly, severely asymmetric breakthrough curves.

A simple method is presented for extracting pore diffusion coefficients from batch adsorption kinetic data. The method employs the classic Langmuir kinetics model which is characterized by a single rate coefficient. An analytical solution in the form of a simple algebraic equation is available for this rate model. Fitting the algebraic equation to batch kinetic data to determine the rate coefficient is straightforward and can be conveniently accomplished using standard spreadsheet programs. The resultant rate coefficient can be converted to the pertinent pore diffusion coefficient via a separate algebraic expression. The proposed modeling approach provides accurate fits of experimental kinetic data taken from the literature and yields acceptable errors in the best estimates for pore diffusion coefficients. Specific examples discussed are the adsorption of fluoride by bone char and laterite adsorbents.

This paper reports the use of five probability cumulative distribution functions (normal, log-normal, logistic, Gompertz, and Weibull) to correlate published breakthrough data of water and air contaminants (ciprofloxacin, ammonium, hydrogen chloride, and hydrogen sulfide). Because the shape of the ciprofloxacin breakthrough curve is fairly symmetric, it is well correlated by all five functions (R2 > 0.99). They also provide a good representation of the overall shape of the ammonium breakthrough curve (R2 > 0.99). However, none can describe the leakage of ammonium during the initial period of column operation. The log-normal and Weibull functions give an excellent representation of the tailing HCl data while the normal, logistic, and Gompertz functions are quite poor. This difference in performance can be explained by the different characteristics of their inflection points. The log-normal and Weibull functions have a floating inflection point, which gives them flexibility in tracing the shape of the tailing data. The invariant inflection points of the normal, logistic, and Gompertz curves restrict their data fitting ability. Only the log-normal function can provide a reasonable fit to the H2S data with strong tailing. It is shown that the invariant inflection point of a probability function can be converted to a floating one. A version of the Gompertz function so modified provides a good quantitative correlation of the tailing data of H2S (R2 = 0.99).

A research topic of current interest concerns the measurement and modeling of adsorption isotherms of water contaminants. The bulk of measured equilibrium isotherms exhibit the convex-upward or favorable curve shape, which can be described by the two-parameter Hill-Langmuir and Freundlich isotherms. An increasing number of recent studies have however reported S-shaped or sigmoidal equilibrium isotherms. Modeling such equilibrium data requires the use of isotherm equations with a highly flexible functional form. This work introduces a little-known isotherm useful for tracking the trajectory of S-shaped equilibrium data. This relatively simple three-parameter isotherm, first proposed by Krishnamurti in 1951, has theoretical merit because it is based on a co-operative adsorption mechanism. It is shown that previously reported S-shaped equilibrium data of water contaminants can be represented by the Krishnamurti isotherm. Specific examples discussed are (1) ammonium ion adsorption by the clay mineral sepiolite, (2) uptake of the antibiotic ciprofloxacin by a magnetic nanosorbent, and (3) fluoride ion removal by a layered double hydroxide adsorbent. Additionally, it is found that a modified form of the Krishnamurti isotherm is superior to its original counterpart. The original and modified Krishnamurti isotherms can be practically very useful to describe S-shaped equilibrium data and for adsorptive process modeling.

The BET equation is commonly used to describe type II sigmoid isotherms of water contaminants. However, there are some type II isotherms that do not agree with the BET equation. In this paper, three modified BET equations (Aguerre–Suarez–Viollaz, Pantuso–Tolaba–Aguerre, and Aranovich–Donohue) are evaluated against published isotherm data of dysprosium, reactive blue 5G, and naphthenic acid. In the cases studied, the three modified BET equations are shown to outperform the original BET equation. The Aranovich–Donohue equation is a promising isotherm model, offering accurate data correlations and statistically significant parameter estimates. In particular, it is very effective in tracing the atypical curve shapes of the reactive blue 5G and naphthenic acid isotherms. Although the Aranovich–Donohue equation has not attracted much attention, it is a practical alternative to the widely used BET equation for correlating adsorption isotherms of water contaminants.

Equilibrium data for aqueous adsorption systems are often correlated using isotherm models originally developed for adsorption at the gas-solid interface. A prominent example is the Langmuir isotherm, which has been used in thousands of investigations to describe the adsorption of dissolved substances at the liquid-solid interface. Another example is the Kiselev isotherm, which was proposed to account for adsorption at the gas-solid interface when adsorbate-adsorbate interactions are significant. Researchers who have applied the Kiselev isotherm to adsorption data for liquid-solid systems were puzzled by the fact that data fittings in most cases returned negative values for the adsorbate-adsorbate association equilibrium constant. It is shown in the present study that the data fitting problem is a direct consequence of misusing the Kiselev isotherm. In all previous studies, the Kiselev isotherm was used to fit type I isotherm data. Because the concept of adsorbate-adsorbate interactions is incompatible with a type I isotherm, fitting the Kiselev isotherm to such data can lead to nonsensical parameter estimates. The Kiselev isotherm was devised to account for type V isotherms exhibiting a sigmoid or S-shaped data trend. Physically meaningful parameter estimates can be obtained if the Kiselev isotherm is applied to type V isotherm data.

Breakthrough curves of water contaminants are usually analyzed using simple fixed bed models such as the Bohart-Adams, Thomas, and Yoon-Nelson equations, which are by design symmetric. Because breakthrough data often follow an asymmetric pattern, the use of models that do not account for asymmetry could lead to poor fits, consequently resulting in erroneous estimates of breakthrough and exhaustion times. To address this issue, the Bohart-Adams, Thomas, and Yoon-Nelson models were modified by a logarithmic transformation to enhance their data fitting ability. The three modified models were found capable of providing robust fits to seven separate sets of previously reported asymmetric breakthrough data of water contaminants (fluoride, methylene blue, salicylic acid, lead, mercury, nickel, and arsenic), with reported residual root mean square error (RRMSE) values ranging from 0.019 to 0.046. In consequence, the new models were found capable of providing reliable estimates of breakthrough and exhaustion times corresponding to any predetermined concentration level. By contrast, the three original models were found to perform poorly, reporting inferior RRMSE values ranging from 0.038 to 0.086 for data fits and providing grossly inaccurate estimates of breakthrough and exhaustion times. The new models contain only parameters that appear in the original models, and are highly flexible, being able to assume virtually all monotonically increasing sigmoid shapes. They represent a far more accurate alternative to the original models.

In a comment on my article [1] published in this journal, Hu and Zhang [2] assert that I had misinterpreted the Bohart-Adams equation derived by Amundson and that the Bohart-Adams equation lacks the bed voidage parameter. I argue that Hu and Zhang are wrong on both counts. I further contend that their version of the Bohart-Adams equation derived by Amundson contains a glaring error of a rudimentary nature.

Fixed bed adsorption studies often report asymmetric breakthrough curves which exhibit a tailing phenomenon as the effluent approaches the influent concentration. Evaluations of models capable of describing such curves are lacking in the literature. This paper examines the ability of the Gompertz equation to correlate asymmetric breakthrough data collated from reports published in the environmental adsorption literature. It is shown that the Gompertz equation, which has received little attention in this field of research, is able to track asymmetric breakthrough curves displaying a moderate degree of tailing. The logistic equation, which is mathematically analogous to the Bohart-Adams, Thomas, and Yoon-Nelson models, cannot effectively describe such asymmetric data. The Gompertz equation provides only an approximate representation of breakthrough data exhibiting a pronounced degree of tailing. To fit such data, this paper presents two modified forms of the Gompertz equation, which are shown to be highly accurate (R2 > 0.996). The Gompertz equation and the two modified versions are useful additions to the toolbox of breakthrough curve modeling which has long been filled with the Bohart-Adams, Thomas, and Yoon-Nelson models. These popular logistic-based equations are confined to fitting symmetric breakthrough curves.

This communication discusses the fixed bed modeling results of the recent paper published by Ang et al. (2020) in this journal.

Surface diffusion coefficients may be estimated by fitting solutions of a diffusion model to batch kinetic data. For non-linear systems, a numerical solution of the diffusion model’s governing equations is generally required. We report here the application of the classic Langmuir kinetics model to extract surface diffusion coefficients from batch kinetic data. The use of the Langmuir kinetics model in lieu of the conventional surface diffusion model allows derivation of an analytical expression. The parameter estimation procedure requires determining the Langmuir rate coefficient from which the pertinent surface diffusion coefficient is calculated. Surface diffusion coefficients within the 10−9 to 10−6 cm2/s range obtained by fitting the Langmuir kinetics model to experimental kinetic data taken from the literature are found to be consistent with the corresponding values obtained from the traditional surface diffusion model. The virtue of this simplified parameter estimation method is that it redu...

In the water and wastewater treatment field several simplistic models of packed bed dynamics such as the Bohart-Adams, Thomas, and Yoon-Nelson models are frequently used by investigators to fit adsorption breakthrough data. The century-old Bohart-Adams model is arguably the best known one which also serves as the foundation of the bed depth-service time equation. In recent years a substantial body of literature on the subject of fixed bed modeling has however claimed that it is inferior to other models. The present paper shows that such claims are incorrect and misleading because of biased comparisons in which the fitting ability of an oversimplified version of the Bohart-Adams model was compared with those of the Thomas and Yoon-Nelson models. The oversimplified Bohart-Adams equation is in effect an exponential function which predicts an exponentially increasing breakthrough value with time. As such, it is unable to fit typical breakthrough curves which are S-shaped or sigmoidal. It can be shown that a proper version of the Bohart-Adams model gives fit quality similar to those of the Thomas and Yoon-Nelson models. This is not unexpected since the three simplistic fixed bed models can be expressed in terms of the logistic equation of population growth; that is, mathematically they are equivalent.

Hydrogen is an expensive utility in refineries. To reduce costs and save energy, a hydrogen system should be not only optimally designed but also optimally operated. In this paper, a mathematical model is proposed for determining optimal operation of a hydrogen network. Changes in the hydrogen demand of a hydrogen sink are assumed to vary with changes in the operational load. In the proposed model, if there is no connection between a source and a sink, the corresponding flow rate will be set as zero. In this way, the model is a linear programming model. A case study shows that the model is effective and very easy to solve.

Adsorption is an important process for arsenic removal from drinking water supplies. Fixed bed column processes are the preferred mode of operation owing to their simplicity and proven performance. Mathematical models can facilitate the design and optimization of fixed bed adsorbers. For systems exhibiting linear isotherm behavior over the relevant concentration range, their performance can be predicted using models that are amenable to analytical solutions. The predictive utility of an asymptotic solution of the homogeneous surface diffusion model (HSDM) and an approximate solution of a linear driving force model (LDFM) under linear isotherm approximation was evaluated in this study. A previously published pilot test on arsenic breakthrough in a fixed bed adsorber of polymer-supported nanoparticles was modeled. Model parameters were estimated on the basis of some easily determined batch measurements. The pilot test yielded 27,000 bed volumes at 10 μg/L arsenic. The two analytical solutions predicted 24,200 and 27,100 bed volumes. Despite the simplicity of the HSDM and LDFM solutions, their predictions agreed well with the experimental data. These analytical solutions are very straightforward, easy to apply, and provide acceptable modeling power.

Introducing purification devices into hydrogen systems can enhance the extent of hydrogen reuse. However, the economic performance of a purification device depends on its appropriate placement within a hydrogen system. Based on some established graphical methods, this paper explores the influences of the feed concentration on the purification proces s . A simple and systematic graphical method is proposed for identifying the OPP (optimal purification process) by extending the well-known pinch technology method. The proposed method can determine the OPP with the minimum feed flow rate and minimum tail gas flow rate under the condition of maximizing the HUS (hydrogen utility savings). The corresponding feed streams of the OPP also can be identified easily in the purification polygon. Furthermore, the conception of minimum separation work is used to compare different purification processes. A realistic case study is used to illustrate the applicability of the proposed method. Three different scenarios are analyzed and the results show that notable reductions in the minimum separation work consumption can be achieved (22%, 34% and 16% for the three scenarios).

Two different model selection indices, the Akaike information criterion (AIC) and the coefficient of determination (R 2 ), are used to discriminate competing isotherm equations for aqueous pollutant removal systems. The former takes into account model accuracy and complexity while the latter considers model accuracy only. The five types of isotherm shape in the Brunauer-Deming-Deming-Teller (BDDT) classification are considered. Sorption equilibrium data taken from the literature were correlated using isotherm equations with fitting parameters ranging from two to five. For the isotherm shapes of types I (favorable) and III (unfavorable), the AIC favors two-parameter equations which can easily track these simple isotherm shapes with high accuracy. The R 2 indicator by contrast recommends isotherm equations with more than two parameters which can provide marginally better fits than two-parameter equations. To correlate the more intricate shapes of types II (multilayer), IV (two-plateau) and V (S-shaped) isotherms, both indices favor isotherm equations with more than two parameters.

In hydrogen networks, purifiers are quite often used to reduce operating costs. They should be properly integrated with the whole network in order to maximize the benefit. In this paper, a graphical method is proposed for targeting the minimum fresh resource consumption of hydrogen networks considering separation performance of purifiers. The material balance of the whole hydrogen network shows that the extent of fresh hydrogen reduction is subject to the maximum hydrogen surplus. Based on such observation, the mass transfer triangle is developed to describe the hydrogen transformation from maximum hydrogen surplus to fresh hydrogen. With both the purity and the flow rate of purification streams optimized, the minimum fresh hydrogen consumption can be determined through the proposed graphical method. Two cases are studied to illustrate the proposed methodology.

We have developed a process model to simulate the behavior of an industrial-scale pressurized Lurgi fixed-bed coal gasifier using Aspen Plus and General Algebraic Modeling System (GAMS). Reaction characteristics in the fixed-bed gasifier comprising four sequential reaction zones—drying, pyrolysis, combustion and gasification are respectively modeled. A non-linear programming (NLP) model is developed for the pyrolysis zone to estimate the products composition which includes char, coal gases and distillable liquids. A four-stage model with restricted equilibrium temperature is used to study the thermodynamic equilibrium characteristics and calculate the composition of syngas in the combustion and gasification zones. The thermodynamic analysis shows that the exergetic efficiency of the fixed-bed gasifier is mainly determined by the oxygen/coal ratio. The exergetic efficiency of the process will reach an optimum value of 78.3% when the oxygen/coal and steam/coal mass ratios are 0.14 and 0.80, respectively.

Centrifugal pumps are widely used in cooling water systems to transport cooling water to its users. They are installed in the header line of the feed pipe, constituting a main pump network. The pressure head of the main pumps must be large enough to satisfy the pressure heads of all coolers. The pressure drop of parallel branch pipes must be balanced by reducing the opening of valves for some coolers, incurring an energy penalty on some pumps. To attain energy savings, this paper proposes an auxiliary pump network whereby auxiliary pumps are installed in parallel branch pipes. A superstructure-based mathematical model is developed to optimize the total cost of the main and auxiliary pump networks. The optimal number of auxiliary pumps and their installation locations are determined by solving the model with a simulated annealing algorithm. The effectiveness of the model is tested by a case study based on the cooling water network of a refinery.

Introducing purification devices into hydrogen systems can enhance the extent of hydrogen reuse. The economic performance of a purification device depends on its appropriate placement within a hydrogen system. This work presents an improved version of a previously published graphical method for integrating purification processes in hydrogen systems. A mathematical method is deduced for calculating the maximum hydrogen utility savings potential of a hydrogen system with purification reuse. The improved graphical method is able to handle the constraints of concentration and flow rate of a purification process when targeting the maximum hydrogen utility savings. The proposed method can be used for analyzing purification processes with any feed concentration. The graphical method is tested on two case studies.

A new method based on the heat duty–time (Q–t) diagram is proposed for heat integration of heat exchanger networks featuring batch streams. Using the Q–t diagram method, the energy targets and the structure of the initial heat exchanger network can be easily obtained. The method can be used both for direct and indirect heat integration of batch streams. For indirect heat integration, the heat degradation of intermediate media is considered. A case study on optimizing the heat exchanger network of a hydrazine hydrate plant is used to illustrate the application of the method. The results show that integration of this heat exchanger network without considering its batch streams can limit the total energy savings.

Conventional cooling water networks usually operate in a parallel configuration. Converting a parallel design to a series arrangement can yield a significant reduction in fresh cooling water consumption because of water reuse. This paper presents a two-step methodology for retrofit design of cooling water networks. The proposed methodology can convert a parallel configuration to a series arrangement without investment in a new heat-transfer area. The series arrangement is assumed to contain two heat exchangers. The first heat exchanger in the series arrangement is designated as the supplier because it supplies reuse water to the second heat exchanger, which is called the receiver. To retrofit a cooling water network with a parallel arrangement of several heat exchangers, the first step of the methodology uses the concept of flow rate difference curve to classify the heat exchangers into the two categories of supplier and receiver. In the second step, receiver sensitivity graphs provide guidelines for syst...

Emergy synthesis is an energy-based evaluation method useful for investigating agroecosystems in the context of ecology and economics owing to its ability to express different types of inputs on a common basis: the solar energy. In this article, emergy synthesis is used to analyze, in quantitative terms, the agroecosystem in the area of Yan'an, which coexists with a mineral exploitation region in the Loess Plateau of China. The analysis indicates that the emergy input supporting the agroecosystem totaled 1.26E + 22 seJ/yr in 2006. On a percentage basis, renewable resources, nonrenewable resources, and purchased emergy accounted for, respectively, 36%, 31%, and 33% of the total emergy input. With 67% of its total emergy input derived from local resources (renewable and nonrenewable), the agroecosystem is indicative of a sustainable pattern of agricultural production. The environmental sustainability index for the agroecosystem was calculated to be 1.70. A comparative analysis indicates that Yan'an's agroec...

Setting heat pumps correctly in a chemical process system can enhance the energy utilization ratio of the system, reduce the consumption of both the hot and cold utilities, and achieve utility savings and economic benefits. In this paper, for the case of introducing a single heat pump into a system, the dynamic changes of the grand composite curve and pinch temperature under different scenarios are analyzed using a graphical analysis method. The reasons and conditions for such changes are determined. It is shown that for cases that exhibit a change in pinch temperature more hot and cold utility savings may be obtained by using two heat pumps. Existing as well as new two-heat-pump arrangements that comply with the cross-pinch rule are presented.

Emergy analysis is useful for evaluating the resource utilization and environmental performance of industrial systems. However, emergy analysis in its current state can produce erroneous results when it is applied to systems with feedback structure. It is shown that traditional emergy algebra, if not applied properly, can cause violations of the tenet of total inheritance, which is one of the core notions in emergy theory. To overcome this deficiency, this paper proposes a new concept, called virtual emergy flow, for calculating the emergy of feedback structures. The utility of the virtual emergy flow concept is illustrated by the emergy analyses of two different types of feedback structures commonly found in chemical process systems as well as by a case study based on a power and methanol multiproduct system.

Two types of waste paper materials, newspaper and office paper, were evaluated for their potential to be used as renewable feedstock for the production of fermentable sugars via the enzymatic hydrolysis of their cellulose fractions. The effects of four factors (hydrolysis time, enzyme loading, surfactant addition and phosphoric acid pretreatment) on the extent of sugar yield were assessed and quantified by using a methodical approach based on response surface methodology. The statistical experimental design used in this study requires fewer experimental runs compared to some commonly used experimental designs. In the newspaper hydrolysis case, response surface plots revealed that the degree of sugar release increased with an increase in hydrolysis time but it was hardly affected by the enzyme loading and acid pretreatment factors. The surfactant addition factor exhibited a positive effect when the enzyme loading level was relatively low. With office paper as the substrate, three of the four factors (hydrolysis time, enzyme loading and acid pretreatment) exhibited positive effects on the extent of sugar release. At local optimum conditions, the maximum sugar yield from office paper was found to be 0.82 g of reducing sugars per gram of paper, which was about 4.8 times higher than the maximum sugar release from the newspaper substrate.