Zero-order Equations Research Articles

Application of TOPSIS algorithm in describing bacterial cellulose-based composite hydrogel performance in incorporating methylene blue as a model drug

A multi-component hydrogel was developed using bacterial cellulose, alginate, and gelatin with the aid of glycerol as trihydric alcohol which participates in re-distribution of hydrogen bonds in the test system. FTIR, XRD, SEM, and TGA as instrumental techniques were used to structurally characterize the physical/chemical properties of the formed composite hydrogel. By using an exponential equation, swelling behavior of the hydrogel was evaluated. By incorporating a model drug (methylene blue—MB) in the formed hydrogel, experiments were directed to study release characteristics of the MB where the medium solution for the release was prepared at four different pHs. The maximum cumulative drug release at pH 2.8, 6, 7.4, and 9 were 42.8, 63, 80, and 84.5%, respectively. Data fitting process was carried out using five kinetic models (Korsmeyer-Peppas, Higuchi, Hopfenberg, zero-order, and first-order equations) and the preferred kinetic model at each pH was estimated by applying TOPSIS algorithmic technique. The adsorption capacity of the hydrogel in relation to MB was determined while thermodynamic properties of this relationship were quantified (Delta{text{H}}_{text{ad}}^{0}= text{ } -text{99.95 kJ} , {text{mo}}{text{l}}^{-{1}} and Delta{text{S}}_{text{ad}}^{0}= -text{0.237 kJ} , {text{mo}}{text{l}}^{-{1}} {text{K}}^{-{1}}). The results of the present study were in favor of the potential usage of the developed composite hydrogel in drug delivery systems.

Derivation of steady-state first-order rate constant equations for enzyme-substrate complex dissociation, as well as zero-order rate constant equations in relation to background assumptions

Derivation of steady-state first-order rate constant equations for enzyme-substrate complex dissociation, as well as zero-order rate constant equations in relation to background assumptions

Derivation of steady-state first-order rate constant equations for enzyme-substrate complex dissociation, as well as zero-order rate constant equations in relation to background assumptions

The maximum velocity (Vmax) of catalysis and the substrate concentration ([ST]) at half the Vmax, the KM, are regarded as steady-state (SS) parameters even though they are the outcomes of zero-order kinetics (ZOK). The research was aimed at disputing such a claim with the following objectives: To: 1) carry out an overview of issues pertaining to the validity of assumptions; 2) derive the needed steady-state (SS) equations distinct from Michaelian equations that can be fitted to both experimental variables and kinetic parameters; 3) calculate the SS first-order rate constant for the dissociation of enzyme-substrate complex (ES) to free substrate, S and enzyme, E; 4) derive the equation of rate constant as a function of the reciprocal of the duration of each catalytic event in the reaction pathway. The experimental values of the data were generated by Bernfeld and Lineweaver-Burk methods. The calculated SS 1st order-order rate constant was « the zero-order Michaelian value, and the difference is ≈ 97.59 % of the zero-order value; the SS catalytic rate differed from the zero-order catalytic rate by ≈ 76.41 % of the latter value; and it was ≈ 93.87 % with respect to the 2nd order rate constant for the formation of enzyme-substrate complex. The equations of time-dependent rate constants, KM, and dissociation constants were derived. The magnitude of [ST] must be > the concentration ([E0]) of the E for the quasi-steady-state assumption (or approximation) to hold. The SS kinetic parameters are not equivalent to zero-order parameters.

Dissolution and Growth Kinetics and the Rate-Controlling Step in Transformation of Amorphous to Crystalline Phase Using Antisolvent Crystallization

The kinetics of the formation of amorphous disodium guanosine 5′-monophosphate and its transformation to the heptahydrate phase were studied under various operating conditions using in situ Raman and focused beam reflectance measurement (FBRM). Supersaturation, solvent composition, feed concentration, addition rate, and viscosity were shown to affect the rate-determining steps of the transformation. The rate-controlling mechanisms in the overall kinetics have been confirmed. The observation of the slurry viscosity of the suspension of the amorphous phase shows the option to observe the phase transformation. The transformation process was affected by the dissolution, growth, and supersaturation in which the rate-controlling step was divided into two sections, such as the initial and later sections of the transformation. The overall rate constants were determined by combining the constants of the dissolution rate and the growth rates of each section. In situ Raman spectroscopy examination of the concentration of solution and solids can determine the rate-limiting processes during the transformation. The zero-order, first-order, and surface reaction equations as kinetic equations are highlighted and compared for the dissolution of the amorphous solids and the growth of the heptahydrate crystals. The dissolution of the amorphous (metastable form) and the growth of the heptahydrate (stable form) were found to be best fitted to the zero-order kinetic model. In particular, the variation of particle size distribution over time can give the rate-determining steps. These results suggest that the data measured by Raman spectroscopy and FBRM can be successfully coupled into a dissolution and growth model to further grasp and interpret the phase transformation. A dissolution rate-controlling step was dominated by a pattern in which both supersaturation and amorphous dissolution decreased simultaneously, and the growth rate-controlling step was shown in a pattern in which either supersaturation or amorphous dissolution was constant. Furthermore, the growth of heptahydrate crystals at a viscosity of the suspension with the amorphous solids below 70 cp and the dissolution of the amorphous solids above it can be used as the key determinant. Using the method developed and the kinetic constants obtained in this work, it is possible to create an appropriate control strategy to produce the desired form in the final product.

Advantages, disadvantages and methods of applying mathematical models to evaluate water quality in reservoirs: a systematic review

Human activities are affecting reservoir water quality; consequently, methods are necessary to verify those impacts. Mathematical modeling improves the understanding of the anthropic impact on water quality, changes in limnological data, and helps formulate management strategies. However, it is necessary to consider the (dis)advantages as well as the methods used for water-quality assessment in reservoirs. This study conducted a systematic review in four databases: (i) PubMed/Medline; (ii) Scopus; (iii) Web of Science; and (iv) Wiley Online Library. We combined Boolean operators and words aiming to identify papers linked to the scope. Rayyan software allowed the initial screening of the found papers. Peer-reviewed papers and the use of mathematical models to assess reservoir water quality were the inclusion criteria. Exclusion criteria included articles in languages other than English, grey literature, and inaccessible articles. Our research found 169 articles, of which 39 were selected and only 13 were included in the review. Mathematical modeling has many benefits related to real-world problems, but the main disadvantages are process simplification, specific rules of the model, and lack of information or data monitoring. Kinetic equations, regression models, Monte Carlo analysis, finite segment models, modeling tools, zero-order rate equations, partial differential algebraic equations, and predictive analysis are the methods observed in mathematical modeling. This review provides information for unfamiliar managers who intend to use mathematical models to assess the water quality of reservoirs.
 Keywords: limnologic tool, model inventory, water management.

Furan formation in some vegetable oils during heat treatments

Furan formations were monitored in commercially refined sunflower, soybean and olive oils during heat treatments at 170, 180 and 190 °C for 0, 2, 4, 6 and 8 h. The lowest furan concentrations were detected in sunflower oil at all temperatures, while soybean oil generated the highest furan concentration at 190 °C at the end of 8th hour. Furan contents were higher in olive oil at 170 and 180 °C, which might be due to its high diglyceride content. Furan formation linearly increased with time. Zero-order kinetic equations were used to determine kinetic parameters. Temperature was found effective on the furan formation because increases in reaction rate constants were observed by increasing the temperature. Using Arrhenius equation, activation energies of sunflower, soybean and olive oils were calculated as 45.08, 100.24 and 22.41 J/mol, respectively.

Heat and Light Stability of Pumpkin-Based Carotenoids in a Photosensitive Food: A Carotenoid-Coloured Beverage.

This study aimed to evaluate carotenoid degradation kinetics in a beverage coloured with pumpkin juice concentrate during storage at dark and illuminated conditions at four temperatures (10, 20, 35 and 45 °C). Carotenoids were quantified by HPLC-DAD, and kinetic parameters for carotenoid degradation were estimated by one-step nonlinear regression analysis. During dark storage, degradation kinetics was modelled by fractional conversion (all-trans-β-carotene) and zero-order equations (all-trans-antheraxanthin, all-trans-lutein, all-trans-violaxanthin and all-trans-neoxanthin). Storage of samples in a climatic chamber with intense light intensity (1875–3000 lux) accelerated the carotenoid losses. At illuminated conditions, degradation followed a first-order (all-trans-lutein, all-trans-violaxanthin and all-trans-neoxanthin) and fractional conversion model (all-trans-β-carotene and all-trans-antheraxanthin). Carotenoid degradation followed an Arrhenius temperature-dependency, with values lower than 50 kJ/mol. Degradation was shown to be mainly by oxidative reactions. Packaging under minimal oxygen conditions, use of antioxidants (e.g., ascorbic acid), and proper choice of light sources at retail shelves may be considered to optimize the pigment retention in a carotenoid-coloured beverage during storage.

Kinetics of Phenolic Compounds Modification during Maize Flour Fermentation.

This study aimed to investigate the kinetics of phenolic compound modification during the fermentation of maize flour at different times. Maize was spontaneously fermented into sourdough at varying times (24, 48, 72, 96, and 120 h) and, at each point, the pH, titratable acidity (TTA), total soluble solids (TSS), phenolic compounds (flavonoids such as apigenin, kaempferol, luteolin, quercetin, and taxifolin) and phenolic acids (caffeic, gallic, ferulic, p-coumaric, sinapic, and vanillic acids) were investigated. Three kinetic models (zero-, first-, and second-order equations) were used to determine the kinetics of phenolic modification during the fermentation. Results obtained showed that fermentation significantly reduced pH, with a corresponding increase in TTA and TSS. All the investigated flavonoids were significantly reduced after fermentation, while phenolic acids gradually increased during fermentation. Among the kinetic models adopted, first-order (R2 = 0.45–0.96) and zero-order (R2 = 0.20–0.82) equations best described the time-dependent modifications of free and bound flavonoids, respectively. On the other hand, first-order (R2 = 0.46–0.69) and second-order (R2 = 0.005–0.28) equations were best suited to explain the degradation of bound and free phenolic acids, respectively. This study shows that the modification of phenolic compounds during fermentation is compound-specific and that their rates of change may be largely dependent on their forms of existence in the fermented products.

Efficacy of a woodchip-sediment integrated system in nitrate elimination from wastewater with low C/N condition

Currently, effective methods to eliminate nitrate in wastewater with a low C/N ratio are urgently needed. Considering that sediment is the main nitrogen removal carrier in lakes and that woodchip is an excellent carbon source, this study was undertaken under an integrated system of these two substances to explore the process and efficiency of the denitrification involved. Using methods of kinetics and molecular biology, denitrification processes involving a woodchip-sediment system were investigated in an up-flow bioreactor (UFBR). Performance indices, functional genes, and microbial community changes in this integrated system were explored through water quality monitoring, quantitative PCR, and high-throughput sequencing. When the hydraulic residence time reached above 3.82 days, the nitrate elimination efficiency could achieve an effective level of higher than 93.3% even under the different flow rates. It was also noted that the nitrate elimination rate in this integrated system fitted the Michaelis–Menten kinetics, a combination of zero-order equation (R2 > 0.98) and first-order equation (R2 > 0.95). A combination of zero-order kinetic equations of nitrate elimination and total organic carbon (TOC) release exhibited nitrate elimination efficiency under direct influence of TOC release rate on the C/N ratio. Microbiological analysis indicated co-existence of composting bacteria and denitrifiers as well as aerobic degradation and heterotrophic denitrification, with the former process providing effective carbon sources for the latter process. This study provided a deep insight into the denitrification process of a woodchip-sediment integrated system, which might inspire a potential wastewater treatment method for reduced eutrophication in the aquatic environment.

Residue Content of Organophosphorus Pesticides and their Toxic Metabolites in Greenhouse-Grown Tomatoes during Pre-Harvest Interval and Post-Harvest Processing: A Kinetic Study

Background: Organophosphorus pesticides (OPPs) have a wide application throughout the world and exert adverse effects on human health. Moreover, these chemical compounds are responsible for thousands of deaths per year worldwide. Kinetic and mathematical models could be used to optimize the application of pesticides on fruits and vegetables and monitor their residues. Objectives: The present study aimed to model the dissipation of diazinon and chlorpyrifos in different conditions, such as household conditions (e.g., storage at room and refrigerator temperatures, as well as cooking) and field condition for greenhouse tomatoes. Methods: A multi-residue analysis of diazinon, chlorpyrifos, and their oxon derivatives was established by gas chromatography-tandem mass spectrometry. The limit of quantification (LOQ), recovery, precision, linearity, and the limit of detection (LOD) were evaluated to ensure that the method was able to effectively determine the studied pesticides in the tomato samples. The linear and nonlinear kinetic models were presented for chlorpyrifos and diazinon residues in tomato using zero-order, first-order, and second-order equations. Results: Based on the best fitting models for diazinon in the case of laboratory treatment at the refrigerator, room, and boiling temperatures, the half-lives were calculated as 18.79 days, 11.41 days, and 45.39 min, respectively. The half-life of diazinon was lower than that of chlorpyrifos in both field and laboratory treatments. Conclusion: Modeling the removal of the pesticides indicated that the nonlinear first- and second-order models were the best fitted models for the dissipation of both pesticides in field and post-harvest conditions.

Chitosan Epoxidized Natural Rubber Biocomposites for Sorption and Biodegradability Studies.

The slow-release mechanism of copper into soil followed by soil biodegradation was studied using the chitosan (CTS)/epoxidized natural rubber (ENR) biocomposite. The biocomposite was prepared by homogenizing CTS in ENR50 (ENR with about 50% epoxy content) latex in the presence of curing agents and acetic acid. It was found that the adsorption property of the biocomposite was very much influenced by chitosan loading, where 20phrCTS-t-ENR biocomposite can absorb 76.31% of Cu(II) ions. The desorption study indicates that the copper (II) ion can be released at a very slow and control phase as proven by the kinetic study using zero-order, first-order, Higuchi, and Korsmeyer Peppas equations. The slow-release studies comply with the Higuchi square-root equation, indicating that the release process is diffusion-controlled. Results of desorption and biodegradation process suggest that this biocomposite has the potential use of being a slow-release matrix in the field of agriculture.

Preparation and properties of thermosensitive molecularly imprinted polymer based on konjac glucomannan and its controlled recognition and delivery of 5-fluorouracil

Biocompatible thermosensitive molecularly imprinted polymers (MIPs) based on konjac glucomannan was prepared by graft copolymerization of N-isopropyl acrylamide, a thermosensitive monomer, with konjac glucomannan, a natural polysaccharide. The products were characterized by various means. The MIPs possessed switchable thermal regulation on the recognition and delivery of 5-fluorouracil (5-Fu), an anticancer drug. The results of adsorption experiments showed that the MIPs had excellent adsorption capacity at a temperature below the lower critical solution temperature, and the MIPs could specifically recognize and adsorb 5-Fu with good selectivity, repeatability, and stability. The adsorption isotherms of MIPs were fitted by six isothermal models and the dual-site Langmuir- Freundlich model presented the best fit. In addition, the in vitro release properties of 5-Fu from the thermosensitive MIPs were evaluated in phosphate buffer solution and the cumulative release of 5-Fu at 25 °C was higher than that at 38 °C. The release curves were fitted by zero-order, first-order, and Higuchi kinetic equations, respectively, and the results showed that the release of 5-Fu complied with the Fick's law. Compared with non-molecularly imprinted polymers, the MIPs could release 5-Fu continuously for a certain period with a good controlled release effect, indicating that they possess great prospects as drug delivery materials.

Quality deterioration kinetics and shelf-life estimation of fish koya

This study aimed to determine the quality deterioration kinetics of fish Koya and to estimate its shelf-life. Koya is a savory powder and usually added to traditional Indonesian foods such as Soto and noodles. In general, Koya is made from crushed shrimp crackers and fried garlic. In this study, Koya was made from red tilapia and tempeh flour, then packed in metalized plastic. The three formulas in this study were N1 (60% tempeh flour : 40% red tilapia fillets), N2 (50% tempeh flour : 50% red tilapia fillets), and N3 (40% tempeh flour : 60% red tilapia fillets). The Koya then stored at 35°C, 45°C, and 55°C for 28 days. Sensory quality and Thiobarbituric Acid (TBA) values during storage were observed every seven days. The sensory evaluation was conducted using multiple comparisons test. Shelf-life of fish Koya was determined at 30°C (room temperature) using Accelerated Shelf Life Test (ASLT) with the Arrhenius model. The results showed that aroma was the first parameter that decreased compared to other parameters. The zero-order equations were suitable to describe the decreased aroma quality of N1, N2, and N3. The activation energy of decreased quality for N1, N2, and N3 were 29.64 kJ/mol.K, 24.79 kJ/mol.K, and 22.43 kJ/mol.K, respectively. The shelf-life estimation for N1, N2, and N3 at room temperature was 131 days, 109 days, and 108 days, respectively.

Formulation and In vitro Release Behavior of Hydroxypropyl Methylcellulose (HPMC) Matrix Tablet Containing Poorly Soluble Fenofibrate

Fenofibrate, a water insoluble drug was used to prepare matrix tablet with four different viscosity grades of Hydroxypropyl Methylcellulose (HPMC) which were Methocel K4M CR, Methocel K15M CR, Methocel K100M CR and Methocel K100LV CR. The concentration of those excipients was 5, 10, 20, and 40% (w/w), respectively. The content of drug in a fixed quantity of powder in every formulation was ranged between 96.47 to 104.78 %. The dissolution study was done by using USP dissolution apparatus II. The kinetics of release was analyzed by using zero-order, first order, Korsmeyer-Peppas, Higuchi and Hixon-crowell equations to explain the drug release mechanism from the matrix tablets. In-vitro dissolution profile of matrix tablets were dependent upon the HPMC concentration and dissolution was rapid for tablets containing lower polymer proportion i.e. 5,10, and 20% Percentage (w/w) HPMC than those containing 40% (w/w) HPMC. Bangladesh Pharmaceutical Journal 23(1): 10-16, 2020

Modeling and comparison of release profiles: Effect of the dissolution method

During the last decades, the study of the in vitro dissolution of pharmaceuticals has been strongly encouraged by the FDA in order to determine its relationship with the in vivo bioavailability of a drug. In this work immediate and extended release formulations containing diclofenac, a BCS class II drug, were studied using different dissolution methods. The release profiles obtained in USP Apparatus II and USP Apparatus IV were evaluated and compared to determine the effect of the fluid dynamic conditions on the release. The influence of the mixing conditions (i.e. the paddle rotation speed in USP Apparatus II or the inlet flow rate in USP Apparatus IV) on the drug release were evaluated, finding that, for the extended release formulations, they do not affect significantly the release profile. An in vitro device simulating the peristaltic contractions of the stomach during the digestion was used to simulate fluid dynamics closer to the real physiology. The tablets were found to behave in a completely different way if tested in the artificial stomach.Both model-independent and model-dependent approaches were used to compare and fit the dissolution profiles, respectively. Fit factors were used as indicators of similarity of two dissolution profiles; model equations (such as zero-order, first-order, or Korsmeyer-Peppas equations) were used to fit the experimental data. With the identification of the best fitting model by the use of correlation factors and Akaike Information Criterion, the transport phenomena that determine the behavior of each formulation were identified.

Viability kinetics of Lactobacillus casei Shirota strain in a commercial fermented milk drink during refrigerated storage

Background: One of the most important parameters in a commercial fermented milk drink containing probiotics is the viability of the microorganisms. Aims and Objectives: This study described the viability kinetics of Lactobacillus casei Shirota strain in a commercial fermented milk drink during refrigerated storage using nonlinear models. Materials and Methods: Viability of L. casei Shirota strain was monitored during refrigerated storage using standard bacterial plate count method. Several nonlinear mathematical models such as the zero-order, first-order, and second-order kinetic equations were employed in describing the population dynamics. Best-fit models were selected based on prescribed criteria including sum of squares of the error, p-value, and coefficient of determination. Results: The viable counts of L. casei Shirota strain in the fermented milk samples stored under refrigerated conditions decreased from 3.73 × 108 colony forming units per ml (CFU/ml) to 2.70 × 108 CFU/ml when monitored every 3-4 days interval over 10 different monitoring points within the product’s indicated shelf life. The counts significantly differed between the monitoring points that were at least 14 days apart. The lowest viable count was still within the recommended therapeutic dose. The decrease in the bacterial population behaved under a second-order kinetic relationship. Conclusion: The viability of L. casei Shirota strain in a commercial fermented milk product during refrigerated storage is governed in accordance with the second-order kinetic mechanism.

Testing the construct validity of the PICTS proactive and reactive scores against six putative measures of proactive and reactive criminal thinking

ABSTRACTThis study tested the construct validity of the Psychological Inventory of Criminal Thinking Styles (PICTS) Proactive (P) and Reactive (R) scores. The layperson version of the PICTS was administered to 277 (65 male, 212 female) undergraduates and correlated with putative measures of proactive and reactive criminal thinking. The hypothesis that P and the proactive scales would correlate ≥.30 in zero-order correlations and regression equations controlling for R, whereas R and the reactive scales would correlate ≥.30 in zero-order correlations and regression equations controlling for P found support in this study. This corroborates the construct validity of the PICTS P and R scores and indicates that self-report measures of moral disengagement and neutralization, on the one hand, and impulsivity and risk taking, on the other hand, may serve as effective proxies for proactive and reactive criminal thinking, respectively.

Numerical investigation and modeling of reacting gas-solid flows in the presence of clusters

This work presents a volume-filtered formulation for describing chemically reacting flows in the presence of solid catalytic particles. The equations are discretized in a Eulerian–Lagrangian framework and applied to flows of isothermal, heterogeneously reacting chemical species in fully developed three-dimensional risers. The aim of this study is to identify and quantify the influence of particle clusters on heterogenous reactions. The Archimedes number, Ar, is varied from 500 to 12,500, and the Damköhler number, Da, from 0.1 to 10. To assess the multiphase dynamic effects on the chemistry, conversion times from the three-dimensional simulations are compared to a zero-dimensional model that solves for the temporal evolution of the species mass fraction and ignores all spatial variations. The conversion process associated with the three-dimensional simulations is shown to be significantly longer compared to the zero-dimensional solution, with an increasing effect for larger values of Da. The discrepancies can be fully attributed to the presence of clusters, which are accounted for in the zero-order equations by an additional term that contains the covariance between species mass fraction and particle volume fraction fluctuations, which needs to be modeled. To this purpose, contributions to the fluctuating chemical source term are evaluated from the three-dimensional data and discussed, and a presumed-shape probability distribution function (PDF) approach is investigated. This PDF approach models the fluctuating chemical source term by a product of a beta distribution for the species mass fraction and a lognormal distribution for the particle concentration, and yields a mean species solution that agrees very well with the three-dimensional results for the range of Ar and Da considered in this study.

Potassium-Release Characteristics and Their Correlation with Bean (Phaseolus vulgaris) Plant Indices in Some Calcareous Soils

The rate of potassium (K) release from soils can significantly influence K availability to plants. There are few studies about K-release kinetics and K availability in calcareous soils of central Iran. The objective of this study was to study the release rates in 15 different soils from Chaharmahal-Va-Bakhtiari Province through successive extractions with 10 mM citric acid over periods of 2–2016 h and the correlation of K-release characteristics with bean plant indices. The results showed that there was wide variation in the cumulative K release among soils. The cumulative K release ranged from 169 to 1199 mg kg−1. The amounts of K released after 2016 h was not significantly correlated with bean plant indices. Plots of cumulative amounts of K released show a discontinuity in slope at 168 h. Thus, two equations were applied to segments of the total period (2 to 168 and 168 to 2016 h). The amount of K released after 168 h ranged from 62 to 879 mg kg−1. The amount of K released after 168 h was significantly correlated with bean plant indices. In the segment 1 parabolic diffusion, first-order and power function equations and in the second segment parabolic diffusion, first-order, zero-order, and power function equations described K-release kinetics. Release rate constants in the segment 1 were significantly correlated with bean plant indices; however, in the segment 2 release rate constants were not significantly correlated with bean plant indices. The results of our research showed that K-release characteristics after an initial fast reaction play a role in supplying available K and dilute citric acid solution can be used for estimating of K-release kinetics in the studied soils.

Effect of wheat (Triticum aestivum L.) rhizosphere and sewage sludge application on zinc desorption with dilute citric acid

Rhizosphere processes have a major impact on Zn desorption and Zn uptake by plant. However, information about Zn desorption characteristics in the rhizosphere of wheat is limited. Therefore, a greenhouse experiment was performed to determine Zn desorption characteristics in the bulk and rhizosphere soil of wheat (Triticum aestivum L.) of 10 soils amended and un-amended with municipal sewage sludge using rhizoboxes. The kinetics of Zn desorption was determined by successive extraction with 10 mM citric acid in a period of 1–504 h at 25 ± 1°C in the bulk and rhizosphere of un-amended and amended soils. The results showed that the Zn amount extracted after 504 h in the rhizosphere soils was significantly (p < 0.01) higher than the bulk soils. The mean of Zn desorption in the bulk and rhizosphere of un-amended soils were 10.4 ± 0.34 and 11.4 ± 0.43 mg kg−1, respectively, while the mean of Zn desorption in the bulk and the rhizosphere of amended soils were 13.2 ± 0.48 and 14.8 ± 0.67 mg kg−1, respectively. Desorption kinetics of Zn conformed fairly well to the first-order, parabolic diffusion, power function, and zero-order equations. The results of Zn fractionation indicated that exchangeable Zn and Zn associated with organic matter decreased and Zn associated with iron-manganese oxides and residual Zn increased in the rhizosphere soils compared to the bulk soils. Zinc desorption after 504 h and residual Zn in the bulk and rhizosphere of un-amended and amended soils were significantly positively correlated (p < 0.05). Therefore, residual Zn was the main Zn pool that controlled Zn desorption after 504 h in the bulk and rhizosphere soils studied.