Higher Adsorption Percentage Research Articles

Agro-Waste Derived Biomass Impregnated with TiO2 as a Potential Adsorbent for Removal of As(III) from Water

A novel type of adsorbent, TiO2 impregnated pomegranate peels (PP@TiO2) was successfully synthesized and its efficacy was investigated based on the removal of As(III) from water. The adsorbent was characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrometer (EDS), X-ray Diffraction (XRD) analysis, and Fourier Transform Infrared (FTIR) Spectroscopy, to evaluate its morphology, elemental analysis, crystallinity, and functional groups, respectively. Batch experiments were conducted on PP@TiO2 for As(III) adsorption to assess the adsorption isotherm, effect of pH, and adsorption kinetics. Characterization data suggested that TiO2 was successfully impregnated on the biomass substrate. The equilibrium data better fitted to the Langmuir isotherm model having a maximum adsorption capacity of 76.92 mg/g and better distribution coefficients (KD) in the order of ~103 mL/g. The highest percentage of adsorption was found at neutral pH. The adsorption kinetics followed the pseudo-2nd-order model. X-ray Photoelectron Spectroscopy (XPS) of the adsorption product exhibited that arsenic was present as As(III) and partially oxidized to As(V). PP@TiO2 can work effectively in the presence of coexisting anions and could be regenerated and reused. Overall, these findings suggested that the as-prepared PP@TiO2 could provide a better and efficient alternative for the synergistic removal of As(III) from water.

A Comparative Study for Removal of Perfluorooctanoic Acid Using Three Kinds of N-polymer Functionalized Calotropis Gigantea Fiber

ABSTRACT Using NaClO2 pretreated Calotropis gigantea fiber (CGF) as the bio-template, three N-polymer functionalized fibers were fabricated by in-situ growth of polydopamine (PDA), polyaniline (PAN) and poly(m-phenylenediamine) (PmPD) along the fiber. The resulting adsorbents were applied to remove perfluorooctanoic acid (PFOA) from water. The adsorption process reached equilibrium within 3 h, and the maximum adsorption capacity was 207.3–232.8 mg/g. Electrostatic attraction, hydrogen bond and hydrophobic interaction participated in the adsorption process. Three adsorbents could be well regenerated, and the recovered adsorbents maintained higher adsorption percentage (≥80%) after five adsorption-desorption cycles. Among three adsorbents, PAN-CGF displayed remarkable adsorption performance on perfluorochemicals removal.

Adsorption of selected azo dyes from an aqueous solution by activated carbon derived from Monotheca buxifolia waste seeds

In this study, activated carbon derived from Monotheca buxifolia waste seeds was used for the adsorptive removal of a number of selected azo dyes such as Eriochrome Black T (EBT), Remazol brilliant blue (RBB), Remazol yellow (RY) and Remazol brilliant orange (RBO) from an aqueous solution by changing the initial dye concentration, adsorbent dosage, solution pH, contact time and temperature. A Fourier transform infrared spectroscopic analysis of the activated carbon showed the existence of hydroxyls, methyl, methylene, carbonyls, alkane and alkenes groups while the scanning electron microscopic image displayed the gradual formation of cavities and open pores on the surface. The results showed that as the amount of the adsorbent and the shaking time were increased, the removal percentage of the dye increased accordingly. Higher adsorption percentages were observed at a lower dye concentration and temperature in an acidic media at a pH range (1–5). The investigated data were evaluated with the Langmuir and Freundlich adsorption models. The maximum adsorption capacities obtained from the Langmuir model were 112.36, 96.34, 97.65 and 90.91 mg/g for EBT, RBB, RY and RBO, respectively. The results indicated that the electrostatic interaction was the main cause of the adsorption of these anionic azo dyes on the surface of the activated carbon.

Mercury fractionation in tropical soils: A critical point of view

Problems related to specificity and re-precipitation of metals in sequential chemical extractions can impair their routine use. In order to test the efficiency of a sequential chemical procedure, model compounds composed by soil components commonly found in tropical soils such as goethite, Al-goethite, ferrihydrite, hematite, bauxite, and humic acid were incubated with either Hg(NO3)2 or HgSO4 and submitted to chemical extraction. The procedure aims to assess: (i) water soluble Hg; (ii) bioaccessible Hg at pH near human stomach; (iii) Hg associated with organic matter; (iv) reduced Hg; (v) Hg associated with Fe, Al, and Mn oxides; and, (vi) residual Hg. This procedure was also tested via single and sequential extractions using the surface and subsurface samples of two tropical soils, i.e., a Rhodic Acrudox and a Typic Hapludox, with and without lime application. Soil samples were submitted to an adsorption experiment with HgCl2 and a high adsorption percentage was observed. The majority of Hg at both single and sequential procedure was extracted by an acetic acid solution (pH = 2). Liming, soil depth, and soil type were not determinative on Hg extractability. The sequential extraction applied showed a lack specificity of Hg fractions, confirmed by the model components.

Ultrasonic-enhanced synthesis of rubber-based hydrogel for waste water treatment: Kinetic, isotherm and reusability studies

Hydrogel is used as an adsorbent for the removal of dyes and heavy metals in waste water. In this work, different methods of synthesising novel hydrogels from liquid natural rubber (LNR) were investigated. The two different methods were ultrasonic-assisted polymerisation and heating under reflux. Through graft modification, LNR had initially combined with maleic anhydride (MaH) using benzoyl peroxide (BPO) as a radical initiator. After grafting, acrylic acid (AA) was crosslinked onto LNR-g-MaH using N,N-methylenebisacrylamide (MBA) and potassium persulfate (KPS) as a crosslinker and initiator, respectively. The best method between the two different techniques was identified via a five-level-two-factor response surface methodology (RSM). Higher adsorption percentage (93.34%) was observed in the ultrasonic technique. Meanwhile, the effects of adsorbent mass, dye concentration, pH solution and ionic strength were also investigated and results showed that different conditions were found to give different MG dye adsorption rates. The adsorption of MG dyes on hydrogel is dependent on pH and ionic strength solution. This action indicates an ion exchange mechanism. From an isotherm study, it was found that the Freundlich isotherm best fitted the adsorption of MG dyes. Furthermore, the adsorption kinetic data followed the pseudo-second order kinetic model and the reusability of hydrogel was also investigated.

RSM-CCD design of malachite green adsorption onto activated carbon with multimodal pore size distribution prepared from Amygdalus scoparia: Kinetic and isotherm studies

In the present work, the activated carbon (AC) adsorbent with multimodal pore size distribution prepared from Amygdalus scoparia as low-cost and locally available source was applied for efficient adsorption of malachite green (MG) from aqueous media. The surface properties of the adsorbent were identified by various techniques such as FT-IR, BET and SEM analyses. The dependency of MG adsorption efficiency on the variables such as pH, initial dye concentration, adsorbent dosage and contact time was studied by central composite design (CCD) coupled with response surface methodology (RSM). A good agreement between experimental and predicted data was achieved that proved the efficiency of this model for prediction of real optimum point. Among the well-known previously isotherm models, the experimental equilibrium data were efficiently fitted by the Freundlich model, while maximum adsorption capacity of MG at 0.01 g of the adsorbent was 144.30 mg g−1. The kinetic data were efficiently interpreted by the combination of pseudo-second-order and intra-particle diffusion models. The advantage of the green adsorbent was that a small amount of the adsorbent (0.027 g) is applicable for high adsorption percentage of MG (>99.5%) within a reasonable time (75 min).

Study on adsorption of Congo red onto chemically modified egg shell membrane

Consumption of eggs leads to generation of huge amount of waste in the form of egg shell, which consists of calcined shell and fibrous membrane. In this study, egg shell membrane (ESM) were chemically modified and used to adsorb congo red from its synthetic aqueous solution. Fourier Transform Infra-red (FTIR) spectra confirmed the presence of hydroxyl, carbonyl and methylene groups in egg shell membrane. Scanning Electron Micrographs (SEM) were also performed to characterize the modified egg shell membrane. Concentration of congo red was measured by using UV spectrophotometer. Effects of various parameters such as initial pH, ESM dosage, contact time and initial congo red concentration were investigated. Highest percentage of adsorption (98%) was obtained at pH 4.5 at a solid to liquid ratio of 1 g–100 ml of congo red solution of concentration of 100 mg/l. Pseudo-second order kinetic model was the best fitted model for this study. The reaction rate constant was found to be 58.04 × 10−3 g mg−1·min−1. The adsorption mechanism was supposed to happen via film diffusion as well as via intraparticle diffusion. Langmuir isotherm gave a better fit for the adsorption compared to the Freundlich isotherm. The maximum monolayer adsorption capacity was determined to be 117.65 mg/g. Thermodynamic parameters (ΔG, ΔH and ΔS) were also studied in this work. The change in enthalpy and change in entropy was found to be 29.217 kJ/mol and 0.124 kJ/mol·K, respectively. The values of ΔG were found to become more negative with increasing temperature.

Candida utilis ATCC 9950 Cell Walls and β(1,3)/(1,6)-Glucan Preparations Produced Using Agro-Waste as a Mycotoxins Trap.

Mycotoxins are harmful contaminants of food and feed worldwide. Feed additives with the abilities to trap mycotoxins are considered substances which regulate toxin transfer from feed to tissue, reducing its absorption in animal digestive tract. Market analysis emphasizes growing interest of feed producers in mycotoxins binders obtained from yeast biomass. The aim of the study was to prescreen cell walls (CW) and β(1,3)/(1,6)-glucan (β-G) preparations isolated from Candida utilis ATCC 9950 cultivated on waste potato juice water with glycerol as adsorbents for aflatoxin B1 (AFB1), zearalenone (ZEN), ochratoxin A (OTA), deoxynivalenol (DON), nivalenol (NIV), T-2 toxin (T-2) and fumonisin B1 (FB1). The adsorption was studied in single concentration tests at pH 3.0 and 6.0 in the presence of 1% of the adsorbent and 500 ng/mL of individual toxin. Evaluated CW and β-G preparations had the potential to bind ZEN, OTA and AFB1 rather than DON, NIV, T-2 toxin and FB1. The highest percentage of adsorption (about 83%), adsorption capacity (approx. 41 µg/ g preparation) and distribution coefficient (458.7mL/g) was found for zearalenone when CW preparation was used under acidic conditions. Higher protein content in CW and smaller particles sizes of the formulation could influence more efficient binding of ZEN, OTA, DON and T-2 toxin at appropriate pH compared to purified β-G. Obtained results show the possibility to transform the waste potato juice water into valuable Candida utilis ATCC 9950 preparation with mycotoxins adsorption properties. Further research is important to improve the binding capacity of studied preparations by increasing the active surface of adsorption.

Removal of Three Fluoroquinolone Antibiotics by NaClO2-modified Biosorbent from Fruit Fiber of C. Procera

ABSTRACT Here, Calotropis gigantea fiber (CGF) was first treated using NaClO2 to chemically modify the fiber surface to improve its hydrophilicity. Subsequently, the resulting NaClO2-CGF was used as the biosorbent to remove three fluoroquinolone antibiotics including enrofloxacin (Enr), ciprofloxacin (Cip), and norfloxacin (Nor). The results demonstrate that NaClO2-CGF shows optimum adsorption properties at pH = 6, with the maximum adsorption capacity of 50–70 mg/g. Further, NaClO2-CGF can achieve its adsorption equilibrium within 30 min, an indication of its fast adsorption kinetics. After five adsorption-desorption cycles, a higher adsorption percentage is still observed, suggesting its good regeneration for use in successive cycles.

Highly efficient adsorption of fluoroquinolone antibiotics using chitosan derived granular hydrogel with 3D structure

Here, a granular hydrogel prepared from chitosan as the grafted backbone and acrylic acid as the polymerizable monomer was used as the adsorbent to remove two typical fluoroquinolone antibiotics, i.e. ciprofloxacin and enrofloxacin. The parameters affecting the adsorption capacity were investigated via a series of adsorption experiments, including pH (2.0–9.0), contact time (1–180 min), initial concentration (10–600 mg/L), and ion strength (1 mM and 10 mM NaCl/CaCl2). The results showed that the granular hydrogel possessed porous 3D structure and, the ionizable characterization of COO− groups made the adsorbent be pH-sensitive and the maximum adsorption occurred at pH = 3.0. Moreover, the presence of abundant COO− groups within 3D structured network provided the adsorbent with higher adsorption capacity of 267.7 mg/g for ciprofloxacin and 387.7 mg/g for enrofloxacin. When the initial concentrations were 10, 50 and 250 mg/L, the equilibrium time was determined to be 30, 60 and 120 min, respectively. After five consecutive adsorption-desorption cycles, a higher adsorption percentage (>85%) was still obtained, demonstrating that the developed adsorbent could be easily regenerated and reused for several times.

Comparative study of uranium and thorium metal ion adsorption by gum ghatti grafted poly(acrylamide) copolymer composites.

Uranium and thorium ions were selectively removed from aqueous solution using synthesized gum ghatti grafted poly(acrylamide) gum-g-poly(AAm) composite. A gamma radiation induced free radical copolymerization technique was used to synthesize the copolymer composite of gum-g-poly(AAm). Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were used to characterize the graft copolymer gum-g-poly(AAm). The adsorption of uranium ions and thorium ions using the gum-g-poly(AAm) copolymer composites has been investigated in batch mode. The adsorptive characteristics were investigated by varying the pH, concentration and time for both ions. The adsorption method depends on the pH of each metal ion, and the highest adsorption percentage was achieved at pH 6.0. The adsorption statistics were justified by isotherm, kinetic and thermodynamic models. The Langmuir adsorption model was revealed to be the best fitted monolayer arrangement, with a maximum adsorption capacity of 367.65 mg g−1 for the uranium ions and 125.95 mg g−1 for the thorium ions. The adsorption of metal ions occurred by the ion exchange process, which was specified through the rate controlling step with a best-fitted pseudo-second order kinetic rate model. Thermodynamic analysis shows that the ΔH and ΔS values for the uranium ions and thorium ions were positive. The negative ΔG values decreased with an increase in temperature, suggesting that the metal ion adsorption process was endothermic and spontaneous in behaviour.

A pilot level approach to remove anionic species from industrial effluents using a novel carbonate-steam pyrolysed activated charcoal system

In our laboratory, we synthesized a novel surface tailored activated charcoal in removing nitrite species from fertilizer industrial effluents. A customized high temperature carbonate-steam activation technique was adopted to develop the sodium carbonate impregnated activated charcoal (SCIAC). The surface properties of the material were determined using SEM, TG and X-RD techniques. Batch adsorption experiments were performed for optimizing various conditions such as solution pH, contact time, temperature and adsorbent dose for maximizing the nitrite adsorption onto SCIAC. Considerably, a very high nitrite adsorption percentage of 83.8 was obtained for an initial nitrite concentration of 5.0 mg/L at pH 3.0. Among the various equilibrium and kinetic models, Freundlich and pseudo-second-order expressions, respectively, were well enough to explain the adsorption processes. In general, it may conclude that the change in surface characteristics of the adsorbent material after the pyrolysis process is highly favorable for effective removal of nitrite ions from aqueous systems. Adsorption capacity of SCIAC was 27.03 mg/g and studies revealed that the material was feasible in removing nitrite from industrial effluents.

Greener Method for the Removal of Toxic Metal Ions from the Wastewater by Application of Agricultural Waste as an Adsorbent

The presence of inorganic pollutants such as metal ions (Ni2+, Pb2+, Cr6+) in water, probably by long-term geochemical changes and from the effluents of various industries, causes diseases and disorders (e.g., cancer, neurodegenerative diseases, muscular dystrophy, hepatitis, and multiple sclerosis). Conventional methods for their removal are limited by technical and economic barriers. In biosorption, low-cost and efficient biomaterials are used for this purpose. In this study, Brassica Campestris stems from the agriculture waste and has been used for the removal of Ni2+, Cr6+ and Pb2+ ions from an aqueous solution containing all the ions. Effect of different parameters, e.g., pH, contact time, metal ion initial concentration, adsorbent dose, agitation rate and temperature were analyzed and optimized. The adsorbent worked well for removal of the Pb2+ and Cr6+ as compared to Ni2+. The atomic absorption spectrophotometer (AAS) and FTIR investigation of adsorbent before and after shows a clear difference in the adsorbent capability. The highest adsorption percentage was found at 98%, 91%, and 49% respectively, under the optimized parameters. Furthermore, the Langmuir isotherm was found better in fitting to the experimental data than that of the Freundlich isotherm.

Synthesis of aluminum pyrophosphate for efficient sorption of U(VI)

In this study, aluminum pyrophosphate (Al4(P2O7)3) was synthesized successfully and applied to adsorb radioactive uranyl ions from aqueous solutions. The material displayed an excellent sorption capacity of removing U(VI) (12.83mg·g−1), achieved a relatively high adsorption percentage (71%) within an hour. In order to reveal its adsorption mechanism, the materials before and after adsorption of U(VI) were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transformed infrared spectroscopy (FT-IR). The factors affecting the adsorption performance, such as shaking time, pH value, ionic strength, temperature and so on, were investigated. Based on the above research, the results demonstrated that the chemical adsorption plays a leading role in the process of adsorption, the adsorption process is more suitable to monolayer adsorption, and the adsorption thermodynamics results suggested the adsorption process was spontaneous (ΔG°<0) and exothermic (ΔH°>0). Moreover, the ionic strength and pH have important influence on the sorption of U(VI). Those researches may be valuable for the application of aluminum pyrophosphate in the area of radioactive water pollution governance.

Competitive adsorption, selectivity and separation of valuable hydroxytyrosol and toxic phenol from olive mill wastewater

Competitive adsorption and selectivity of toxic phenol and hydroxytyrosol were studied on the macroreticular aromatic polymer (FPX66) and the macroporous polystyrene cross linked with divinylbenzene (MN202). The adsorption equilibrium of phenol and hydroxytyrosol as well as other phenolic compounds in olive mill wastewater (OMW) was investigated taking into account the different affinities of these compounds towards the two above mentioned resins. The experimental results showed that the adsorption equilibrium of phenol on FPX66 can be well interpreted by the BET model, indicating a multilayer adsorption, whereas, the adsorption of hydroxytyrosol on MN202 at equilibrium is well fitted by the Sips model. At low FPX66 concentration, phenol exhibited much higher adsorption percentage than hydroxytyrosol, indicating a stronger interaction with the resin. The adsorption selectivity ratio of phenol/hydroxytyrosol was of about 3.215 at 5gL−1 of FPX66. Thanks to the large affinity of hydroxytyrosol for the MN202 resin, its adsorption and recovery were higher than 90% on this resin. Thus, under suitable operating conditions, phenol was selectively separated on FPX66, while hydroxytyrosol was largely recovered from the OMW residual solution by adsorption on MN202.

Preparation of Fe3O4-chitosan hybrid nano-particles used for humic acid adsorption

The adsorbent of Fe3O4-chitosan hybrid nano-particles have been prepared. In this process, these materials were initially synthesized by chemical co-precipitation and then cross-linked with chitosan to coat on the surface of Fe3O4 nano-particles. The characterization of the synthesized Fe3O4-chitosan hybrid nano-particles was performed using FTIR, XRD, TEM, EDX, BET and TGA. Finally, the Fe3O4-chitosan hybrid nano-particles were used for the adsorption of humic acid (HA) from aqueous solutions using batch adsorption technique. The influences of contact time, pH, adsorbent dosages, initial concentration of HA and temperatures on the adsorption process were studied. The adsorption isotherms were better fitted by Langmuir isotherm with the adsorption capacity was found to be 44.84mg/g. The results of the kinetic study showed that the adsorption of HA onto Fe3O4-chitosan hybrid nano-particles could be described by the pseudo second order kinetic model with a rate constant in the range of 0.032–0.104gmg−1min−1, respectively. Thermodynamic parameters data indicated that the HA adsorption process was non spontaneous and endothermic under the experimental conditions, with the values of Gibbs free energy (ΔGo) were in the range of 2.92–4.65kJ/mol; as well as the values of enthalpy (ΔHo), entropy (ΔSo) and the activation energy (Ea) were found to be 21.80kJ/mol, 57.55J/mol and 19.27kJ/mol, respectively. The computational chemistry study showed that the interaction between adsorbent and HA was occurred through the interaction between amine groups of chitosan and phenol groups of HA. The adsorption of HA from real sample using the prepared adsorbents showed that the Fe3O4-chitosan hybrid nano-particles has higher adsorption percentages than both Fe3O4 nano-particles and pure chitosan.

ADSORPSI β-KAROTEN YANG TERKANDUNG DALAM MINYAK KELAPA SAWIT (CRUDE PALM OIL) MENGGUNAKAN KARBON AKTIF

&#x0D; Crude palm oil (CPO) is the richest natural source of carotenoids which gives the reddish-orange color in crude palm oil. The reddish color in unprocessed palm oil is disliked by consumer. This research is aimed to adsorb the β–carotene from the CPO using activated carbon, then the kinetics, isotherm models and thermodynamics data of the adsorption process were obtained. The main materials used in this research were CPO and activated carbon. The observed parameters were final concentration and the amounts of adsorbed β–carotene in activated carbon. The adsorption process was conducted by mixing the adsorbent with CPO with the variation of adsorbent: CPO (w/w) ratio = 1 : 3; 1 : 4; 1 : 5 and 1 : 6 with mixing speed 120 rpm and the temperature of 40, 50 and 60 oC. The sample of CPO and activated carbon was analyzed at every 2 minutes until the equilibrium was achieved. The final concentration of the unadsorbed β–carotene was analyzed using UV-Vis spectrophotometer. The results showed that the more CPO used in the process, the lower the adsorption percentage. The higher the adsorption temperature, the higher adsorption percentage. Moreover, the maximum adsorption percentage was 95.108% obtained at ratio 1 : 3 and T = 60 oC. The adsorption isotherm model which fit with the β–carotene adsorption at T = 60 oC was Langmuir model with the correlation coefficient of 0.959. The adsorption kinetics model which fit with the β–carotene adsorption was the second order kinetics model with the correlation coefficient of 0.998. The value of free energy Gibbs (ΔG) = -24,482.484 ; -24,708.059 and -24,933.634 J/mol for each temperature respectively, value of entropy changes (ΔS) = 22.557 J/mol K, and value of enthalpy changes (ΔH) = -17,421.987 J/mol.&#x0D;

Studies on Copper Ion Adsorption Using Pectin/Functionalized-Silica Coated Cellulose

The pectin/functionalized silica coated filter paper (FILPSL2) was used for copper ion adsorption. Silica sol (1), prepared by mixing ethanol, water, TEOS and hydrochloric acid, was slowly added into pectin solution. A piece of filter paper (2 cm x 2 cm) was immersed in the silica-pectin solution for 1 hr. The coated filter paper was dried at room temperature and then oven-dried at 50 °C for 6 hrs to obtain FILPS. The silica sol (2) was subsequently prepared by mixing ethanol, water, N-[3-(Trimethoxysilyl) propyl] ethylenediamine (L2) and hydrochloric acid. The FILPS was immersed in silica sol (2) and the coated paper was oven-dried at 50 °C for 6 hrs to obtain FILPSL2. The SEM micrograph of uncoated Filter paper (FIL) and FILPSL2 showsa characteristic woven pattern. For copper ion adsorption, FILPSL2 was put into 0.1 M of CuCl2solution (pH 2, 25 °C). The color of the paper changes from off-white to intense blue within 5 min due to the complex between amino group of functionalized silica and Cu2+ as evidenced from IR spectroscopy.The equilibrium adsorption percentage and adsorption capacity were 27.10 and 5.5 x 10-3 respectively. The concentrations of copper ion solutions were varied to 10-2and 10-3M at this pH. The lower concentration of copper ion results in the higher adsorption percentage. While the lower concentration of copper ion results in the lower adsorption capacity. The adsorption was also experimented at pH 3.The similar trend was obtained. The optimum pH for adsorption for all concentrations was 2. The effect of interferences on the copper ion adsorption depends on the pH. At pH 2, Ni2+ has a stronger effect. While Cd2+ has a stronger effect at pH 3. The desorption was performed using 0.2 M CH3COOH solution. The complete desorption occurred within 30 min.

Assessment of cadmium and lead adsorption in organic and conventional coffee.

Many metals are toxic in human organism, as is the case of cadmium and lead. Therefore, the metal levels in food need to be controlled. In coffee, metals may present risks when they are extracted from the powder to be consumed as beverage. A flow injection analysis (FIA) system is proposed, with atomic absorption detection, to metal adsorption studies in coffee powder. Kinetic study, best isotherms and time, and mass influences were determined. They allowed analyzing the high lead and cadmium adsorption percentage in organic and conventional ground coffee. Metal adsorption occurs in multilayers, following Freundlich's model, and the kinetic model obeyed is the pseudo-second order. The cadmium adsorption suffered higher temperature influence, while the lead retention suffered higher mass influence. This study indicates that the majority of these toxic agents will be retained in the powder and will not be consumed by man, avoiding possible deleterious effects.

Development of an in vitro method for the prediction of mycotoxin binding on yeast-based products: case of aflatoxin B1, zearalenone and ochratoxin A

To date, no official method is available to accurately define the binding capacity of binders. The goal is to define general in vitro parameters (equilibrium time, pH, mycotoxin/binder ratio) for the determination of binding efficacy, which can be used to calculate the relevant equilibrium adsorption constants. For this purpose, aflatoxin B1 (AFB1), zearalenone (ZEA) or ochratoxin A (OTA) were incubated with one yeast cell wall in pH 3, pH 5 or pH 7 buffers. The percentage of adsorption was recorded by quantitation of remaining mycotoxins in the supernatant and amount of mycotoxin adsorbed on the residue. The incubation of yeast cell wall in the presence of mycotoxins solved in buffer, lead to unexpected high adsorption percentage when the analysis was based only on remaining mycotoxins in the supernatant. The decrease of mycotoxins in the supernatant was not correlated to the amount of mycotoxins found in the residue. For this reason we modified the conditions of incubation. Yeast cell wall (5 mg) was pre-incubated in buffer (990 μl) at 37 °C during 5 min and then 10 μl of an alcoholic solution of mycotoxin (concentration 100 times higher than the final concentration required in the test tube) were added. After incubation, the solution was centrifuged, and the amount of mycotoxins were analysed both in the supernatant and in the residue. A plateau of binding was reached after 15 min of incubation whatever the mycotoxins and the concentrations tested. The adsorption of ZEA was better at pH 5 (75 %), versus 60 % at pH 3 and 7. OTA was only significantly adsorbed at pH 3 (50 %). Depending on the pH, the adsorptions of OTA or ZEA were increased or decreased when they were together, indicative of a cooperative effect.