Intraparticle Diffusion Equation Research Articles

Improved Carboxylate Density in Functionalized Biochar for Methylene Blue Adsorption

AbstractCarboxylate appended biochar BCKA was synthesized by a two‐step functionalization of leached rice straw biochar using ethyl 2‐bromoacetate/K2CO3/DMF and hydrolysis to furnish the modfied biochar. The modified biochar was characterized using proximate analysis, CHNS, SS CPMAS 13C NMR, FESEM, FTIR, XPS, BET, and zeta potential. Biochar BCKA was optimized for pH and dose, respectively, as 7 and 0.2 g/L for methylene blue (MB) adsorption with a contact time of 6 h at 298 K. MB removal up to 98% from 20 mg/L dye solution, using BCKA as adsorbent pH 7, 298 K. The nonlinear fit to Langmuir, Freundlich, Temkin, SIPS, and D‐R adsorption isotherm showed a good fit with correlation coefficients (R2) 0.970, 0.969, 0.988, 0.984, and 0.983, respectively, and maximum MB adsorption (qm) of 261 mg/g. Thermodynamic parameters for the adsorption of MB using BCKA were 38.72 kJ/mol (∆H°), 225.42 J/mole K (∆S°), and negative ∆G° confirming the spontaneity driven by entropy. Kinetic studies showed good nonlinear fit to pseudo‐second order (R2 0.967), intraparticle diffusion (R2 0.977), and Elovich equation (R2 0.958) with chemisorption‐based interaction between BCKA and MB. Chemisorption, particularly ion exchange on the surface of BCKA with MB, is inferred from the D‐R isotherm and kinetic analysis. Column breakthrough studies showed Thomas model fit with qt 267.09 mg/g, and efficiency >80% was retained for two cycles of MB adsorption.

Graphene Oxide Decorated with Nickel Cobaltite Nanoparticles as an Adsorbent for Cationic Methyl Green Dye: Kinetic, Isotherm, and Thermodynamic Studies

‎تم في هذه الدراسة ، تزيين ‏رقائق أكسيد الجرافين (‏GO‏) بجسيمات ‏كوبلتيت النيكل النانوية ‏NiCo2O4‎‏(‏NC‏) عن طريق الترسيب في ‏الموقع ، وتم استخدام المتراكب ‏المحضر (‏NC: GO‏) كسطح ماز لإزالة ‏صبغة الميثيل الخضراء ( ‏MG‏) من ‏المحاليل المائية. تم التحقق من ‏التغطية الناجحة لأوكسيد الجرافين ‏بجزيئات كوبلتيت النيكل النانوية ‏‏(‏NC‏) باستخدام دراسات ‏FT-IR‏ وحيود ‏الأشعة السينية (‏XRD‏). كانت أحجام ‏الجسيمات البلورية لل ‏NC‏ و ‏ لل ‏GO‏ المزين ب NCهي ‏‎10.53‎‏ نانوميتر ‏‏9.30 نانومتر على التوالي. تم دراسة ‏تأثير العديد من العوامل التجريبية ‏، بما في ذلك زمن التلامس ، وكمية ‏السطح الماز ، ودرجة الحرارة. كان ‏وقت التلامس الأمثل وكمية السطح 120 ‏دقيقة و 3 مجم / لتر على التوالي. ‏تتلائم بيانات الامتزاز بشكل أفضل مع ‏ايزوثيرم ‏Freundlich‏. تم استخدام ‏أربعة نماذج حركية لتتبع عملية ‏الامتزاز: معادلة زائفة من الدرجة ‏الأولى ، ومعادلة زائفة من الدرجة ‏الثانية ، ومعادلة الانتشار داخل ‏الجسيمات ، ومعادلة بويد. أظهرت ‏نمذجة البيانات التجريبية أن حركية ‏الامتزاز كانت ممثلة بشكل جيد ‏بنموذج الرتبة الثانية الزائفة (‏R2 ‎‎= 0.9945‎‏) مع معدل ثابت سرعة يبلغ 3.2 ‏‏× 10 - 3 (جم / مجم. دقيقة). يتم ‏امتصاص صبغة ‏MG‏ تدريجيًا بواسطة ‏الجسيمات النانوية ‏NC‏ من خلال ‏الانتشار داخل الجسيمات ويتم ‏الاحتفاظ بها بعد ذلك في مسام أصغر. ‏أظهرت قيم التحليل الديناميكي ‏الحراري أن عملية امتزاز صبغة ‏MG‏ ‏كانت ماصة للحرارة بطبيعتها ، و ‏تلقائية وعملية الامتزاز فيزيائية. الكلمات المفتاحية: الانتشار داخل الجسيمات ، المسافات البينية، النموذج الزائف من الدرجة الأولى ، معادلة بويد

Graphene Oxide/Polyamidoamine G4 as a High Efficient and Eco-Friendly Adsorbent for Dichromate Ions.

In this study, GO/PAMAM4 was used as a biocompatible nanocomposite adsorbent to adsorb dichromate (DC) ions. In alkaline solutions, DC ions changed to chromate ions which were not adsorbed on the surface of adsorbent. Thus, experiments were carried out in acidic and neutral water solution. Under these conditions, adsorption sites of adsorbent were protonated primary and ternary amine groups of adsorbent shown as -NH3+ and -NHR2+, respectively, that adsorbed DC ions through electrostatic interaction. Adsorption isotherms of DC on GO/PAMAM4 were obtained under various ionic strengths, pHs and temperatures. Isotherms were analyzed by the ARIAN model. The highest observed adsorption capacity of this process was 246.7 mg g-1 at pH=0 and 318 K. Tests at pH=2 showed that this process was endothermic. Adsorption kinetic experiments were carried out under various initial DC concentrations, pHs, temperatures, shaking rates and ionic strengths and were analyzed by the KASRA model and intraparticle diffusion, ISO and NIPPON equations. Pb2+, Cd2+, Cr3+ and tannic acid (TA) were separated by GO/PAMAM4 from DC ions and the GO/PAMAM4 was recycled by using an alkaline solution.

Removal of the bemacid blue E-TL using granular activated carbon from abundant biomass: adsorption isotherm, thermodynamic and kinetic studies

In this work, we were interested in the adsorption of an acid dye, Bemacid Blue E-TL by granular activated carbon based on olive stones. To shed light on the adsorption process, batch experiments were performed to study the effect of operating parameters on the adsorption process such as equilibrium time, GAC dose, pH, initial dye concentration, and temperature. The experimental results showed that the adsorption of the dye Bemacid Blue E-TL by GAC based on olive stones depends on the equilibrium time at 8 hours, the pH is 2 of the solution and the dose is 5 g.L-1. To explain the adsorption equilibrium, the experimental values were examined by Langmuir, Freundlich, and Temkin models. The equilibrium is perfectly described by the Langmuir model whose correlation coefficient is higher than 0.99. The maximum retained quantity of the Bemacid Blue E-TL is 55.6 mg.g-1. Different kinetic models such as pseudo-first order, pseudo-second order, and the intraparticle diffusion equation were used to evaluate the adsorption kinetics. The results of the kinetic modeling showed that the pseudo-second order fitted the data well, with a high coefficient of determination (R2 > 0.99) and intra-particle diffusion is not the only rate-limiting step. The thermodynamic parameter values enthalpy (ΔH°), entropy (ΔS°), and energy change (ΔG°) show that the adsorption processes are endothermic and spontaneous. The various results obtained are promising and encouraging to consider a more comprehensive study with the objective of showing that the adsorbent chosen for this study is effective and could be used as a low-cost adsorbent for acid dye removal.

Adsorptive removal of anthraquinone dye from wastewater using silica-nitrogen reformed eucalyptus bark biochar: Parametric optimization, isotherm and kinetic studies

BackgroundDye sequestration from textile wastewater is required prior to discharge because of environmental concerns and the potential risk posed by colored contaminants. MethodsHerein, a novel composite adsorbent of biochar derived from eucalyptus bark and 3-aminopropyl triethoxysilane (TESPA, as source of silica) and diethylene triamine (DIEN, as source of nitrogen) was synthesized via impregnation method. The prepared adsorbents were characterized by scanning electron microscopy-energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, N2 adsorption-desorption and pH at point of zero charge (pHpzc) analyses. The optimal TESPA: DIEN molar ratio for the silica-nitrogen doped eucalyptus bark biochar (Si-N@EBB) composite to adsorb acid blue 25 (AB25) dye was 2:1. The independent process parameters (contact duration, adsorbent dosage, pH and initial AB25 concentration) influencing the AB25 adsorption by Si-N@EBB2:1 were optimized by Box-Behnken design in response surface methodology at temperature of 26± 2 °C. The obtained experimental data were analyzed by the Langmuir, Freundlich and Temkin isotherms. Kinetic data obtained at various AB25 concentrations were evaluated using pseudo-first-order (PFO), pseudo-second-order (PSO) and intraparticle diffusion equations. Significant FindingsPredicted values of removal efficiency were found to be in agreement with the experimental values obtained (R2 = 0.9823; Adj − R2 = 0.9646). Optimization findings revealed that maximum removal efficiency of 96.03± 2.57 % was achieved at the optimum conditions of 21.01 mg L−1 initial AB25 concentration, 3.91 dye solution pH, 0.913 g L−1 adsorbent dosage and 117.2 min contact duration. The equilibrium adsorption data fitted well to the Langmuir isotherm with a monolayer uptake capacity found to be 197.4 mg g−1. PSO model suited the kinetic data well, indicating the dominance of chemisorption mechanism.

Investigating the impact of adsorbent particle size on column adsorption kinetics through a mathematical model

Experimental data demonstrates that the breakthrough curves of column adsorption exhibit qualitative differences related to the size of the adsorbent particles. Standard models do not account for particle size, consequently, in this paper we develop a new formulation that incorporates the diffusion of the adsorbate into the adsorbent particles. Two kinetic models are considered, Langmuir adsorption and a linear driving force. Approximate analytical solutions are developed for these two models coupled to mass flow and intra-particle diffusion equations. The accuracy of the analytical solutions is verified through comparison with numerical solutions of the full mathematical model. Comparison with experimental data confirms that the new analytical solutions show better agreement than previous models. However, in certain cases, neither form of model predicts the behaviour suggesting a combination of different effects contribute to the breakthrough form.

Novel Inorganic Membranes Based on Magnetite-Containing Silica Porous Glasses for Ultrafiltration: Structure and Sorption Properties

Porous glasses (PGs) obtained from sodium borosilicate (NBS) phase-separated glasses via leaching are promising inorganic membranes. Introducing Fe2O3 into NBS glasses imparts ferrimagnetic properties due to magnetite crystallization. Leaching of such glasses leads to the formation of magnetic PGs with interesting electro-surface characteristics. This work aimed to investigate the process of obtaining magnetite-containing PGs from NBS glasses depending on silica content, using XRPD and Raman spectroscopy, studying the PG membranes' structural characteristics and their sorption properties with respect to methylene blue (MB). Obtained PGs were characterized by a polymodal distribution of mesopores and a small number of micropores with specific surface area values of 32-135 m2/g and an average mesopore diameter of 5-41 nm. The kinetic data were analyzed using pseudo-first-order, pseudo-second-order, and intra-particle diffusion equations. The equilibrium isotherms were fitted with Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models. MB adsorption was found to be a complex process. The glass with the highest specific surface area demonstrated the maximum sorption capacity (10.5 mg/g). The pore size of PGs allowed them to be considered potential novel magnetic membranes for ultrafiltration.

Adsorption study on the removal of ciprofloxacin in aqueous solution by an acidic ion exchange resin with bifunctional group

Removal of fluoroquinolone antibiotic pollutants in the aquatic environment has become a research hotspot. In this work, two skeletal resins and four acidic ion exchange resins have been used as adsorbent materials to evaluate their adsorption properties for fluoroquinolone antibiotic ciprofloxacin (CIP) in aqueous solution. Compared with other materials, the sulfonic-phosphoric acid-based bifunctional resin S9570 has shown the best adsorption performance for CIP. The effect of solution pH on the adsorption of CIP by S9570 has been further explored, and the optimal adsorption capacity has been obtained at pH 4.0. The adsorption kinetics and thermodynamics of S9570 for CIP have been investigated in details. The high fits of the pseudo-second-order and intraparticle diffusion equations indicate that these two models can better describe the adsorption process of S9570 for CIP which has been jointly controlled by chemical adsorption and intraparticle diffusion steps and has been accompanied by weak or intermediate initial adsorption behaviour. The best fit results of Langmuir has indicated that there exists a monolayer adsorption on the surface of the S9570.Thermodynamic parameters suggest that the adsorption is an endothermic, spontaneous process with increased randomness at the solid-liquid interface. Through this evaluation of resin adsorption materials, it has been proved that the adsorbent material has good reusability and antiinterference performance.

Senegalia Catechu activated carbon incorporated Ba-alginate composite beads for the removal of Safranine B: modeling studies

The present investigation depicts the removal of Safranine-Bdye from aqueous solution using senegalia Catechu activated carbon incorporated Ba-alginate composite beads. The alginate beads were synthesized by metal encapsulation technique using BaSO4 as an encapsulating agent. The Safranine-B dye removal efficiency was determinedby the modeling equations like Langmuir and Freundlich. The nature of physical, chemical force of attractionbetween the adsorbate vs. adsorbent and feasibility was determined using pseudo order equations of first andsecond. The progressiveness of the interaction process was predicted by intraparticle diffusion, enthalpy, entropy and Gibbs free energy model equations. Experimentally obtainedoutcomes were implied that the adsorption of Safranine-Bwas feasible for all the parameters used in this study. Furthermore, the predicted diffusion valueswere revealedthat the contact between Safranine-B versus composite beads was well diffused. The surface morphology of virgin and Safranine-B loaded images confirms that the Safranine-B was strappinglybind on outerlayer of the composite. The results of the FTIR spectrum indicatethe Safranine-Bwas intensively attached on thecomposite surface. The TGA result revealsthat the Ba composite bead has predominant temperature bearing nature.

Facile Conversion of Polystyrene Waste into an Efficient Sorbent for Water Purification.

In this work, we convert a plastic waste, i.e., polystyrene (PS), into a sorbent by a simple sulfonation process. The sulfonation time was optimized and the structures of the resulting sulfonated polystyrene (SPS) was characterized by field emission scanning electron microscopy, energy-dispersive X-ray and contact angle tests. The results showed that the sulfonation time of 7 h can introduce abundant sulfonic groups and preserve the self-standing structure. Additionally, the SPS has a three-dimensional porous structure and hydrophilic surface because of the presence of numerous sulfonic groups, which could serve as effective binding sites for immobilizing varying pollutants. Furthermore, as a proof-of-concept, the adsorption performance of the SPS foams was evaluated using three pollutants, namely Pb2+, lysozyme and methylene blue. The adsorption isotherms were fitted by the Langmuir and Freundlich models, while the kinetics of the adsorption processes were analyzed using the pseudo-first-order, pseudo-second-order and intraparticle diffusion equations. It was found that the adsorption isotherms of Pb2+ and lysozyme can be better described by the Langmuir model, leading to maximum equilibrium adsorption uptakes of 10.5 and 15.7 mg g-1 for the adsorption of Pb2+ and lysozyme, respectively. Importantly, the pollutant-saturated SPS is readily regenerated by acid washing, and the recovered sorbents exhibit outstanding cyclic performance. The abundant availability of feedstock, facile preparation and regeneration processes render the SPS foams a promising sorbent for practical applications.

Biosorption kinetics of cerium(III) and cobalt(II) from liquid wastes using individual bacterial species isolated from low-level liquid radioactive wastes.

The existence of toxic heavy metals in the aquatic environment has emphasized a considerable exigency to develop several multifunctional biosorbents for their removal. Herein, three individual bacterial species of Cellulosimicrobium cellulans, Bacillus coagulans, and Microbacterium testaceum were successfully isolated from low-level liquid radioactive wastes. Their loading capacities towards cerium and cobalt metal ions were inclusivity inspected under variable operational parameters of pH, primary pollutant concentration, interaction time, temperature, stirring speed, and biosorbent dosage. By analyzing the influence of solution pH, concentration, temperature, biosorbent mass, and agitation speed on the biosorption kinetics, the biosorption process confirms pseudo-second-order kinetic, intraparticle diffusion, and Elovich equation. Remarkably, the isolated Microbacterium testaceum exhibited high loading capacities reaching 68.1mgg-1, and 49.6mgg-1 towards Ce(III), and Co(II) ions, respectively, at the initial concentration of 2.8mM, pH 4.5, and 25°C. Overall, the isolated bacterial species can potentially be offered up as a promising scavenger for Ce(III) and Co(II) from liquid waste effluents.

Ecofriendly Composite as a Promising Material for Highly-Performance Uranium Recovery from Different Solutions.

The development of new materials based on biopolymers (as renewable resources) is substantial for environmental challenges in the heavy metal and radionuclide ions removal contaminations. Functionalization of chitosan with sulfonic groups was achieved for improving the uranium sorption, not only from slightly acidic leachate, but also for the underground water. The prepared hydrogel based on chitosan was characterized by series of analysis tools for structure elucidation as FTIR spectroscopy, textural properties using nitrogen adsorption method, pHPZC (by pH-drift method), thermogravimetric analysis (TGA), SEM, and SEM-EDX analyses. The sorption was performed toward uranium (VI) ions for adjustment of sorption performances. The optimum sorption was performed at pH 4 (prior to the precipitation pH). The total sorption was achieved within 25 min (relatively fast kinetics) and was fitted by pseudo-first order rate equation (PFORE) and resistance to intraparticle diffusion equation (RIDE). The maximum sorption capacity was around 1.5 mmol U g−1. The sorption isotherms were fitted by Langmuir and Sips equations. Desorption was achieved using 0.3 M HCl solution and the complete desorption was performed in around 15 min of contact. The sorption desorption cycles are relatively stable during 5 cycles with limit decreasing in sorption and desorption properties (around 3 ± 0.2% and 99.8 ± 0.1%, respectively). The sorbent was used for removal of U from acid leachate solution in mining area. The sorbent showed a highly performance for U(VI) removal, which was considered as a tool material for radionuclides removing from aquatic medium.

High-performance photocatalytic degradation of NiO nanoparticles embedded on α-Fe2O3 nanoporous layers under visible light irradiation

Thin layers of pure Fe2O3 and modified by polyvinyl alcohol (PVA) were synthesized by sol gel route. The morphology of Fe2O3 was modified by the creation of pores by evaporating the Polyvinyl alcohol at 550 °C. This modified structure improved the removal rate of methylene blue (MB) dye aqueous solution under visible irradiation in 10%. The effect of sensitization ratio of NiO nanoparticles onto Fe2O3/PVA (porous) showed very good degradation efficiency up to 100%. Characterization of Fe2O3, Fe2O3 modified by PVA (Fe2O3/PVA), Fe2O3/PVA/NiO have been used such as X-ray diffraction (XRD), FT-IR, scanning electron microscopy (SEM), UV–Vis … etc. The kinetic parameters of MB elimination by Fe2O3, Fe2O3/PVA and Fe2O3/PVA/NiO were calculated using linear models such as pseudo-first order (PFO), pseudo-second order (PSO) and Elovich. Four error functions were used namely, correlation coefficients (R2), Root Mean Square Error (RMSE), Mean Square Error (MSE) and Sum Squares Error (SSE), to better fit the kinetic equation. The MB elimination mechanism has been studied based on the intra-particle diffusion equation. The effect of pH on the MB removal rate by the two most active catalysts, Fe2O3/PVA and Fe2O3/PVA/with 1%wt. NiO nanoparticles, as well as the pHPZC point were evaluated.

Nickel ions abatement from aqueous solutions and shipbuilding industry wastewater using ZIF-8-chicken beak hydroxyapatite

In this work, a biocompatible material from chicken beak containing hydroxyapatite (HApB) was modified by the zeolitic imidazolate framework-8 (ZIF-8) compound and used in the Ni2+ abatement from aqueous solutions. Different experimental techniques were used to investigate the properties of adsorbents (HApB and HApB/ZIF-8). The active surface values ​​of ZIF-8, HApB, and HApB/ZIF-8 were determined to be 1063.6, 12.2, and 267.2 m2.g−1, respectively. The synthesized adsorbents had a crystalline structure. Maximum Ni2+ adsorption using HApB (98.82%) and HApB/ZIF-8 (99.12%) was recorded at pH7, Ni2+ quantity of 10 mg.L-1, sorbent mass of 2 and 1 g.L-1, and treatment time of 80 and 40 min, respectively. The kinetic data followed a pseudo-first-order kinetic equation. The intra-particle diffusion equation revealed that penetration through water film and diffusion into particles are effective in Ni absorption. The solid-adsorbent equilibrium using HApB/ZIF-8 followed the Freundlich equation. The maximum decontamination capacity using HApB and HApB/ZIF-8 was determined 24.27 and 63.49 mg.g−1, respectively. Changes in thermodynamic factors showed that the Ni absorption is optimal, exothermic, and spontaneous. The adsorbents were recycled up to 5 cycles and the main adsorbent (HApB/ZIF-8) had a severe efficiency drop in cycles 4 and 5. Investigation of industrial wastewater treatment showed that the desired adsorbents have a nice potential to decontaminate metal ions from aqueous media and wastewater of shipbuilding industries.

Dye removal efficiency of fresh and dry alginate beads incorporating zinc oxide

Alginate beads incorporating zinc oxide (ZnO) nanoparticles were shown as an alternative to treat water contaminated with sedge dye by combining photocatalytic activity with adsorption. Dry and fresh alginate beads were prepared by changing ZnO contents in the range of 0.5, 1, and 2% (w/w) and then characterized for their morphology as well as dye removal. The dye removal efficiency was increased by increasing the active surface area of the alginate beads and ZnO photocatalytic activity. Under ultraviolet irradiation for 24 h, the dye removal efficiency reached 64% in the case of 2% ZnO loading. The use of alginate beads dried at 80 °C before ZnO loading increased the maximum value to 78%. With more than 20% removal during the first 2 h through the adsorption and diffusion, the dye removal of alginate beads incorporating 1 and 2% ZnO was modeled as a function of time according to the Weber-Morris intra-particle diffusion equation. The dye adsorption per mass of the adsorbent having 0 and 0.5% ZnO loading fitted the Elovich equation better.

Single and competitive adsorption of Cu2+ and Pb2+ by tea pulp from aqueous solutions

Background: Removal of heavy metals by bioadsorbents is one of the effective and inexpensive methods for water and wastewater treatment. The aim of this study was to investigate the ability of tea pulp in order to remove Cu+2 and Pb+2 metals in two states of adsorption (single element and two elements) from aqueous solutions. Methods: Experiments were performed on synthetic and real samples at ambient temperature. The effect of solution pH, adsorbent dose, contact time, and initial concentration on single and competitive removal of copper metals and lead was studied. Adsorption kinetics and adsorption isotherms were analyzed by pseudo-second-order kinetic equations, Elovich model and intraparticle diffusion, Freundlich and Langmuir equations, respectively. Results: The maximum adsorption capacity for copper and lead was observed at pH=5-8 and pH=4-8, respectively. Maximum adsorption capacity for copper and lead by tea pulp in single-element solution (single) was 37.17 and 48.54 mg/g and in two-element solution (competitive), was 28.41 and 43.47 mg/g, respectively. The adsorption reaction of heavy metals by tea pulp followed the Longmuir isotherm and pseudo-second-order kinetic models. Conclusion: Tea pulp as an inexpensive bioadsorbents is able to remove about one-third of the copper, and approximately, half of lead from aqueous solutions, so its use in the treatment of aqueous solutions will be beneficial.

Investigation of dye removal ability and reusability of green and sustainable silica and carbon-silica hybrid aerogels prepared from paddy waste ash

In this study, the paddy waste ash (PA) was utilized for producing carbon-silica hybrid (PCS) and silica (PS) aerogels. X-ray fluorescence (XRF) spectrometer analysis revealed a high silica content in PA. Crystalline SiO2-cristobalite structure was observed in the X-ray diffraction (XRD) patterns of PA. As expected, the PCS and PS samples exhibited an amorphous SiO2 phase. The pore enlargement and structural improvement after aerogel synthesis were determined using a N2 adsorption-desorption analysis. The specific surface area of the PCS and PS samples were found to be 519 and 652 m2/g, respectively. From the zeta potential results, the points of zero charge (pHPZC) of the samples were found below “2” except for the PCS sample (pHPZC = 2.08). In the first stage of the Remazol Turquoise GN (RTGN) adsorption experiments, the effect of initial pH (2–8) was examined for PA, PCS, and PS sorbents. The highest dye removal value of the PCS sorbent was 61% at pH = 2, while this value was 17.9% and 21.4% for PS and PA sorbents, respectively. The removal percentage curve exhibited a similar trend to the zeta potential curve of the samples. In the experiments conducted with different amounts of sorbents, the dye removal percentage increased with increasing amounts of sorbents. The experimental results and thermodynamic calculations showed that the RTGN adsorption onto PCS was an endothermic process. Pseudo-first order, pseudo-second order and intra-particle diffusion equations were applied to determine the adsorption kinetics of RTGN onto PCS, and it was found that the experimental data was well-fitted to the pseudo-second order kinetic model. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) adsorption isotherm models were used to define the adsorption mechanism of RTGN onto PCS. The Freundlich and Langmuir isotherm models were in agreement with our experimental data and it was concluded that RTGN adsorption on PCS surface occurred both as single layer and multi-layer, as well as took place on heterogeneous and homogeneous surfaces. Characterization analyses were conducted for the PCS sorbent after use to understand the structural changes after dye removal. The regeneration and reusability of the PCS sorbent were investigated and it was found that it preserved its initial removal ability by about 95% after four cycles. The dye removal percentage of PCS decreased by 28% after five cycles.

Calcium alginate‐regenerated spent bleaching earth composite beads for efficient removal of methylene blue

AbstractThis study aims to find an alternative method to the landfill of spent bleaching earth (SBE), which is a solid waste generated by the refining of edible oil that causes enormous ecological and environmental problems. This solid waste is clay loaded with impurities, colourants, and a large amount of oil entrained during the various stages of refining. In this study, the SBE was initially regenerated (RSBE) by thermal processing in a muffle furnace (temperature: 400°C, time: 1 h) followed by washing with an HCl solution. Then, the regenerated materials were encapsulated with calcium alginate (Alg) to form adsorbent composite beads (Alg‐RSBE). Different Alg/RSBE ratios were applied during materials elaboration, yielding beads denoted Alg‐RSBE 1/1 (1/1, w/w), Alg‐RSBE 1/2 (1/2, w/w), and Alg‐RSBE 1/3 (1/3, w/w), respectively. The Alg–RSBE composite beads were characterized by several methods (FTIR, SEM, EDX, TGA, pHPZC) and used as adsorbents of methylene blue (MB) in a fixed‐bed adsorption system. The adsorption of MB was studied at different experimental conditions such as contact time and initial MB concentration. The results showed that the kinetics of MB adsorption fitted to pseudo‐second‐order kinetics and the adsorption isotherm fitted to Langmuir isotherm. Among the three types of Alg‐RSBE composite beads, Alg‐RSBE 1/1 presents the highest MB adsorption capacity at 833.33 mg/g. Intraparticle and film diffusion equations were used to evaluate the kinetic data. Finally, the regeneration study showed that MB dye was successfully desorbed from Alg‐RSBE 1/1 with removal percentages from 93.32% to 88.15% after six cycles.

Loading and sustained release of sodium alginate membranes on pyridirubicin chloride

To develop diversified drug carriers for local treatment of cancer, three types of alginate membranes were fabricated by spin-coating, freeze drying and electrospinning. The uniaxial tensile test is shown that spin-coated membranes possess the maximum tensile strength. All the three types of membranes present excellent adsorption performance toward pyridirubicin chloride (THP) and the electrospinning membranes exhibit the maximum adsorption mass of 144.13 mg g−1. The pseudo-first order, pseudo-second order, and intra-particle diffusion equation were used to evaluate the kinetic data and the drug adsorption process followed the pseudo-first-order model well. The drug releasing mechanism was studied by using different release medium, and it shows that the release process was undertaken by ions exchange reaction. The result shows that the three types of membranes are promising materials for the local treatment of cancer such as local cancers of the pancreas and trachea.

COMPREHENSIVE UTILIZATION OF PHOSPHOGYPSUM: ADSORPTION OF METHYLENE BLUE AND ITS APPLICATION IN BRICKS

In this work, comprehensive utilization of phosphogypsum was developed. Methylene blue (MB) in aqueous solution was adsorbed by waste phosphogypsum (PG), and then the MB-adsorbed PG was used to the fabrication of PG bricks. The adsorption mechanism and the strength of PG bricks also have been studied. The dye maximum capacity of PG monolayer adsorption was found to be 0.2[Formula: see text]mg/g. The kinetic behavior is more accordant with the intra-particle diffusion equation. The MB-adsorbed PG could be effectively used as a raw material for building material. The mechanical properties of PG bricks were little different from the one of the water-washed PG bricks. The 2h-flexural and compressing strengths were about 2.8[Formula: see text]MPa and 6[Formula: see text]MPa, the dry-flexural and compressing strengths were about 5[Formula: see text]MPa and 20[Formula: see text]MPa.