Pseudo-second Order Equation Research Articles

Adsorptive Removal of Bisphenol A by Polyethylene Meshes Grafted with an Amino Group-Containing Monomer, 2-(Dimethylamino)ethyl Methacrylate

The adsorptive removal of Bisphenol A (BPA) with the PE meshes photografted with 2-(dimethylamino)ethyl methacrylate (DMAEMA) was performed by varying the grafted amount, pH value, BPA concentration, and temperature, and the adsorption performance was correlated by the equilibrium, kinetic, and isotherm models. In addition, the regeneration of DMAEMA-grafted PE (PE-g-PDMAEMA) meshes was discussed from the repetitive adsorption/desorption process. The adsorption capacity had the maximum value at the grafted amount of 2.6 mmol/g and at the initial pH value of 8.0. The increase in the protonation of dimethylamino groups on grafted PDMAEMA chains and the dissociation of phenol groups of BPA present in the outer solution during the adsorption process results in the increase in BPA adsorption. The adsorption process followed the pseudo second-order equation. The BPA adsorption was enhanced by increasing the BPA concentration and the equilibrium data fit to Langmuir equation. The adsorption capacity stayed almost constant with the increase in the temperature, whereas the k2 value increased against the temperature. These results comprehensively emphasized that BPA adsorption occurred through the chemical interaction or ionic bonding of a BPA anion to a terminal protonated dimethylamino group. Desorption of BPA increased by increasing the NaOH concentration and BPA was entirely desorbed at more than 20 mM. The cycle of adsorption at pH 8.0 and desorption in a NaOH solution at 100 mM was repeated five times without loss or structural damage. These results indicate PE-g-PDMAEMA meshes can be used as a regenerative adsorbent for BPA removal from aqueous medium.

CARBON-SILICA COMPOSITE AS ADSORBENT FOR REMOVAL OF CATIONIC DYE (METHYLENE BLUE)

The aim of this research was to synthesize carbon-silica composite (CSC) as an adsorbent for cationic dye removal from wastewater. Molasses, a by-product of the sugar industry, was successfully utilized to prepare CSC by sol-gel method with tetraethoxylsilane (TEOS) as silica source. The physicochemical properties of the composites were studied by N2 adsorption, FTIR and TGA. The highest specific surface areas of CSC was 144 m2/g at a molasses/TEOS ratio of 0.8, with a mesopore volume of 83% and average pore width of 9.71 nm. This optimal CSC was evaluated for methylene blue (MB) adsorption using batch experiments under varying adsorption times and initial MB concentrations. Adsorption equilibrium was reached within 14 h and the pseudo-second order equation provided the adequate fit for the kinetic studies, suggesting that dye adsorption was limited by chemisorption. The equilibrium data were best described by the Sips model with a maximum adsorption capacity of 180.22 mg/g. The CSC derived from molasses is considered a potentially promising adsorbent for cationic dye removal in wastewater.

Sol-gel synthesis, structure and adsorption properties of LiMgxMn(2-x)O4 (0 ≤ x ≤ 0.7) Oxides

Lithium manganese оxides with a spinel structure LiMgxMn(2–x)O4, doped with Mg2+ ions in the range 0 ≤ x ≤ 0.7, were obtained by sol-gel synthesis. Phase composition and morphology of obtained оxides were studied by using X-ray phase analysis and scanning electron microscopy. It is shown, that in the studied range 0 ≤ x ≤ 0.7 Mg-doped lithium manganese оxides saved the structure of the original cubic spinel LiMn2O4, while an increase in parameter a was observed from 8.175 to 8.309 Å and average crystallite size practically unchanged (30–36 nm). Samples of the initial LiMn2O4 and Mg-doped spinels were represented by prismatic particles of submicron (0.1–0.2 µm) and micron (1.0–3.0 µm) sizes, respectively. The effect of the adsorbent dose (0.05–0.3 g/l) and pH (3.0–13.0) of the solution on the adsorption efficiency was studied. The adsorption isotherms of the LiMg0.3Mn1.7O4 samples were described by the Langmuir monomolecular adsorption equation. An increase in the temperature of the model solution from 25 to 45°C was accompanied by an increase in the maximum adsorption of the LiMg0.3Mn1.7O4 samples from 10.50 to 10.98 mmol/g, which indicates the endothermic nature of the adsorption process. The kinetics of adsorption was well described by a pseudo-second order equation, which indicates the occurrence of chemical interaction during the adsorption process.

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

A novel adsorbent for the removal of chromium form aqueous solution by Acacia Fumosa seed shell activated carbon

In this experimental study, the activated carbon was synthesized by acid impregnation and digestion methods using Acacia Fumosa seed shell. The chromium removal was examined by altering the process conditions like carbon dose, chromium concentration, pH, and temperature and interaction time. The viability of the sorption process was examined using Freundlich and Langmuir equations. Evaluating the isotherm equations, the Langmuir equation shows more concordance compared with Freundlich equation. The feasibility of the adsorption was studied using Lagergren's kinetics equations of pseudo order equations of first and second order equations. Experimental investigation implies that the chromium removal follows pseudo-second order equation and it confines the investigation was subjected to time and concentration of chromium. The temperature effect was checked by chromium with Acacia Fumosa seed shell carbon. The Acacia Fumosa seed shell carbon alone was firmed using Gibbs free energy, enthalpy and entropy equations. The FTIR study of the synthesized activated carbon of before and after spectrum confirms the chromium adsorption. The SEM surface of the superficial layer change of carbon of initial and after chromium loaded state show viable change.

Acid Mine Drainage Precipitates from Mining Effluents as Adsorbents of Organic Pollutants for Water Treatment.

Acid mine drainage (AMD) is one of the main environmental problems associated with mining activity, whether the mine is operational or abandoned. In this work, several precipitates from this mine drainage generated by the oxidation of sulfide minerals, when exposed to weathering, were used as adsorbents. Such AMD precipitates from abandoned Portuguese mines (AGO, AGO-1, CF, and V9) were compared with two raw materials from Morocco (ClayMA and pyrophyllite) in terms of their efficiency in wastewater treatment. Different analytical techniques, such as XRD diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), N2 adsorption isotherms, and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) were used to characterize these natural materials. The adsorption properties were studied by optimizing different experimental factors, such as type of adsorbent, adsorbent mass, and dye concentration by the Box-Behnken Design model, using methylene blue (MB) and crystal violet (CV) compounds as organic pollutants. The obtained kinetic data were examined using the pseudo-first and pseudo-second order equations, and the equilibrium adsorption data were studied using the Freundlich and Langmuir models. The adsorption behavior of the different adsorbents was perfectly fitted by the pseudo-second order kinetic model and the Langmuir isotherm. The most efficient adsorbent for both dyes was AGO-1 due to the presence of the cellulose molecules, with qm equal to 40.5 and 16.0 mg/g for CV and MB, respectively. This study confirms the possibility of employing AMD precipitates to adsorb organic pollutants in water, providing valuable information for developing future affordable solutions to reduce the wastes associated with mining activity.

Maize stalks derived nanosilica: Synthesis, characterization and its kinetics in soil

Aim: The current study aimed to synthesize nanosilica from maize stalks at various calcination temperatures and to evaluate silicon release pattern in soil. Methodology: Nanosilica was synthesized by sol-gel method through thermal decomposition (500-700 oC) of maize stalks and evaluated for silicon release with varied levels (0, 5, 10, 15, 20, 30, 40 mg kg-1) through an incubation experiment and the data obtained was fitted in various kinetic models. Results: Nanosilica synthesized from maize stalks calcined at 700 oC showed spherical morphology with little agglomeration, amorphous nature and higher purity than the products obtained at 500 oC and 600 oC. Incubation experiment revealed that application of nanosilica at 40 mg kg-1 increased the available silicon upto 60 days with slight decrease at 80 days. The silicon release pattern from nanosilica was fitted in kinetic equations and observed that pseudo-second order equation describes the silicon release in a better way than other models. Interpretation: The present study showed a sustainable approach to convert maize stalks into valuable nanosilica, addressing the pressing issue of agri-waste management. The nanosilica synthesized from maize stalks calcined at 700oC exhibited promising characteristics and good silicon release pattern which can be alternatively used as a fertilizer source in agriculture. Key words: Agglomeration, Available silicon, Kinetics, Maize stalks, Nanosilica

New HCHO-scavenger for enhancing the HCHO-based adhesive in production environmentally friendly agro-based composites

Recently, green products are essential requirements. This work deals with synthesizing novel formaldehyde-scavenger based on black liquor to enhance the urea-formaldehyde (UF) adhesive for production of eco-friendly bio-composites. These HCHO-scavengers are synthesized from black liquor-based aerogel precursors. The assessment is carried out via estimating the HCHO adsorption capacities versus type of black liquor; as well as its beneficial effect on characterization of UF adhesive (Differential Scanning Calorimetry (DSC)-curing temperature; gel time and adhesive strength). The UF-scavenger system, which provides palm fiber-composite with properties (static bending, internal bond, and free-HCHO) compliance with the standard specifications is optimized. The data evidenced the effective role of black liquor (BL) from alkali pulping RS in presence of borohydride in resulting aerogel precursor of scavenger with higher HCHO-adsorption capacities (∼64 mg/g) than that produced from native aerogels (AG) in absence of BL. The kinetic adsorption is most applicable with the pseudo-second order equation. This observed behavior reflected on reducing the gel time and improved the bond strength of scavenger (Scv)-UF systems. It is interesting to note that all investigated BL-scavengers provide reduction in free HCHO of palm composites (from 30.7 mg/100g to 5–11 mg/g). These values are lower than that obtained from scavengers in absence of BLs (17.4 mg/100g). Based on the value of free-HCHO and mechanical properties, we recommend the scavenger resulted from black liquor of alkali pulping RS in presence of anthraquinone and borohydride (NaOH-AQ-BH) of screened RS as effective scavenger to provided eco-palm-wood composites with MOR, MOE, IB, free-HCHO and thickness swelling ∼ 27 MPa, 0.72 MPa, 7157 MPa, 7 % and 11 %, respectively. According to international standard specifications this type of palm-composite fulfills the grade H-3 and E1 according to environmental specification.

Performance of removing aqueous contaminant by zirconium based adsorbents: a critical review

The studies on materials for decontamination in aqueous solutions have increasingly received greater attentions. Such contaminants as heavy metals, arsenic, fluoride and phosphate are harmful to humans and aqueous species due to higher toxicity. Zirconium based adsorbents have become more attractive due to outstanding performance in decontamination. This article provides a comprehensive review of the performance and mechanisms of five types adsorbents: zirconium (hydro)oxides, zirconium hydrogen sulfate, zirconium based multiple metal typed adsorbents and zirconium impregnated complexes. The pseudo-first order and pseudo-second order equations and the intraparticle diffusion model can be applied in describing the adsorption kinetics, while Langmuir and Freundlich equations are the most commonly used adsorption isotherms. The important mechanisms for uptake of contaminants are: ligand exchange between adsorbate and adsorbent, surface complexation formation, and Lewis acid–base and electrostatic interactions. A series of successful studies demonstrate that the adsorbents are promising for removing aqueous contaminants.

The leaching behavior of heavy metal from contaminated mining soil: The effect of rainfall conditions and the impact on surrounding agricultural lands

Contaminated mining soils could lead to heavy metal pollution of surrounding farmlands under rainfall conditions. With the aids of sequential extraction, batch leaching, and dynamic leaching experiments, this study was carried out to investigate the characteristics of heavy metals in contaminated mining soils, understand their leaching behavior under different rainfall conditions, and evaluate the potential effects on surrounding farmlands. The results indicated that the concentrations of heavy metals (Cr, Ni, Cu, Zn, As, Cd, and Pb) in the contaminated mining soils were several or even twenty times higher than their corresponding background values, and Cd, Zn, Cu and Pb had considerable proportions (>50 %) in mobile forms. The leaching amounts of heavy metals from the contaminated mining soils had positive correlation with their contents in acid soluble form, and showed strong dependence on rainfall pH conditions. Acid rainfalls (pH = 4.32) can greatly increase the average annual release of Cd, Zn, Cu and Pb from mine soils in the study area, with increments ranging from 72.4 % (Pb) to 85.9 % (Cd) compared to those under alkaline conditions (pH = 7.42). The leaching of heavy metals was well fitted by two-constant, pseudo second-order and parabolic equations, indicating that their multi-layer sorption/desorption behavior on soil surface was dominated by chemical processes and their release was controlled by the diffusion within the soil pore channels. The two-column leaching experiment showed that the metal-rich leachate can lead to obvious increments of heavy metals in non-residual fractions (in particular Cd in acid soluble form) in surrounding farmlands, which would significantly raise the potential ecological risk associated with heavy metals. These findings indicate the importance of contaminated mining soils as a long-term source of heavy metals and the needs for mitigating the releases of toxic elements, especially in areas with heavy acid precipitation.

Novel chitosan–clay–iron nanocomposites supported on anodic aluminum as an efficient plate-shaped adsorbent for the removal of arsenic and dye from aqueous solutions

Design and synthesis of plate-shaped adsorbents supported on anodized aluminum as a substrate were successfully carried out for the adsorption of methyl orange (MO) and arsenic [As(V)] ions in aqueous solutions. Chitosan, clay, and iron was also used on the anodized aluminum as a substrate to make a nanocomposite adsorbent. The specific properties of the prepared samples were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Brunauer–Emmett–Teller (BET) analysis to determine the textural structure of the nanocomposites. The FESEM results showed that the formation of pores over the anodic surface was strongly related to anodizing time. Aluminum oxide and iron (hematite) phases were detected by XRD, which showed that the composite adsorbents were well synthesized. Isotherm adsorption was conducted using two models, of which the Langmuir model was in good agreement with the experimental results. The calculated maximum adsorption capacities based on the Langmuir equation for the adsorption of MO and As(V) ions were 53.48 and 14.70 mg/g, respectively. Pseudo first- and second-order models were used to demonstrate the adsorption mechanism of the anionic pollutants over the supported nanocomposites. The kinetic results indicated that the linearized pseudo second-order equation conformed best with the experimental data. The adsorption capacity was measured in six consecutive cycles to demonstrate the performance of the anodic adsorbent for removal of contaminants. The results illustrated 10 % and 15 % reductions in adsorption capacity of the anodized nanocomposite following six repeated cycles for MO and As(V) adsorption, respectively.

Removal of Aromatic Amino-derivatives from Aqueous Solutions Using Polymeric Supports Functionalized with Aminophosphonated/aminoacid-phosphonated Groups

Aromatic amines are the significant compounds used as intermediates in the organic synthesis, for obtaining such as azo dyes, antioxidants, fuel additives, corrosion inhibitors, pesticides, antiseptic agents, poultry medicine, and pharmaceutical synthesis. However, the presence of aromatic amines in water, even at very low concentrations, is extremely harmful to aquatic life and human health. Pollution of natural waters by aromatic amines is a serious environmental concern. The aim of this work was to obtain new adsorbents for use in the removal of aromatic amines from aqueous solutions. Styrene-15%divinylbenzene copolymers grafted with aminophosphonate groups (code: AP-S15%DVB) and amino acid-phosphonate groups (code: AM-S15%DVB) were used for the removal of pollutants such as: aniline, 2-methyl-aniline and 4-methyl-aniline. The adsorption capacity and the adsorption kinetic using the pseudo-first order and pseudo-second order equations were examined. From a kinetic point of view, it was established that the adsorption of the studied amino derivatives on the used adsorbents took place according to the pseudo-second order model. It was found that the adsorption rate constant increased with the increase of temperature, so the speed of the adsorption process increased. The obtained results confirm that the polymer adsorbents studied can be successfully used for the removal of aromatic amino derivatives from aqueous solutions for the purpose of wastewater treatment.

True Order Determination of Sonochemical Degradation Kinetics of Organic Contaminants in Water Using the Half-lives Method

In the literature, the modeling of the sonolytic decomposition kinetics of organic contaminants in water has been carried out using the pseudo-first and pseudo-second order equations. The results obtained with this method are totally biased because it requires the assumption of the order of the degradation reaction, which is a real limitation, and the sonochemical oxidation mechanism is a very complex phenomenon that cannot be described by such simple models. In this paper, for the first time, the true order of the sonochemical degradation kinetics of organic pollutants in aqueous solutions at various initial substrate concentrations was determined using the half-lives method combined with the general rate law model, i.e., the pseudo-nth order equation. Linear and nonlinear regression techniques were used to determine the order of the sonolytic destruction reaction. The half-life technique for the general rate law model can adequately describe the experimental results of the sono-destruction of the investigated pollutants. For rhodamine B and naphthol blue black, the sono-destruction mechanism for both contaminants does not change as the initial contaminant concentration varies over the range examined, while for 4-isopropylphenol and furosemide, the sono-destruction mechanism changes as the initial substrate concentration varies. A fractional order of the sonolytic destruction reaction was determined for all the pollutants tested. These fractional orders of sono-destruction reactions indicate the complex nature and behavior of the reactions, often involving multiple steps or mechanisms. They also reveal a more complex interaction between pollutant concentration and sonolytic destruction rate. In a word, the method developed in this paper should be used to determine the real order of the sono-oxidation reaction of nonvolatile organic pollutants in aqueous phase.

Equilibrium and kinetic studies in adsorption of H2S using coconut shell activated carbon xerogel: Effect of mass adsorbent and temperature

The presence of acid gases like hydrogen sulfide (H2S) in natural gas, refinery gas, and coal gas necessitates their removal from the gas stream to prevent corrosion of pipelines and production equipment and to ensure safety due to the toxic nature of H2S. A study was conducted to synthesize an adsorbent that is made from coconut shell which is modified to form coconut shell-activated carbon xerogel (CSACX). The main objective is to determine the kinetic models’ equation and adsorption isotherms that are most suitable for the adsorption of hydrogen sulfide by using CSACX. Two parameters were studied which were the adsorbent mass and the gas temperature. The adsorption process could be mathematically represented using the Thomas Model, Yoon-Nelson Model, and Adam-Bohart. It is expected that the adsorption process is mathematically represented using the Thomas and Yoon-Nelson Model for both the effect of mass of adsorbent and effect of gas temperature. The kinetic models used were Pseudo-First Order and Pseudo-Second Order. Suitability of equation was determined by correlation coefficient (R2). The higher the R2, the more suitable the equation is to process. It is expected that the adsorption processes using the CSACX fit both pseudo-first and pseudo-second order equation. This means that both physisorption and chemisorption occur during the adsorption process.

Sulu Çözeltide Tetrasiklin Giderimi için Fındık ve Antep Fıstığı Kabuklarının Eş-karbonizasyonundan Elde Edilen Yeni Hidrokömürün Kullanımı

In present work, the use of a new hydrochar (HSPSHC) produced by the combined hydrothermal carbonization (co-HTC) of hazelnut and pistachio shells (HS and PS) as a sorbent material in tetracycline (TC) antibiotic removal from water was investigated. It was obtained from hydrothermal carbonization of HSPSHC, hazelnut and pistachio shells by mixing 1:1 by mass at 220 oC for 6 h. Mass yield, energy density and higher heating value parameters were calculated for HSPSHC, and the surface chemistry was characterised using Fourier transform infrared spectroscopy (FTIR). TC adsorption on HSPSHC was carried out by kinetic and isotherm studies using batch method. The experimental kinetic results were qualified in pseudo first-order (PFO) and second-order (PSO) kinetic equations and it was observed that the adsorption complied with the PSO kinetics. The experimentally obtained results were applied to Langmuir and Freundlich model equations and isotherm modeling was performed. The adsorption isotherm of TC on the prepared hydrochar was well fitted by the Langmuir equation, which yielded a maximum monolayer adsorption capacity of TC of qm: 137.06 mg/g at 323 K and pH 4.0 on the HSPSHC hydrochar. In addition, thermodynamic studies revealed that the adsorption of TC by HSPSHC is spontaneous and is an endothermic process.

Microwave-assisted one-pot method preparation of ZnO decorated biochar for levofloxacin and Cr(Ⅵ) removal from wastewater

ZnO based-double functional biochar (ZnO-BC) derived pine sawdust is prepared by microwave heating using simple one-pot method for levofloxacin (LEV) and Cr(Ⅵ) removal from wastewater. ZnO-BC has well developed pore structure with BET surface area of 915.47 m2/g, which also has well ZnO crystalline. These characteristics make ZnO-BC available as the adsorbent and photocatalyst for LEV and Cr(Ⅵ) removal wastewater. LEV and Cr(Ⅵ) adsorption date fit well with the Hill and Pseudo-second order equation with LEV and Cr(Ⅵ) adsorption amount of 193.42 and 21.03 mg/g, respectively. The LEV and Cr(Ⅵ) adsorption behavior are determined by the chemisorption process. The hydrogen bond, π-π interaction, surface complexation, pore filling are responsible for LEV removal. While the hydrogen bonding, complexation and redox are crucial to the removal of Cr(Ⅵ) from wastewater. LEV removal is 85.72–97.19% at 15–25 mg/L at 120 min, and Cr(Ⅵ) removal is 72.62–99.9% at 40–60 mg/L at 75 min under UV irradiation. The possible photocatalytic mechanisms of the LEV and Cr(Ⅵ) are further investigated and analyzed.

Biosynthesis of iron oxide nanoparticles at different temperatures and its application for the removal of Zinc by plant mediated nanoparticle, as an eco-friendly nanoadsorbent

Surface and underground water sources are threatened by various pollutants every day. Due to the fact that heavy metals do not disappear, their presence in the environment is very dangerous. Therefore, in this study, iron oxide nanoparticles were synthesized using Aloe vera extract and their application for Zinc removal from aqueous solution was studied. Nanoparticles were synthesized in different temperature conditions of 25 °C and 90 °C. The synthesized nanoparticle characteristics were identified using SEM, EDX, XRD, BET surface area, FTIR and UV–visible Spectroscopy. The SEM images indicated that the iron oxide nanoparticles synthesized at 25 °C and 90 °C had spherical morphology with average particle diameter 62.96 nm and 65.34 nm and based on BET results with a specific surface area of 37.450 and 42.520 m2 g−1, respectively. Adsorption of Zn(ΙΙ) in aqueous solution on the surface of synthesized nanoparticles was investigated and the highest adsorption efficiency was obtained at pH = 7, T = 25 °C, adsorbent concentration = 0.3 g/L, contact time = 90 min, adsorbed concentration = 10 mg/L. The adsorption fitted the pseudo second-order kinetic rate equation well, which confirmed that adsorption was via chemisorption. Freundlich model compared to Langmuir model can better describe the adsorption behavior of Zinc with iron oxide nanoparticles. Nanoparticles synthesized at 90 °C had a more uniform structure and higher absorption capacity. The absorption efficiency of 99 % was observed for nanoparticles synthesized.

Mechanistic understanding of the enhanced adsorption of diclofenac on a heat-treated and acid-leached halloysite

ABSTRACT Diclofenac (DCF), a common nonsteroidal anti-inflammatory drug, is frequently detected in aquatic environments, causing serious threat to aquatic organisms and humans through bioaccumulation, persistence, and toxicity. Using eco-friendly clay-based adsorbents, samples of halloysite (H) processed at 600°C (H600-0N) and then HCl-leached with 3 N concentration (H600-3N) were prepared, characterised by Inductively Coupled Plasma (ICP), N2 adsorption – desorption, and infrared spectroscopy with Fourier transform (FTIR), and used in DCF adsorption. H600-3N exhibited a substantial surface area increase from 63 m2 g−1 for H to 434 m2 g−1 due to an elevated SiO₂/Al₂O₃ ratio of 23.83 against 1.72 for H. In this context, H600-3N and H adsorbed 165 mg g−1 and 37.9 mg g−1 of DCF, respectively. The isotherms of H600-xN(x = 0 or 3) were adequately adjusted to the Langmuir-Freundlich model, while the kinetic data were suitably described by the pseudo-second order equation. Through cross-checking the results of characterisation, DCF adsorption and the FTIR investigation between DCF and H600-3N, a mechanism has been suggested that includes two main components: hydrogen bonding between the silanol’s hydrogen atom and the negatively charged carboxylate anion and hydrophobic interactions between the – Si – O – Si – entities and the DCF aromatic rings. The elucidation of intermolecular interactions between organic contaminants and 1:1 clay minerals is essential to develop the application of these abundant and low-cost materials in wastewater treatment.

Application of the general rate law model to the sonolytic degradation of nonvolatile organic pollutants in aqueous media

The pseudo-first and pseudo-second order equations have been the most commonly used models to characterize the sonolytic disappearance kinetics of nonvolatile pollutants in aqueous media. In this work, the general rate law model, i.e., pseudo-nth order kinetics equation, was applied for the first time to the sono-decomposition of different nonvolatile organic pollutants, naphthol blue black (NBB), furosemide (FSM), 4-isopropylphenol (4-IPP), and rhodamine B (RhB), in water. It was shown that the general rate law for a chemical reaction would apply to the kinetics of sonochemical decomposition. It is not feasible to set the order of ultrasonic pollutant degradation kinetics to pseudo-first or pseudo-second, as is typically used in numerous studies. The sonochemical oxidation reaction has a fractional order, the order is often non-integer, which frequently indicates a complex sonolytic decomposition reaction mechanism. The degradation mechanism of NBB and RhB does not change with the initial substrate concentration. They are ultrasonically degraded by hydroxyl radicals both in the bulk liquid solution and at the liquid/bubble interfacial layer. The destruction mechanism of FSM and 4-IPP changes as the initial contaminant concentration changes. At low initial substrate concentrations, these pollutants are oxidized mainly by reaction with hydroxyl radicals in the bulk liquid solution and at the interfacial shell of the cavitation bubbles. At high initial substrate concentrations, FSM and 4-IPP are degraded by thermal destruction in the liquid/bubble interfacial layer and by •OH radicals both in the bulk liquid solution and at the liquid/bubble interfacial layer. Additionally, the pseudo-nth order model predicts very well the sonolytic degradation at various sonication frequencies and intensities. The general rate law expression should be used to assess the real kinetics order of the sonolytic destruction process without any predetermined assumptions or constraints.

Amino-carboxyl cellulose for adsorption of Cd2+ and Pb2+

An amino-carboxyl cellulose was synthesized using the grafting of glycine on the aldehyde cellulose through a Schiff base reaction for the adsorption of heavy metals with Cd2+ and Pb2+ as the representative. Higher affinity of the amino-carboxyl cellulose was found at pH 4.5–5.0 for Cd2+ and 4.0–5.5 for Pb2+. The equilibrium was achieved within 30 min. The adsorption capacities of amino-carboxyl cellulose (Cd2+: 85.7 mg g−1, Pb2+: 115.1 mg g−1, Cu2+: 68.2 mg g−1, Co2+: 60.1 mg g−1, Ni2+ 48.5 mg g−1 and Zn2+: 52.8 mg g−1) at 30 °C were observed. A mild increase in the adsorption capacities of Cd2+ and Pb2+ from 15 to 45 °C was observed. Adsorption data correlated well with the Langmuir and pseudo-second order equations, illustrating chemisorption of Cd2+ and Pb2+ by the amino-carboxyl cellulose. The adsorption of the amino-carboxyl cellulose for Cd2+ and Pb2+ was a spontaneous and endothermic. The amino-carboxyl cellulose owned a high reusability after 4 cycles.