Pseudo-second Order Kinetic Equation Research Articles

An investigation into the effect of UV irradiation and biofilm colonization on adsorption and desorption behavior of polyurethane (PU) microplastics for bisphenol A (BPA)

Recent studies have demonstrated that microplastics (MPs) can act as a transport vector for pollutants in the environment. However, most studies have focused on carbon-carbon backbone polymers, with little known about heteroatom backbone polymers. In this study, polyurethane (PU) MPs were modified by UV irradiation and microorganism colonization to assess the different aging treatments on the interaction behavior (adsorption/desorption) between PU MPs and bisphenol A (BPA). The results of the adsorption kinetics experiment illustrated that the adsorption process of BPA could be described well by a pseudo-second order kinetic equation on both fresh and aged PU MPs. Although fresh PU MPs revealed the highest saturated adsorption capacity, at low BPA exposure concentrations (≤ 100 μg/L) the adsorption capacities for UV aged and biofilm colonized PU MPs were very similar to fresh MPs or even slightly higher than for fresh MPs, the main adsorption mechanisms including H-bonding interactions and π–π interactions. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) investigations suggested obvious physicochemical property changes (e.g., generation of new functional groups, erosion, etc.) after UV irradiation and biofilm colonization. This study also showed that different exposure environments (ultrapure water, artificial seawater, simulated gastric fluid) could affect BPA adsorption/desorption via hydrophobic and electrostatic interaction on PU surfaces. These results further clarify the adsorption mechanisms of BPA on PU MPs that have undergone different aging treatments, and provides a theoretical basis for the assessment of environmental behavior and exposure risks when PU MPs and BPA coexist.

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.

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.

Assessment of Cu(II) Removal from Aqueous Solutions by Modified Pomelo Peels: Experiments and Modelling.

In this study, low-cost pomelo peel wastes were used as a bio-sorbent to remove copper ions (e.g., Cu(II)) from aqueous solutions. Prior to testing its Cu(II) removal capability, the structural, physical and chemical characteristics of the sorbent were examined by scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, and Brunauer-Emmett-Teller (BET) surface area analysis. The impacts of the initial pH, temperature, contact time and Cu(II) feed concentration on the Cu(II) biosorption using modified pomelo peels were then assessed. Thermodynamic parameters associated to the biosorption clearly demonstrate that this biosorption is thermodynamically feasible, endothermic, spontaneous and entropy driven. Furthermore, adsorption kinetic data were found to fit very well with the pseudo-second order kinetics equation, highlighting that this process is driven by a chemical adsorption. Finally, an artificial neural network with a 4:9:1 structure was then established for describing the Cu(II) adsorption using modified pomelo peels with R2 values close to 0.9999 and to 0.9988 for the training and testing sets, respectively. The results present a big potential use of the as-prepared bio-sorbent for the removal of Cu(II), as well as an efficient green technology for ecological and environmental sustainability.

Siirt Koçpınar Karışık Tip Kil ile Ni (II) İyon Adsorpsiyonu İçin Pseudo-İkinci Kinetik Derece Modelinden Elde Edilen Lineerleştirilmiş 6 Tip Denklem ile Deneysel Verilerle Kinetik Model Doğrulaması

Bu çalışmadaki temel amaç Ni (II) iyonlarını sulu çözeltilerden uzaklaştırmaktır. Bunun için adsorplayıcı olarak karışık tip kil kullanılmıştır. Kilin karakterizasyonunu belirlemek için, SEM, XRD ve XRF analizleri yapılmıştır. Bu analizlerden elde edilen sonuçlar, kilin karışık tipte olduğunu göstermiştir. Siirt ili Koçpınar bölgesinden alınan kilin yapılan SEM analizinde; doğal kilin genelde küresel şekilli ve amorf yapıda olduğu ve Ni(II) ile muamele edilen kilin dağınık morfolojiye sahip olduğu görülmüştür. Kullanılan kilin analiz sonuçlarına göre; Muskovit: %32, Plajioklaz: %15, Kalsit: %15, Kuvars: %9, kil mineralleri: %29 oranında olduğu, detay kil analizinde ise; kil mineralinin bileşenleri: illit: % 17, klorit: %62, montmorillonit: %21 oranında olduğu tespit edilmiştir. XRF analiz sonuçları literatüre yakın olmakla beraber, kil karışık tipte olduğu için mineral oranlarında kaymalar gözlenmiştir. CaO oranının yüksek olması SiO2 oranını düşürmüştür.
 Yalancı-ikinci dereceli (pseudo-second order) kinetik model, adsorplayıcı ve adsorplanan madde arasındaki adsorpsiyon mekanizmasını açıklamak için, yaygın olarak kinetik çalışmalardan elde edilen verilere uygulanmaktadır. 
 Bu araştırmada 298 K sıcaklığında yapılan deneyden elde edilen veriler, yalancı – ikinci dereceli kinetik modelinin 6 lineer tipine uygulanmıştır. Bu veriler ışığında grafikler oluşturularak, R2, K2 ve qe değerleri hesaplanmıştır. Modele uyum sırasının Tip 2 = Tip 5

A mechanistic insight into the shrinkage and swelling of Ca-montmorillonite upon adsorption of chain-like ranitidine in an aqueous system

Adsorption behavior of ranitidine hydrochloride (RT) on a Ca-montmorillonite (SAz-1) was studied in aqueous system through batch experiments. The adsorption kinetics revealed that the equilibrium reached within 0.25 h and the data fitted well to the pseudo-second order kinetic equation (R2 = 0.98). The maximum RT adsorption capacity of SAz-1 was 369.2 mg/g and the adsorption isotherm data followed the Langmuir model (R2 = 0.99). The adsorption of RT and desorption of exchangeable cations from the clay mineral were linearly correlated, suggesting that cation exchange was the dominant mechanism of RT adsorption. The XRD examination of RT-adsorbed SAz-1 samples (unsaturated/saturated) after heating enabled the calculation of RT occupied area in the interlayer of the clay mineral. The results suggested that adsorbed-RT at low loading rate could lay on the internal surfaces in a free style to reduce the basal spacing (d001 value) of SAz-1. When the RT loading rate was increased, a limited surface space enforced more RT molecules to lay in a tilted style and caused interlayer swelling of SAz-1 increasing the d001 value. The trend of rising decomposition temperature of RT with increasing RT loading rates confirmed intercalation of RT molecules in SAz-1. Infrared spectral analysis revealed the participation of amide and furan groups of RT in binding between RT and SAz-1. Thus, this study indicated that SAz-1 is an efficient adsorbent to remove RT from contaminated water, and the chain-like molecular structure of RT could cause an irregular change in the basal spacing of swelling type clay minerals.

Removal of Pb<sup>2+</sup> from aqueous solution using sericite from Son Binh, Ha Tinh

Sericite sample from Son Binh, Huong Son, Ha Tinh was used to remove Pb2+ ion from aqueous solution. The effects of factors including pH, contact time, mass of serisite and Pb2+ initial concentration on the adsorption Pb2+ efficiency and capacity were investigated. The results showed that the adsorption capacity and removal efficiency of Pb2+ reached 2,54 mg/g and 89 % at the suitable conditions: 0.7g sericite, Pb2+ intinal concentration of 40 mg/L and contact time 60 minutes at room temperature (25°C) and pH0 5,3. The adsorption process follows the Langmuir adsorption isotherm model with the maximum monolayer adsorption capacity of 5.52 mg/g and follows the pseudosecond-order kinetic equation.

Efficient removal of methyl orange using magnesium oxide nanoparticles loaded onto activated carbon

ABSTRACT. In this work, an activated carbon composite made with magnesium oxide nanoparticles (MgONP-AC) was effectively utilized for methyl orange (MO) adsorption. The effect of pH (6-10), mass of MgONP-AC (0.1-0.3 g/L), initial MO concentration (10-30 mg/L), and temperature (283-323 K) on MO removal was investigated using a central rotatable composite experimental design based on the response surface technique (RSM) at an equilibrium agitation period of 60 min. The studies predicted the optimal MO removal of 98.99% at pH 7.68, MgONP-AC dosage of 0.24 g/L, and starting MO concentration of 15 mg/L, and temperature of 313 K. Furthermore, an artificial neural network (ANN) was utilized to simulate MO adsorption, and it properly predicted MO removal using mean squared error (MSE) and R2 for the testing data. The ANN predicts a maximum removal of 99.63% with ANN with R2 = 0.9926. The kinetic results suited the pseudo-second order kinetic equation, and the data from the equilibrium investigations corresponded well with the Langmuir isotherm (maximum uptake capacity qmax = 346 mg/g). Endothermic, spontaneous, and physical adsorption were discovered during the thermodynamic investigations.
 
 KEY WORDS: Adsorption, Artificial neural network, Experimental design, isotherms, Kinetics, Methyl orange, MgONP-AC
 
 Bull. Chem. Soc. Ethiop. 2022, 36(3), 531-544. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i3.4

Theorithecal and experimental study on the thermodynamic parameters and adsorption of methylene blue on “Argania shells” in industrial waters

The present work consists in studying the kinetic, isothermal and thermodynamic properties related to the adsorption of Methylene Blue in industrial waters. The study proposes an package to study the adsorption on the side calculating the parameters: (Langmuir constant KL, Frendlich constant KF, the rate constants for a first order K1, pseudo-second order K2 and second order kinetic K3, and paramètres thermodynamiques) and plotting the trends, through a user-friendly graphical interface. This package aims to save time and avoid errors that may occur when processing experimental results. The experimental study of methylene blue adsorption on Argan shells was performed to verify the performance of this package. The experimental study of the adsorption of methylene blue on the shells of Argan was carried out to verify the performance of this set. It is found that the amount of adsorption of methylene blue on the shells of Argan is 90.96 mg / g for an estimated equilibrium time of 240 min. The correlation coefficient showed that the pseudo-second order kinetic equation best describes the adsorption kinetics. The experimental equilibrium data were analyzed, the Langmuir isotherm provided the best correlation. In addition, the determination of the thermodynamic parameters shows that the reaction is spontaneous and exothermic.

Removal of Fe2+ and Mn2+ from Polluted Groundwater by Insoluble Humic Acid/Tourmaline Composite Particles.

Insoluble humic acid/tourmaline composite particles (IHA/TM) were prepared by combining inorganic tourmaline (TM) with the natural organic polymer humic acid (HA) and carbonizing them at 330 °C to study the removal characteristics and mechanism of Fe2+ and Mn2+. The results showed that the optimal ratio of TM to IHA is 2:3. When the temperature of the IHA/TM composite particles was 35 °C and the pH was 6, the adsorption of Fe2+ and Mn2+ by IHA/TM reached equilibrium at 240 min. The optimum dose of the adsorbent was 10 g/L, and the equilibrium adsorption capacities of Fe2+ and Mn2+ were 5.645 mg/g and 3.574 mg/g, respectively. The process of IHA/TM adsorption of Fe2+ and Mn2+ in water was spontaneous, endothermic and sustainable, and cooling was not conducive to adsorption. The pseudo-second order kinetic equation can well reflect the adsorption mechanism of IHA/TM on Fe2+ and Mn2+, and the Langmuir adsorption model better describes the isothermal adsorption behaviour. The material characterisation and adsorption experiments indicate that surface coordination and chemical precipitation are the main mechanisms of Fe2+ and Mn2+ removal by IHA/TM.

Removal of Copper(II) in the Presence of Sodium Dodecylobenzene Sulfonate from Acidic Effluents Using Adsorption on Ion Exchangers and Micellar-Enhanced Ultrafiltration Methods.

The selective removal of Cu(II) in the presence of sodium dodecylobenzene sulfonate from acidic effluents was made using the adsorption and micellar-enhanced ultrafiltration methods. Lewatit MonoPlus TP220 showed the best adsorption behavior in the systems containing Cu(II) in the presence of ABSNa50 surfactant compared to the other adsorbents (removal efficiency ≈ 100%, sorption capacity ≈ 10 mg/g). The kinetics followed the pseudo-second order kinetic equation. The Langmuir adsorption capacities were 110 mg/g (the system with ABSNa50 above CMC) and 130.38 mg/g (the system with ABSNa50 below CMC). The working ion exchange capacities were Cw = 0.0216 g/mL and Cw = 0.0135 g/mL. The copper removal by the micellar-enhanced ultrafiltration method was 76.46% (0.1 mol/L HCl).

Feasible synthesis of coal fly ash based porous composites with multiscale pore structure and its application in Congo red adsorption

Facing the great challenge that the increasing solid waste fly ash is difficult to treat and utilize properly, this paper reports a class of novel low–cost fly ash porous materials with high interconnected porosity fabricated by a facile foaming process. On this basis, composites with multiscale pore structures from the nanometer to macroscopic scale were designed and constructed by decorating layered double hydroxide (LDH) onto the inner channel surface. Such porous materials with 3D through–hole structures showed high interconnected porosity (up to 77.61%), suitable compressive strength (up to 23.79 MPa) and significant water permeation flux (549.86 m3∙m−2∙h−1 at 0.1 MPa). Moreover, the adsorption effect of dosage, initial concentration, pH, temperature and contact time on Congo red (CR) from simulated wastewater was investigated. The composites exhibited a good adsorption efficiency of ∼100% and adsorption capacities of 45.79 mg/g. The adsorption kinetic can be explained well by the pseudosecond–order kinetic equation and isotherm adsorption followed Langmuir isotherm model. This suggests that low–cost and eco–friendly fly ash composites have potential applications in industrial–scale wastewater treatment. This work also provides a general strategy to design and utilize fly ash porous materials for filtration and adsorption.

Performance of sesame straw cellulose, hemicellulose, and lignin biochars as adsorbents in removing benzo(a)pyrene from edible oil

The safety problems related to the occurrence of benzo(a)pyrene in edible oil have been a major threat to human health, and now significant attention has been to remove benzo(a)pyrene. So in this work, cellulose, hemicellulose, and lignin biochars were prepared, and then were used to remove benzo(a)pyrene from contaminated oil. Based on the nitrogen adsorption/desorption isotherms and the scanning election micrographs, the modified biochars had a huge specific surface area of 983.50-1915.55 m2/g and a well-developed porous structure. The modified biochars showed higher removal rate for benzo(a)pyrene than unmodified biochars. The highest adsorption (95.79%) of benzo(a)pyrene was achieved using the modified lignin biochar, which was therefore selected for evaluation of adsorptive capacity. The ability of the modified lignin biochar to adsorb benzo(a)pyrene was consistent with the pseudo-second order kinetic equation indicating mainly chemisorption, and it fit the Freundlich isotherm (R2 > 0.999), thereby revealing the occurrence of multilayer adsorption. The effect of π-π conjugation interaction and pore-filling together promoted the high adsorption performance of the modified lignin biochar. This work demonstrates that the modified lignin biochar could be a promising adsorbent for the removal of benzo(a)pyrene from edible oils.

An in situ grown amorphous ZrO2 layer on zeolite for enhanced phosphate adsorption.

Zeolite supported amorphous metal oxide nanolayers with high specific surface area, abundant adsorption sites, and excellent reusability hold a bright prospect in the efficient removal of contaminants, yet it is proven to be still challenging to precisely regulate and control their synthesis. Herein, we reported a facile synthetic strategy for rational design and achieving the uniform and firm in situ growth of an amorphous ZrO2 layer decorated on the surface of zeolite (ZEO@AZ) for enhanced phosphate adsorption. The Langmuir isotherm model and pseudo-second order kinetic equation well described the adsorption process towards phosphate solution, and the synthetized ZEO@AZ exhibited an excellent maximum adsorption amount of 24.98 mgP g−1. Furthermore, the adsorption of phosphates on ZEO@AZ was confirmed to be chemisorption, endothermic and spontaneous. This approach for fabricating amorphous metal oxide nanolayers on a robust matrix may provide a new route for constructing composites with superb phosphate adsorption performance.

Carboxylate-functionalized hollow polymer particles modified polyurethane foam for facile and selective removal of cationic dye

As an efficient technique for treatment of dye contaminated water, adsorption process has drawn wide research attention. However, conventional sorbents are mainly powdery and difficult to separate, which severely limited their practical application. Herein, a series of polyurethane foam (PUF) modified with carboxylate-functionalized hollow polymer particles (HPPs-COO-) were specially designed and synthesized. Combining the advantages of both open-cell foams and functional HPPs, the as-prepared HPPs-COO-/PUF can be utilized as advanced adsorbents towards cationic dyes (i. e., methylene blue b-MB). Batch adsorption experiments were performed to evaluate and optimize various parameters affecting the adsorption performance of HPPs-COO-/PUF, including the content (mass ratio) of HPPs-COO-, initial b-MB concentration, and solution pH. The experimental data demonstrated that the adsorption isotherm results fitted well with Langmuir model, possessing maximum sorption capacity of 125 mg/g at pH = 10 (25 °C). Furthermore, the adsorption process was better described by the pseudo-second order kinetic equation. Besides, the HPPs-COO-/PUF exhibit a remarkable pH-sensitive sorption capacity. When the pH value changed from 10.0 to 2.0, the sorption capacity of HPPs-COO-/PUF dropped sharply from 115.6 mg/g to 26 mg/g. Hence, regeneration of b-MB containing HPPs-COO-/PUF can be effectively realized. The recovered HPPs-COO-/PUF show > 90% b-MB removal efficiency during five adsorption–desorption processes, demonstrating excellent recyclability. With advantages of facile preparation, high adsorption capacity, and outstanding reusability, the HPPs-COO-/PUF showed great potential for dye wastewater treatment.

Adsorption and reduction of carcinogenic organics by ordered semi-crystalline poly-m-chloroaniline

Poly-m-chloroaniline has been synthesized by chemical oxidative polymerization of m-chloroaniline and confirmed by spectroscopic studies. Powder X-ray diffraction and FESEM studies confirmed ordered arrangement in poly-m-chloroaniline. The peak at lower angle such as 7.09° having d spacing of 12.53 Å shows ordered structure of PmClA which was further confirmed by layered morphology in the FESEM images. FTIR spectra confirm the stretching and vibration mode of polymeric m-chloroaniline ring. BET surface area and pore diameter of PmClA were found to be 121 m2/g and 15.184 nm. Poly-m-chloroaniline was found to have better adsorption capacity toward anionic dyes over cationic dyes. The anionic dye (IC and EY) was 98 and 99% removed in just 25 min, whereas the cationic dye (MG and Rh6G) was 87 and 83% removed in 30 min. Langmuir adsorption isotherm model and pseudo second-order kinetic equation fitted the data best. Mechanism of adsorption has also been proposed. This is suggested that polymeric materials can be used for purification of water. The reduction of aromatic nitro compounds to amino compounds using organocatalyst has been done for the first time.

Promotion effect of Ce doping on MgO-based adsorbents for CO2 adsorption performances

This paper presented the effect of Ce doping on the structure, morphology and CO2 adsorption performances of MgO-based adsorbents. Nano MgO-based adsorbents were synthesized by citric acid complexation method using Mg(NO3)2·6H2O and Ce(NO3)3·6H2O as the precursors, and characterized by XRD, SEM, N2 adsorption/desorption and FT-IR techniques, respectively. The results demonstrated that with Ce incorporation, the crystal sizes of the adsorbents were obviously reduced, and a large number of micropores and mesopores were formed. The CO2 adsorption of the samples was carried out on a thermogravimetric analyzer, and the adsorption data were fitted by the first-order kinetic equation, the pseudo second-order kinetic equation and the intra-particle diffusion model, respectively. It can be concluded after Ce doping, the adsorption capacity of the adsorbent was greatly improved, due to good dispersity of MgO particles and well-developed porosity, and the increase of the surface reaction rate could be attributed to the increase of BET surface area and the alkaline sites of the Ce-incorporated adsorbents, while the increase of the rate in the diffusion stage was caused by the formation of the porous structure. Therefore, the smaller the crystal size of MgO, the more favorable it was for CO2 capture. This work provided the inspiration of MgO-based adsorbent for improving CO2 adsorption.

Adhesion evaluation of the Rhodococcus opacus strain on an apatite surface

Adsorption of microorganisms and/or their different components onto a mineral surface would modify the surface characteristics of the mineral. Thus, this investigation evaluated the adsorption capacity of the Rhodococcus opacus strain onto an apatite surface. Zeta potential and contact angle measurements of the mineral showed dislocations of the values after interaction with the microorganism. The maximum adsorption density reached was 24.10 mg of bacterial cells per gram of mineral using a biomass concentration of 400 mg/L. The experimental data were linearly fitted by the Freundlich model and the adsorption density as a function of time was linearly fitted by the pseudo-second order kinetic equation. The results showed that the bacterial strain has affinity for the apatite surface and ability to make it hydrophobic.

Roles of initial bacterial attachment and growth in the biofouling development on the microfiltration membrane: From viewpoints of individual cell and interfacial interaction energy

In this study, bacterial adhesion and growth behaviors during biofouling development on the polyvinylidene fluoride (PVDF) microfiltration (MF) membrane were investigated. It is recognized that abundance of biomass is essential to the serious biofouling occurrence. The irreversible resistance of membrane increased to 5.2 × 1011 m−1 after filtration of 22 days, and then to 1.42 × 1012 m−1 at the end of 68 days. The growth of bacteria on the membrane surface conformed well to the pseudo second-order kinetic equation, and was mainly determined by the substrates concentration in the feeding. Based on the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory, the interfacial energy between MF membrane and typical bacteria (Pseudomonas aeruginosa) decreased continuously from 11800 KT (0 h) to −8100 KT (16 h), and the energy barrier decreased gradually after short-term filtration. By chemical cleaning with NaClO and NaOH, the flux of MF membrane recovered to 92.3% and 80.2% of the initial flux, respectively, but the interface energy between membrane and bacteria decreased to −2550 KT and −280 KT, respectively, which accelerated the adhesion of bacteria. This work helps to understand the biofouling mechanisms and provides guidance for the mitigation and control of biofouling for membrane filtration.

Synthesis, characterization, and flocculation performance of cationic starch nanoparticles

A series of cationic starches with different degrees of substitution were synthesized by etherification of potato starch with 3-chloro-2-hydroxypropyl trimethylammonium chloride (CTA). Cationic starch nanoparticles (CTA-StNPs) with different sizes were prepared by precipitation. Flocculation behaviors of the CTA-StNPs in simulated water sample containing kaolin were studied. The results showed that the dosage required to bring the simulated water sample containing kaolin to attain maximum transmittance at pH = 4 was significantly less than that at pH = 7. Both the size and degree of substitution of the CTA-StNPs affected their flocculation performance. The smaller the size and the higher the degree of substitution of CTA-StNPs, the better was the flocculation performance. Charge neutralization played a leading role in the flocculation process. The adsorption process of the CTA-StNPs onto kaolin could be divided into rapid adsorption, stable adsorption and equilibrium adsorption and followed pseudo second-order kinetic equation very well (R2 > 0.99).