Dye Removal Rate Research Articles

Adsorption of Safranin dye, an emerging contaminant from wastewater by modified bamboo (Bambusa Tulda): Characterization and column model analysis

AbstractA fixed‐bed column study was studied to assess the performance of sodium bicarbonate modified Bambusa Tulda to remove Safranin from wastewater. Fourier Transform Infrared Spectroscopy analysis shows the existence of carboxyl as well as hydroxyl bonding and grouping. Scanning Electron Microscope analysis shows the enhanced structure of Bambusa Tulda before and after chemical modification, and Energy dispersive X‐ray analysis shows the existence of Na, O after chemical modification with sodium bicarbonate. The maximum removal was found at higher bed depth and low flow rate. The breakthrough analysis time and exhaust time increase with an increase in bed height. At 5 ml/min flow rate, with initial concentration of 50 mg/L and bed height of 15 cm of adsorbent, shows best removal rate of safranin dye in column analysis. The Bed Depth Service Time (BDST) model and Thomas model analysis remained similar with experiment results, which indicates that they are suitable for the design of column study. It is being concluded that sodium bicarbonate modified Bambusa Tulda is an effective, low cost and readily available adsorbent for the adsorption of Safranin from wastewater.

Synthesis and Characterization of SiO2/TiO2 as Photocatalyst on Methylene Blue Degradation

The paper presents a modification of titanium dioxide with fumed silica. The SiO2/TiO2 photocatalysts were obtained by the sol-gel method and then were calcined under an argon atmosphere. Various SiO2 weights (2–17.2 wt.%) were used in the materials’ preparation stage. The obtained samples were characterized using advanced analytical methods, such as FT-IR/DRS infrared spectroscopy, X-ray diffraction, SEM scanning electron microscopy, and UV-Vis/DRS spectroscopy. The BET specific surface area and zeta potential of samples were also measured. Based on the obtained results, it was observed that the modification of titanium dioxide with SiO2 effectively inhibited the increase in crystallite size of anatase and brookite during calcination and the decrease in specific surface area values. Moreover, the presence of SiO2 in the nanomaterials contributed to the increase in the size of specific surface area and the change in band gap energy values. The photocatalytic activity was determined based on the decomposition of methylene blue under UV irradiation. Thermal modification in an inert gas atmosphere significantly increased the dye removal rate. It should be noted that all the obtained SiO2/TiO2 photocatalysts showed higher activity compared to the starting TiO2. It was also found that the photocatalytic activity increased along with the increase in SiO2 content in the sample (up to 14.3 wt.% of SiO2). The highest activity was recorded for SiO2(11.1%)/TiO2_400 and SiO2(14.3%)/TiO2_400 samples.

Removal of Malachite Green Dye from Aqueous Solution by Catalytic Wet Oxidation Technique Using Ni/Kaolin as Catalyst.

In this study, natural Algerian kaolin was used as a support and impregnated with nickel at different loading amounts (2 wt.%, 5 wt.%, and 7 wt.%) in order to prepare a supported catalyst. The wet impregnation technique was used in this preparation; nickel oxide (NiO) was the active phase precursor of the catalyst, and the catalysts were designated as follows: 2%, 5%, and 7% Ni/kaolin. These catalysts were put to the test in catalytic wet peroxide oxidation (CWPO) for degrading the organic contaminant malachite green dye (MG). Analytical techniques such as FTIR spectroscopy, X-ray diffraction, BET, and X-fluorescence were used to examine the structure, morphology, and chemical composition of the support and the produced catalysts. Several parameters, including temperature, catalytic dose, metal loading, hydrogen peroxide volume, and kinetic model were systematically investigated. The combination of improved parameters resulted in a significant increase in the catalytic activity, achieving a high removal rate of MG dye of 98.87%.

Effective removal of Orange II dye by porous Fe-base amorphous/Cu bimetallic composite

Azo dye wastewater is a worldwide problem with substantial deleterious environmental effects. Fe-based amorphous alloys have shown potential in azo dye wastewater treatment. However, their slower degradation rate and narrow working pH range hinder their wide application. Therefore, we designed a new porous Fe-base amorphous/Cu (Feam/Cu) bimetallic composite ribbon and prepared them using the chemical replacement copper plating method to remove the Orange II dye. The designed bimetallic composite ribbons can enhance the removal rate of azo dyes to various extents. The kinetic reduction rate (kobs) of the porous Feam/Cu bimetallic composite is 0.217 min−1 at pH= 7, a 92 % improvement compared to the kobs of Feam. Moreover, the porous Feam/Cu bimetallic composite shows a more comprehensive adaptability range of pH = 3–11 compared with many Fe-based amorphous catalysts. During kinetic analyses, the decolorization rates fitted well with both the pseudo-first-order reduction and pseudo-second-order adsorption models, implying that the removal of Orange II by porous Feam/Cu bimetallic composite involves both adsorption and catalytic modes of reduction. The strategy using the chemical replacement copper plating method to obtain porous Feam/Cu bimetallic composite is simple, cost-effective, and environmentally benign, making the large-scale production of porous Feam/Cu bimetallic composite possible for field remediation.

Enhancement of the photoelectrocatalytic degradation rate of a pollutant in the presence of a supercapacitor

Biochar was obtained by pyrolysis of spent malt rootlets and further treated with potassium hydroxide at 850 °C. The specific surface area of this biochar reached 1148 m2g-1, while the specific surface area of the micropores became 690 m2g-1. This biochar was used to make a supercapacitor electrode by depositing biochar particles on a carbon cloth and by immerging the electrode in a sodium sulfate aqueous electrolyte. The supercapacitance under the present conditions was 85 Fg-1. This electrode was introduced as a third electrode in a photoelectrochemical cell based on a semiconductor photoanode. A visible-light absorbing photocatalyst was obtained by combining titania with cadmium sulfide. Methylene blue was used as a model pollutant in order to study its photoelectrocatalytic degradation in the presence of the biochar. An impressive increase of the rate of dye removal from the aqueous solution has been observed, resulting to 60% increase under continuous illumination and 300% increase under intermittent light supply. This is attributed to the dual property of the biochar to act as strong adsorber of the dye and as a supercapacitor.

Synthesis of silver nanoparticles from microalgae for potential photocatalytic dye removal

Silver nanoparticles (AgNPs) with excellent optical and electronic properties is gaining significant attention by researchers for wastewater treatment. In recent years, the production of AgNPs has shifted towards green synthesis approach by using bio-reducing agent (e.g. plant extract). In this study, live cells Chlorella vulgaris were used as the bio-reducing agent to produce AgNPs from precursor (silver nitrate (AgNO3) solution). Two process parameters were investigated, namely incubation time and pH. The results affirmed that the optimum synthesis condition of AgNPs was at 24 hr incubation time and pH 8.4 in the mixture of live cells microalgae and 3 mM AgNO3 (3:1 v/v). The synthesized AgNPs showed Localized Surface Plasmon Resonance (LSPR) peak at 412.5 nm with absorption maxima of 0.81 a.u. as indicated using UV-Vis spectrophotometer. The synthesized AgNPs had shown 80.7% of photocatalytic dye degradation in 5 mg/L MB solution and 32.1% in 25 mg/L MB solution within 9 hr of incubation time. The dye removal rate with the addition of AgNPs was 1.2 times faster in 5 mg/L MB solution and was 3.5 times faster in 25 mg/L MB solution as compared to control set.

Application of QSAR for investigation on coagulation mechanisms of textile wastewater.

Coagulation is an effective preliminary treatment process for textile wastewater. In order to evaluate the effectiveness of the coagulation process, we performed quantitative structure activity relationship (QSAR) analyses with total organic carbon (TOC) removal rates (Rexp) as an index by three different coagulants (AlCl3, FeCl3, and MgCl2). The experimental results showed that the average Rexp of the three coagulants was 39.12%±2.60%, 51.60%±2.88%, and 49.95%±3.17%. Subsequently, 42 molecular descriptors of dye molecules were calculated by quantitative calculation softwares Gaussian 09, Material Studio 7.0, and Multiwfn 3.7, and then QSAR models were constructed by a multiple linear regression (MLR) method for the three coagulation systems. The developed QSAR models demonstrated excellent stability, robustness, and predictability with values of R2 =0.7677, 0.8015, and 0.7035, Q2INT =0.6067, 0.7026, and 0.5898, Q2EXT =0.5505, 0.5076, and 0.5697, respectively. Based on the analysis of quantum parameters, the coagulation mechanism for AlCl3, FeCl3 is primarily electrostatic adsorption as well as hydrogen bonding, while MgCl2 coagulates dyes mainly by electrostatic adsorption. This study provides an assessment of the removal rules and a feasible method for predicting dye removal rates in AlCl3, FeCl3, and MgCl2 coagulation process.

Fabrication of electrospun polyamide–weathered basalt nano-composite as a non-conventional membrane for basic and acid dye removal

In this study, an adsorptive electrospun polyamide membrane (ESPA) and electrospun polyamide–weathered basalt composite membrane (ESPA-WB) were prepared by an electrospinning process at room temperature. Hence, the WB structure was built as a polymeric membrane separation film in combination with the ESPA matrix as a composite nano-filtration membrane. Then, the ESPA and ESPA-WB membranes were characterized using BET surface area analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy (SEM). To avoid cracks forming during the sintering process, the WB should be added in certain percentages. The microstructures of the prepared membranes were investigated to evaluate their efficiency for basic and acidic dyesʼ removal and their permeation flux. Compared with the ESPA, the ESPA-WB membrane combines the characteristics of WB and ESPA, which greatly enhances the performance of both methylene blue (MB) and methyl orange (MO) dyes removal from synthetic wastewater. The outcomes of this study indicated that the dye uptake in the case of ESPA-WB is higher than that of ESPA, and it decreases with an increase in dye concentrations. The obtained membrane ESPA-WB showed both an excellent anti-dye fouling and a good rejection property for both dyes (i.e. 90% rejection for MB and 74% for MO) with no sign of contamination by the applied dyes. It was found that the structure of the ESPA-WB membrane contains a large number of several adsorption sites which leads to an increase in the removal rate of dyes. Hence, this study demonstrated a non-conventional strategy to prepare an effective adsorptive nano-composite membrane that can be applied as a highly recyclable one for the removal of organic dyes.Graphic abstract

Adsorption properties of methylene blue and gentian violet of sodium vanadate nanowire arrays synthesized by hydrothermal method

In the present study, the facile hydrothermal method is used to prepare sodium vanadate (Na5V12O32) nanowire arrays to act as adsorbents for removing cationic dyes. The samples are characterized and compared using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrum, and X-ray diffraction. The adsorption quantity of methylene blue and gentian violet increases with the increase of adsorbent dose, adsorption time and initial dye concentration. Further, the adsorption kinetic and isotherm are well modeled by the Pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The rate control step is administered by means of intra-particle diffusion during the adsorption process. The maximum adsorption capacities of methylene blue and gentian violet are 1249.0 and 1079.7 mg g−1, respectively. Additionally, the maximum dye removal rates for MB and GV are 85.32 % and 84.46 % after five cycles, respectively. As such, Na5V12O32 nanowire arrays can be used as an efficient, low-cost and recyclable adsorbent for cationic dyes removed from wastewater.

Efficient photodegradation of E124 dye using two-dimensional Zn-Co LDH: Kinetic and thermodynamic studies

Under mild conditions with a cation ratio of 1:1, Zn-Co layered double hydroxide (LDH) nanosheets were synthesized by co-precipitation. The effect of temperature on the physicochemical properties of LDH at 80, 300, and 500 ∘C was studied using x-ray diffraction (XRD), BET surface area, High resolution-Transmission electron microscopy (HR-TEM), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray Analysis (EDX), x-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), optical properties, and electron spin resonance (ESR) techniques. The FE-SEM confirmed that the formed Zn-Co LDH was cubically stacked up to thickness of 55 nm. HR-TEM shows that the interspacing between the layers was in the range of 1.95-2.70 nm and that the size slightly increased with temperature. Ponceau 4R (E124) was removed more efficiently than the Tartrazine (E102) dye from water using LDH-300. Different parameters that affect the photo-degradation process were performed, as: different calcination temperatures, initial dye concentration, LDH dosage, pH, and reaction temperature. The Photocatalytic degradation and adsorption processes showed dye removal of 90 and 80%, respectively. The highest degradation rate of E124 dye removal has been achieved using LDH-300. The kinetic parameters of the degradation process indicate that the kinetic data fits with the first-order kinetic reaction. The activation energy was found to be 18.189 KJ/mol. Thermodynamic parameters showed that the photodegradation process was non-spontaneous and endothermic. The adsorption coefficient was found to be 0.002961. Surface properties, FTIR, XPS, and FESEM were studied after the photodegradation process. The total free radicals were calculated by ESR analysis.

The Adsorptive Removal of Bengal Rose by Artichoke Leaves: Optimization by Full Factorials Design

Currently, the dye industry is increasing its production as a consequence of the growing need for their products in different manufacturing sectors, such as textiles, plastics, food, paper, etc... Thereafter, these industries generate very large volumes of effluents contaminated by these dyes, which require proper removal treatment before final discharge of the effluents into the environment. In this study, artichoke leaves were used as an economical and eco-friendly bio-adsorbent for Bengal Rose (BR) dye removal. Bio-adsorbent obtained from artichoke leaves was ground to powder size. The resulting powder was characterized by different methods, such as Brunauer-Emmett-Teller (BET) surface area analysis, scanning electron microscopy(SEM), X-ray Diffraction (XRD), Fourier transfer infrared (FTIR), pH at point of zero charge (pHpzc), equilibrium pH, iodine number, methylene blue number, phenol number, density, Energy dispersive X-ray spectroscopy (EDX) and Thermo-gravimetric analysis (TGA). Thereafter, the bio-adsorbent was used to study its capability for removing BR dye by testing contact time, initial concentration of dye and temperature. The results show that the saturation of bio-sorbent was reached after 40 min and the removal rate of BR dye by artichoke leaves powder (ALP) was 4.07 mg/g, which corresponds to a removal efficiency of 80.1%. A design of experiences (DOE) based on a two-level full factorial design (23) was used to study the effects of different parameters, such as pH, temperature and bio-adsorbent dosage on BR dye removal efficiency. The obtained results show that the highest removal efficiency was 86.5% for the optimized values of pH (4), temperature (80 °C) and bio-adsorbent dosage (8 g/L). Furthermore, a satisfying accordance between experimental and predicted data was observed. The kinetic and isotherm studies show that the pseudo-second order model simulated adequately the obtained data and it was found that Langmuir and Temkin isotherm models are liable and suitable for evaluating the adsorption process performance. Free energy change of adsorption (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°) were furthermore calculated to predict the nature of the adsorption process.

Removal of methylene blue (basic dye) by coagulation-flocculation with biomaterials (bentonite and Opuntia ficus indica)

The use of conventional chemical coagulants and flocculants to treat pollutant-laden effluents generates residues with harmful effects on the environment. This has led us to think through this study of their replacement by more ecological natural products. The present work focuses on the use of a bentonite-based coagulant and a cactus-based flocculant (Opuntia ficus indica (OFIP)) in the elimination of a methylene blue (MB), a basic textile dye. The biomaterials are characterized by FTIR, XRD, SEM and pHPZC. To estimate the performance of the biomaterials in the coagulation-flocculation process, jar-test work was performed on the MB dye in aqueous solution. The monitoring of the variation of MB removal rates was performed by UV–visible spectroscopy. The effect of biomaterial masses, stirring time and speed and settling time on the dye removal process were studied. In addition, the effects of pH and initial MB concentration were also studied. The results show that a mass of 0.9 g of bentonite and 0.4 g of OFIP are the optimal quantities, giving a dye removal rate of 98.29 % during 19 min, at a stirring speed of 180 rpm and 40 rpm for coagulation and flocculation, respectively. These optimum values are obtained with a settling time of 15 min. However, pH does not have a significant influence on the MB removal rates. These biomaterials gave excellent results with 98.99 % dye removal rates at an initial MB concentration of 90 mg/L. In addition, for the purpose of testing the performance of the biomaterials, a comparative study using conventional chemicals was performed.

QSAR model and mechanism research on color removal efficiency of dying wastewater by FeCl3 coagulation

Coagulation is the most widely used method in the treatment of printing and dying wastewater. To better understand the relationship between the coagulation effect and dye molecular structures, quantitative structure activity relationship (QSAR) analyses were performed to elucidate the factors affecting the coagulation in ferric chloride (FeCl3) coagulation process. First, the coagulation experiments on 38 dye molecules were conducted to determine their color removal rates (Rexp) by FeCl3 under different pH conditions (i.e., pH = 4 and 10). The results showed that the average Rexp of dyes were 41.36% ± 2.40% at pH value of 4 and 55.70% ± 2.83% at pH value of 10. Subsequently, a multiple linear regression (MLR) method was used to construct QSAR models based on Rexp and 42 molecular parameters calculated by Gaussian 09, Materials Studio 7.0 and Multiwfn. The developed QSAR models exhibited excellent stability, reliability, and robustness with values of R2 = 0.7950, 0.8170, Q2INT = 0.6401, 0.7382, Q2EXT = 0.5168, 0.5441, at pH values of 4 and 10, respectively. Through analysis of quantum parameter values, electrostatic adsorption and hydrogen bonding adsorption were primarily responsible for the coagulation process. Therefore, this study could be useful in providing critical information for evaluating the removal efficiency and a feasible way to predict the removal rate of dyes by FeCl3 when no coagulation experiments were conducted.

Biosorption of malachite green dye over Spirulina platensis mass: process modeling, factors optimization, kinetic, and isotherm studies

Spirulina platensis is one of the types of blue-green algae that was used as a biosorbent in this study. The aim of this study was to investigate the efficiency of S. platensis in removing MG from aqueous solutions and also to evaluate the biosorbent capacity using different kinetic models and isotherms. To obtain the optimum condition for MG biosorption using BBD, input factors included the initial level of MG 20–200 mg.L−1), dose of S. platensis (0.1–1.5 g.L−1), pH (4–9), and contaact time (5–80 min). The statistical method of BBD was considered to evaluate the removal rate of MG dye from aqueous solutions. The prediction of MG removal efficiencies and the evaluation of variable interactions were performed using a polynomial equation. The maximum removal efficiency of MG was obtained as 94.12% under MG level of 100.54 mg. L−1, pH of 7.57, contact time of 52.43 min, and S. platensis dose of 0.98 g. L−1. The removal MG efficiency enhanced with the increase in pH, reaction time, and S. platensis dose, and reduced with the decrease in MG level. The quadratic model suggested that the pH had a high impact on MG removal. The isotherms and kinetics data could be properly illustrated by the Freundlich model and the pseudo-second-order equation. Thermodynamic factors, including ΔG0, ΔH0, and ΔS0 showed the adsorption of MG onto S. platensis was spontaneous and exothermic. The acquired findings also showed that the physisorption mechanism mainly govern the MG sorption process. As a result, S. platensis showed excellent adsorptive properties and hence could be offered as a viable option for eliminating MG from aqueous solutions.

Novel PVC-melamine mixed matrix membranes for the Sirius Red removal from aqueous solutions: Experimental study and RSM modeling

In this paper, ultrafiltration polyvinyl chloride (PVC) mixed matrix membranes (MMMs) containing melamine were synthesized via the phase separation procedure in order to remove Sirius Red (SR) dye from the aqueous solution. The amount of melamine loading in the membrane structure was 1, 3, and 5 wt%. The fabricated MMMs were characterized by Fourier transform infrared (FTIR), Field emission scanning electron microscopy (FESEM), water contact angle, and mechanical resistance tests. Other specifications such as porosity, mean pore size and pure water flux of MMMs were also investigated. The obtained pure water flux data showed an increase up to 180 L/m2h for the PVC membrane containing 3 wt% of melamine (PVC-G-Mel3) and then decreased due to the agglomeration of melamine particles. Next, the rate of dye removal by MMMs at different pH values and feed concentrations was evaluated during the filtration time of 24 h. The ultrafiltration results were modeled by Design Expert 12 software to study the interaction of these parameters on SR removal as well as the effect of each independent factor. The dye removal efficiency gradually decreased with an increase in the feed concentration, while exhibiting a peak as pH increased from 2 to 8. The outcomes revealed that the highest dye removal efficiency of 95.65% was obtained at pH 5 and the color concentration of 30 ppm. Furthermore, the PVC-G-Mel3 MMM was regenerated by washing with 0.01 M hydrochloric acid solution for a few minutes and then cleaning with deionized water for 2 h before the next cycle. The flux recovery at 30 ppm feed concentration after three regeneration cycles was 95.44%, which showed that the synthesized MMMs can be a good candidate for removing SR dye from aqueous solution.

Environmentally Friendly g-C3N4/Sepiolite Fiber for Enhanced Degradation of Dye under Visible Light.

Herein, novel visible light active graphitic carbon nitride (g-C3N4)/sepiolite fiber (CN/SS) composites were fabricated via a facile calcination route, exploiting melamine and thiourea as precursors, and sepiolite fiber as support, for efficient degradation of organic dye methylene blue (MB). The as-prepared CN/SS composites were characterized by various characterization techniques based on structural and microstructural analyses. The effects of CN loading amount, catalyst dosage and initial concentration of dye on the removal rate of dye under visible light were systematically studied. The removal rate of MB was as high as 99.5%, 99.6% and 99.6% over the composites when the CN loading amount, catalyst dosage and initial concentration of dye were 20% (mass percent), 0.1 g, and 15 mg/L in 120 min, respectively. The active species scavenging experiments and electron paramagnetic resonance (EPR) measurement indicated that the holes (h+), hydroxyl radical (·OH) and superoxide radicals (·O2−) were the main active species. This study provides for the design of low-cost, environmentally friendly and highly efficient catalysts for the removal of organic dye.

From mining waste to environmetal remediation: a nanoadsorbent from Amazon bauxite tailings for the removal of erythrosine B dye

In this study, bauxite washing residues (i.e. mining tailings) from the Brazilian Amazon region were explored as low-cost precursor for the preparation of a pyroaurite-like (Mg-Fe-Al-NO3) layered double hydroxides (LDH) nanonoadsorbent. The synthesis was predicated on a simple co-precipitation approach in order to achieve a “low-end” adsorbing nanomaterial amenable to environmental remediation. The nanoadsorbent was structurally and morphologically characterized by X-ray diffraction (XRD), infrared (FTIR) and Raman spectroscopy, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and specific surface area measurements (BET method). The material was tested for erythrosine B removal from aqueous solutions. Effect of temperature, pH, contact time and initial dye concentration on the nanoadsorbent performances were also investigated. The LDH proved to be suitable for fast and efficient removal of erythrosine B. Indeed, almost complete dye adsorption on the nanostructured pyroaurite occurred in the first 20 min leading to an adsorption capacity (qe) equal to 94.25 mg/g for a specific surface area of 81 m2/g. Kinetic experiments data were fitted with a pseudo-second order model resulting into R2 equal to 0.995, whereas calculated qe values (depending on the initial dye concentration) were very close to the experimental ones. Coefficients associated to Langmuir, Freundlich and Temkin isotherm models (RL, n, and KT, respectively) revealed a strong interaction (i.e. affinity) between the dye and the nanadsorbent allowing high amounts of erythrosine B to be retained on the LDH. Non-linear fits were found to describe more accurately the adsorption process than the corresponding linear regression procedures for every and each isotherm. Based on thermodynamic parameters, the adsorption process turned out to be spontaneous and endothermic in nature. As for temperature effects, dye removal rate (percentage) increased from 89% to 93% as the temperature was raised from 35 °C to 55 °C.

Improved stability and promoted activity of laccase by One-Pot encapsulation with Cu (PABA) nanoarchitectonics and its application for removal of Azo dyes

Immobilization of laccase helps protect the laccase and realizes repeated use. However, excessive encapsulation protection will also limit the release of laccase activity. This work introduces an effective one-pot method encapsulating laccase in the porous material of metal organic framework (MOF) containing specific metal ions, which provided a new way to solve the problem of limited laccase activity. The immobilization process was mathematically modeled. The morphological and encapsulated properties of the prepared materials were confirmed by the characterization results of SEM, FTIR, XRD, TGA, XPS and CLSM. The results showed that laccase was successfully encapsulated, and the Cu (PABA) with Cu2+ as the central structure promoted the laccase activity, the activity of immobilized laccase increased by 1.7 times. The prepared laccase@Cu (PABA) (Lac@Cu (PABA)) showed enhanced stability to extreme pH, high temperature and storage time. More importantly, the Lac@Cu (PABA) exhibited superior reusability, maintaining 70% removal rate of Direct Red 31 (DR31) even after 10 cycles. The dye removal rate of immobilized laccase reached 92% in 6 h under optimal conditions. This research improved the stability of laccase while releasing the activity of laccase, which not only broadened the applicable environment of laccase, but also increased the rate of degradation, and provided a new idea for the clean and efficient treatment of water pollution in textile industry.

Novel Poly(ester amide) Membranes with Tunable Crosslinked Structures for Nanofiltration.

Tuning the crosslinking density of interfacial-polymerized nanofiltration (NF) membranes varying from loose to dense structures can make them meet the demand of various applications. The properties (e.g., pore size and porosity) of NF membranes can be tuned by choosing monomers with different structures and reactivities. Herein, tris(hydroxymethyl)aminomethane (THAM), a low-cost and green monomer, is first employed for the preparation of poly(ester amide) (PEA) thin-film composite membranes via interfacial polymerization. The moderate reactivity of THAM enables rational regulation of the crosslinking density of PEA membranes from loose to dense structures by varying the THAM concentration, which can hardly be achieved for traditional polyamide or polyester membranes. The developed PEA membranes with a wide tunability range of crosslinking densities broaden their potential utility in NF. PEA membranes with dense structures show exceptional desalination performance with a water permeance of 11.1 L m-2 h-1 bar-1 and a Na2SO4 rejection of 97.1%. However, loose PEA membranes exhibit good dye/salt separation performance with a dye removal rate over 95.0% and negligible NaCl rejection (<7.5%), as well as high water permeance (>45 L m-2 h-1 bar-1). This work implies that PEA membranes with tunable crosslinked structures provide new possibilities for the development of task-specific separation membranes.

Adsorptive removal of synthetic plastic components bisphenol-A and solvent black-3 dye from single and binary solutions using pristine pinecone biochar

The existing study deals with adsorptive removal of the endocrine-disrupting chemical bisphenol-A and toxic azo dye solvent black-3 from single and binary solutions. These two chemicals are commonly used as an additive in the synthetic plastic industries. Among the tested twenty pristine and modified biochars, the pristine pinecone biochar produced at 750 °C revealed greater bisphenol-A removal. Simulation of the experimental data obtained for bisphenol-A and dye removal from the single-component solution offered a best-fit to Elovich (R2 > 0.98) and pseudo-second-order (R2 > 0.99) kinetic models, respectively. Whereas for the bisphenol-A + dye removal from binary solution, the values for bisphenol-A adsorption were best suited to Elovich (R2 > 0.98), while pseudo-second-order (R2 > 0.99) for dye removal. Similarly, the two-compartment model also demonstrated better values (R2 > 0.92) for bisphenol-A and dye removal from single and binary solutions with greater Ffast values (except for bisphenol-A in binary solution). The Langmuir isotherm model demonstrated the highest regression coefficient values (R2 > 0.99) for bisphenol-A and dye removal with the highest adsorption capacity of 38.387 mg g−1 and 346.856 mg g−1, correspondingly. Besides, the co-existence of humic acid revealed a positive impact on bisphenol-A removal, while the dye removal rate was slightly hindered in presence of humic acid. The absorption process showed monolayer coverage of biochar surface with contaminants using a chemisorption mechanism with fast reactions between functional groups on the adsorbate and adsorbent. Whereas the adsorption mechanism was primarily controlled by hydrogen bonding, hydrophobic and π-π electron-donor-acceptor interactions as confirmed by FTIR, XPS, and pH investigations.