Dye Removal Capability Research Articles

Two-response surface design optimization of carboxylated CNCs with super high thermal stability and dye removal capability

Discharging wastewater from industrial dyeing and printing processes poses a significant environmental threat, necessitating green and efficient adsorbents. Cellulose nanocrystals (CNCs) have emerged as a promising option for dye adsorbing. However, the industrial production and commercialization of CNCs still faced low yield, time-consuming, and uneco-friendly. In this study, we proposed a facile hydrochloric/maleic acid (HCl/C4H4O4) hydrolysis method to synthesize carboxylated CNCs using Box-Behnken design and dual response surface design, which can systematically investigate the effect of experimental factors (temperature, time and HCl/C4H4O volume ratio) on the final products. The rod-liked carboxylated CNCs gave the highest yield of 90.50 %, maximum carboxyl content of 1.29 mmol/g, and efficient dye removal ratio of 91.5 %. Furthermore, compared to CNCs obtained by commonly sulfuric acid hydrolysis way (CNCs-S) with a Tmax of 242.6 °C, the CNCs extracted at 5 h exhibited significantly improved thermal stability with Tmax reaching 351.2 °C. The enriched carboxyl content and excellent thermal stability show potential wastewater treatment applications under harsh conditions.

CoFe2O4/PANI/MWCNTs ternary hybrid composites. Synthesis, characterization, the effect of MWCNTs ratio and dye removal capability.

We have synthesized cobalt ferrite (CoFe2O4) using the sucrose auto-combustion method and subsequently employed the in situ polymerization technique to fabricate ternary composites comprising CoFe2O4, polyaniline (PANI), and multi-walled carbon nanotubes (MWCNTs). In this novel investigation, we explored the influence of varying MWCNTs ratios on these composites' structural, magnetic, thermal, and electrical properties. The crystal structures of the synthesized composites were analyzed using X-ray diffraction (XRD), while Fourier transform infrared (FT-IR) spectroscopy revealed changes in bonding patterns, including the disappearance of ferrite bonds and the emergence of new ones. Transmission electron microscopy (TEM) images illustrated a complete coating of PANI on both MWCNTs and CoFe2O4 particles, resulting in a substantial reduction in magnetization compared to pure CoFe2O4 ferrite due to PANI's nonmagnetic nature. Vibrating sample magnetometer (VSM) measurements confirmed this reduction, indicating a decrease to 7.3 emu.g-1. Thermal analysis demonstrated an enhancement in thermal stability with increasing MWCNTs content, as evidenced by an increase in the temperature equivalent for half decomposition (T50) from 486 to 522°C for composites with 40% MWCNTs. Moreover, the electrical conductivity showed a corresponding rise with MWCNTs content, increasing from 3.1 × 10-3 Ω-1.cm-1 to 2.2 × 10-2 Ω-1.cm-1, possibly indicating charge transfer from PANI to MWCNTs. To assess practical applications, we investigated the ability of the composite with 40% MWCNTs to remove phenol red (PR) dye from aqueous solutions. Through a systematic study of adsorption parameters and kinetics, we determined optimal conditions for effective dye removal and elucidated the underlying adsorption mechanism. Our results demonstrated the composite's efficiency in dye removal, with a 6.4mg·g-1 capacity for PR dye, highlighting its potential for environmental remediation efforts.

Facile and Nondestructive Transformation of Intrinsic Hydrophobic Behavior of a Carbon Nanotubes Sheet to Hydrophilic.

It is imperative to induce hydrophilicity in intrinsically hydrophobic carbon nanotubes (CNTs) without losing their superior properties for applications that specifically deal with aqueous media. A method for transforming a CNTs sheet from hydrophobic to hydrophilic by treatment with N-methyl-2-pyrrolidone (NMP) is explored. The NMP-treated CNT sheets are assessed based on complementing characterization, and it is concluded that the binding of NMP to a CNTs surface is through noncovalent interaction without the incorporation of defects in CNTs. The induced hydrophilicity in the CNTs sheet is stable for water exposure over a longer duration while it displays a semireversible nature upon heat treatment. The mechanical and electrical properties of the NMP-treated CNTs sheet revealed enhancement in the tensile strength from 221 to 421 MPa while maintaining a good electrical conductivity of ∼1.22 × 104 S/m because of the improved interfacial properties. The hydrophilic CNTs exhibited excellent adsorption capacity for methylene blue dye. The NMP-treated CNTs sheets demonstrated their suitability in flexible hybrid supercapacitor (FHSC) devices with improved electrochemical performance with enhancement in the capacitance from 5.4 to 7.6 F/g and a decrease in the equivalent series resistance from 53 to 34 Ω compared to pristine CNTs-based devices. These solid-state FHSC devices displayed excellent cyclic charge-discharge performance along with robust behavior over thousands of bending cycles without significant performance degradation. The excellent dye removal capability and superior electrochemical performance of the NMP-treated CNTs sheet is a consequence of their improved interface with aqueous media, which is governed by the hydrophilic nature of the CNTs sheet.

Deep analysis of adsorption isotherm for rapid sorption of Acid Blue 93 and Reactive Red 195 on reactive graphene.

Graphene-based adsorbent was prepared by adopting a green synthetic route via the chemical exfoliation of graphite and low-temperature thermal activation. Prepared reactive graphene (RG) was characterized through various techniques, and its adsorption capabilities for textile dye removal were investigated for Acid Blue-93 (AB) and Reactive Red-195 (RR) under different operational conditions. The dye sorption equilibrium and mechanism were comprehensively studied using isotherm and kinetic models and compared statistically to explain the sorption behavior. Results show AB and RR adsorption by RG attains equilibrium in 60min and 70min, with a high sorption quantity of 397mgg-1 and 262mgg-1 (initial dye concentration of 100mg L-1), respectively. The dye sorption anticipates that the high surface area (104.52 m2 gm-1) and constructed meso-macroporous features of RG facilitated the interaction between the dye molecules and graphitic skeleton. The R-P isotherm fitted the best of equilibrium data, having the least variance in residuals for both dyes (AB = 0.00031 and RR = 0.00047). The pseudo-second order model best fitted the kinetics of sorption on RG, with chemisorption being the predominant process delimiting step. The overall results promise the dye removal capability of RG to be an efficient adsorbent for azo-based dyes from textile effluents.

Heterophase Grain Boundary‐Rich Superparamagnetic Iron Oxides/Carbon Composite for Cationic Crystal Violet and Anionic Congo Red Dye Removal

Iron oxide‐based nanostructures receive significant attention as efficient adsorbents for organic dye removal applications. Herein, iron oxide/carbon composite with well‐defined heterophase grain boundaries is synthesized by a simple precipitation method and followed by calcination. The local structure, spin dynamics, and magnetic properties of heterophase iron oxides/carbon composite are thoroughly investigated to explore its cationic and anionic dye removal capability. To validate the effectivity of the presence of heterogeneous grain boundaries, iron oxide/carbon nanocomposite with homogeneous grain boundaries is also examined. For an initial dye concentration of 50 mg L−1, pH 7, and adsorbent dose of 0.2 g L−1, the hetero‐IOCC exhibits a removal capacity of 71.63 and 140.19 mg g−1 for the cationic crystal violet and the anionic Congo red dyes, respectively. These values are significantly greater than those exhibited by as‐synthesized imidazole‐capped superparamagnetic α‐Fe2O3, 48.15 and 53.19 mg g−1; and homophase iron oxide/carbon nanocomposite, 12.51 and 17.95 mg g−1, respectively. Adsorption isotherms and kinetic studies indicate that the Langmuir isotherm model is found to be an appropriate model following the Elovich kinetic model. A detailed dye adsorption investigation on the pH effect, thermodynamic parameters, coexisting ionic effect, and reusability is also carried out.

Synthesis, Characterization and Dye Removal Capability of Conducting Polypyrrole/Mn0.8Zn0.2Fe2O4/Graphite Oxide Ternary Composites

Herein, ternary composites from polypyrrole (PPy), Mn0.8Zn0.2Fe2O4 (MZF), and graphite oxide (GO) were prepared to remove acid red dye (AR1) from wastewater. MZF was synthesized using spent Zn–C batteries, acid leaching, and sucrose auto-combustion processes; GO was prepared via oxidation and exfoliation of graphite. The composites were prepared by adding MZF and GO during the in-situ polymerization of pyrrole. Different PPy/MZF/GO (PMG) composites were prepared by changing the weight ratios of the PPy, MZF, and GO. We investigated the prepared composites’ structural, magnetic, and electrical/dielectric properties. We evaluated different experimental conditions’ influences on dye removal performance, such as pH, dosage, dye concentration, temperature, and contact time. XRD, FT-IR, and magnetic properties indicated that PPy completely coated the other contents. The electrical/dielectric properties improved while increasing the GO ratio. The PMG at GO content 50 wt.% (PMG50) showed the most efficient ratio for better removing AR1 from wastewater.

Performance evaluation of amino-functionalized mesoporous/PES nanofiltration membrane in anionic dye removal from aqueous solutions

In this study, the FSM-16 and FSM-16 modified by metformin (FSM-16-met) additives were applied as modifiers for polyethersulfone-based membranes. The modified membranes were evaluated in terms of morphology, surface roughness, hydrophilicity, pure water flux, pore size and porosity, and resistance ability. The obtained experimental data indicated promising enhancement in permeated flux and hydrophilicity after introducing the FSM-16-met nanomaterials into the membrane texture. In the case assessment of the fabricated membranes, dye removal capability was performed using the direct red-16 and methyl orange (30 mg/L). The modified membranes showed significantly higher dye rejection ability (> 97% for direct red-16 and 95% for methyl orange) compared to the bare membrane (76% for direct red-16 and 74% for methyl orange). The antifouling evaluations were run for milk powder (1000 mg/L) filtration and the best performance was obtained for the modified membrane with 0.1wt.% FSM-16-met (FRR = 95.55 ± 1.91%, Rir = 4.45 ± 0.089%). Also, the effect of the feed pH and concentration, temperature, and membrane driving force was considered on the membrane behavior. High stability in long-term performance was also observed for the modified membrane after 25 h re-running.

Incorporation of polyoxometalate in La-BTC metal-organic frameworks for fast and selective removal of methylene blue dyes in water

This study prepares Mo-doped, particulate La-BTC metal-organic frameworks (Mo/La-BTC MOFs) using polyoxometalate over a broad Mo atomic fraction (fMo) from 0 to 0.9, and examines their selective adsorption against methylene-blue (MB) dyes in water. An increased Mo concentration up to 0.61 ​at% results in the Mo/La-BTC MOFs when fMo was increased to 0.9. Raman spectroscopy reveals an enhanced MoO bond intensity. The Mo/La-BTC MOFs show a linearly dependent MB adsorption uptake with the increasing fMo; to which, the MOF particles remove up to 75% of MB in water within only 1 ​min when using an initial MB concentration of 5 ​× ​10−6 ​M. This is in significant contrast with virtually zero removal against methyl-orange dyes. Our results indicate that the selective dye-removal capability depends solely on the [PMo12O40]3- complex as active sites on the La-BTC scaffold, and the MB adsorption remains effective over a broad pH range (3–10).

Upcycling Glass Waste into Porous Microspheres for Wastewater Treatment Applications: Efficacy of Dye Removal

Each year about 7.6 million tons of waste glasses are landfilled without recycling, reclaiming or upcycling. Herein we have developed a solvent free upcycling method for recycled glass waste (RG) by remanufacturing it into porous recycled glass microspheres (PRGMs) with a view to explore removal of organic pollutants such as organic dyes. PRGMs were prepared via flame spheroidisation process and characterised using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and Mercury Intrusion Porosimetry (MIP) analysis. PRGMs exhibited 69% porosity with overall pore volume and pore area of 0.84 cm3/g and 8.6 cm2/g, respectively (from MIP) and a surface area of 8 m2/g. Acid red 88 (AR88) and Methylene blue (MB) were explored as a model source of pollutants. Results showed that removal of AR88 and MB by PRGMs was influenced by pH of the dye solution, PRGMs doses, and dye concentrations. From the batch process experiments, adsorption and coagulation processes were observed for AR88 dye whilst MB dye removal was attributed only to adsorption process. The maximum monolayer adsorption capacity (qe) recorded for AR88, and MB were 78 mg/g and 20 mg/g, respectively. XPS and FTIR studies further confirmed that the adsorption process was due to electrostatic interaction and hydrogen bond formation. Furthermore, dye removal capacity of the PRGMs was also investigated for column adsorption process experiments. Based on the Thomas model, the calculated adsorption capacities at flow rates of 2.2 mL/min and 0.5 mL/min were 250 mg/g and 231 mg/g, respectively which were much higher than the batch scale Langmuir monolayer adsorption capacity (qe) values. It is suggested that a synergistic effect of adsorption/coagulation followed by filtration processes was responsible for the higher adsorption capacities observed from the column adsorption studies. This study also demonstrated that PRGMs produced from recycled glass waste could directly be applied to the next cyclic experiment with similar dye removal capability. Thus, highlighting the circular economy scope of using waste inorganic materials for alternate applications such as pre-screening materials in wastewater treatment applications.

Enhanced antifouling and flux performances of a composite membrane via incorporating TiO2 functionalized with hydrophilic groups of L‐cysteine for nanofiltration

AbstractA new TiO2 nanoparticle modified via L‐cysteine is presented in this study. The L‐cysteine (cys) modified TiO2 nanomaterials impact as membrane modifier was examined in terms of pure water flux, hydrophilicity, morphology, and resistance ability. The mixed matrix membranes morphology investigated by using scanning electron microscope (SEM), atomic force microscopy (AFM), water contact angle measurement, porosity and pore size and Fourier transform infrared spectroscopy analysis. Membrane hydrophilicity and permeation flux were notably improved by introducing TiO2‐cys nanomaterials to the membrane matrix. The SEM image indicated the expanded finger‐like pores for the modified membranes comparing to the bare polyethersulfone (PES). The obtained AFM image exhibited lower surface roughness parameters for the modified membranes. In case of prepared membranes assessment, dye removal capability using the direct red‐16 and real liquorice wastewater were examined. The results confirmed that the modified membranes indicated high‐ranking dye rejection ability (more than 98% for direct red‐16 and 90% for real liquorice wastewater) comparing to the bare membrane (86 ± 2.58%). The antifouling tests were run based on milk powder (1000 mg/L) filtration and the best antifouling performance was obtained for 0.5 wt% of TiO2‐cys membrane (flux recovery ratio = 90.57 ± 2.71%, Rir = 9.43 ± 0.28%). Also, the results showed high potential of TiO2‐cys nanomaterials for membrane hydrophilicity enhancement.

3D porous bioadsorbents based on chitosan/alginate/cellulose nanofibers as efficient and recyclable adsorbents of anionic dye

Natural polysaccharides are attractive materials for fabrication of eco-friendly biodsorbents for efficient water remediation. However, scarcity of adsorbents that possess features of high stability and adsorption capacity at various pH conditions, low-cost, eco-friendly, and recycleability at the same time still remains a great challenge. Herein, porous ionically crosslinked biofoams were prepared by freeze-drying of chitosan (CS)/sodium alginate (SA) complex (CSA). FTIR and XRD were used to characterize the structure of the bioadsorbents. SEM observations revealed that adsorbents have a 3D interconnected porous structure, which is a favorable morphology for dye adsorption. Accordingly, CSA and its nanocomposite containing 15 wt% cellulose nanofibers (CSAC15) exhibited a fast and efficient adsorption behavior with qm values of 2015 and 2297 mg/g for adsorption of the Eriochrome black-T (EBT) anionic dye, respectively, which are quite outstanding among the developed EBT adsorbents in the literature so far. The CSAC15 preserved its stability and high adsorption capacity at various pH solutions. The adsorption of EBT onto the bioadsorbents was well-described with the pseudo-second order kinetics and Freundlich isotherm. The proposed CSAC15 bioadsorbent featured repeated dye removal capability after five cycles of adsorption.

Dual probes of Ag/Pd bimetallic NPs facilely synthesized by green process using Catharanthus leaf extract on textile dye removal and free radical capability

Silver–palladium (Ag/Pd) bimetallic nanoparticles were synthesized by greener way using Catharanthus leaf extract. The synthesized silver/palladium bimetallic nanoparticles were used to degrade the safranin O textile dye through photo catalytic activity and the free radical scavenging property was evaluated by DPPH assay test. Silver/Palladium bimetallic nanoparticles were synthesized by biogenic reduction method using silver nitrate and palladium chloride precursors assisted with CRL extract. The synthesized Ag/Pd bimetallic nanoparticles’ morphological and particle size were evaluated by the SEM/TEM image. The particle size was found to be within the nanoscale range of 15–30 nm. The 98% maximum dye degradation for 40 min time duration was achieved by the photocatalytic activity of silver/palladium bimetallic nanoparticles through UV light irradiation on safranin O textile dye and simultaneously antioxidant activity of silver/palladium bimetallic nanoparticles was also tested through DPPH assay test. The free radical scavenging efficiency was calculated for extract and extract with silver/palladium nanoparticles and was found to be 48.2% and 70.2%, respectively and revealed that the silver/palladium nanoparticles have 2.34 times higher scavenging activity when compared with Catharanthus leaf extract.

Investigation of Dye Removal Capability of Blast Furnace Slag in Wastewater Treatment

Blast Furnace Slag (BFS) is a by-product of the iron ore processing industry with potential to be used in different industrial applications. In this research, BFS was used to examine its ability for dye removal from wastewater. The efficiency of two types of BFS samples for removal of cationic methylene blue (MB) and acidic methyl orange (MO) dyes was investigated and results found that the optimal conditions for treatment of wastewater were 80 g/L of adsorbent dose and 1 h of treatment time for both dyes. BFS was found to be more effective for removal of the acidic MO dye than the cationic MB dye. Under shorter residence times, the results showed reverse trends with BFS samples removing higher concentrations of MB than MO. The BFS chemistry had additional impacts on the efficiency of dye removal. Higher basicity of BFS had lower dye removal ability for adsorption of acidic dye when applied at smaller concentrations, while for cationic dye when applied at higher concentrations. The results showed that BFS has potential role for pre-treatment of industrial wastewater contaminated with dyes and may contribute to reduced use of more expensive adsorbents, such as activated carbons.

Biosorption performance and cell surface properties of a fungal-based sorbent in azo dye removal coupled with textile wastewater

In this work, the biosorption ability of Sarocladium sp. dried biomass to remove Remazol Black dye has been studied. Optimum inoculum size and initial dye concentration were determined, and the salinity effect on the dye removal was evaluated. In the following, kinetic and isotherm of the adsorption were studied, and the adsorbent characteristics were determined using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, zeta potential, and Brunauer–Emmett–Teller analysis. Based on the results, maximum and minimum dye removal was determined at 1000 and 200 mg L−1 of Remazol Black dye as 54.39 and 24.02 mg g−1, respectively. Among the various azo dyes including Reactive yellow 145, Reactive blue 222, Reactive red 43, Direct blue 21, and Acid blue 161, dye removal capability of 87.96–97.43% was obtained. The solution salinity showed positive effect on the biosorption process. The biomass pretreatment with calcium nitrate enhanced the removal capacity by 70.48% and the maximum reduction in dye removal (− 61%) was obtained when the fungal biomass was treated by sodium hydroxide. Biosorption kinetic follows the first-pseudo-order model, and the obtained data best fits both Langmuir and Freundlich isotherm models. The maximum adsorption capacity of dried biomass for dye removal was 58.48 mg g−1. Based on FTIR, zeta potential value and pretreatment results, Yoshida H-binding, dipole–dipole H-binding, π–π and n–π interactions were probably involved in the dye adsorption process. The results showed that biomass has a high potential for different dyes adsorption from real textile wastewater. The present study declares the high potential of Sarocladium sp. dried biomass as an effective and inexpensive biosorbent which can be used for bio-treatment of effluents with multi-dyes.

Fabrication and characterization of a novel tannic acid coated boehmite/PES high performance antifouling NF membrane and application for licorice dye removal

We present a novel procedure for surface modification of boehmite nanoparticles via tanning-inspired coating. The impact of tannic acid coated boehmite (TA-BM) as a nanofiller on preparation of nanocomposite membranes were evaluated in terms of wettability, permeability, membrane morphology and fouling resistance capability. The surface morphology and chemical structure of TA-BM/PES blend membranes were investigated by SEM, AFM, measurement of contact angle and pore structure, FTIR and XRD analysis. Both of surface hydrophilicity and permeation flux of pure water improved significantly with incorporating of TA-BM nanofiller. The SEM image exhibited the wider finger-like pore of TA-BM/PES embedded membranes compared to bare PES membrane. The AFM image analysis indicated that, the roughness parameters of membranes reduced remarkably in presence of TA-BM nanostructures. In order to assessment of nanofiltration performance, the removal capability of Direct Red 16 and licorice dye was studied. The results revealed that, the TA-BM embedded membranes possessed superior dye removal capability (more than 96%) in comparison of bare membrane (90%). The antifouling performance tests of membranes studied by protein rejection. It was shown that, the best antifouling performance was belonged to 0.5 wt% TA-BM/PES blend membrane (FRR = 96.4%, Rir = 3.604). The TA-BM nanostructures had a great potential for surface treatment of hydrophobic membranes.

Development of nanofiltration PES membranes incorporated with hydrophilic para hydroxybenzoate alumoxane filler for high flux and antifouling property

The PES nanofiltration membranes incorporated with hydrophilic para hydroxybenzoate alumoxane (PHBA) filler were prepared with enhanced pure water flux, dye removal, and antifouling property. The fabricated membranes were characterized in terms of average pore radius, porosity, surface roughness, water contact angle, active layer thickness, and zeta potential. The surface roughness of the nanofiltration membranes decreased and the surface hydrophilicity of the nanofiltration membranes increased with the increase of the PHBA content. According to nanofiltration experiments, the highest pure water flux of the PES membranes incorporated with PHBA reached up to 80.47 kg/m2h under operation pressure of 0.4 MPa, which was nearly 5.8 times as much as that of the neat PES membrane. The PES membranes incorporated with PHBA filler also exhibited excellent antifouling performance and dye removal capability. In the best PHBA content with the P-PHBA 0.3 % membrane, the highest rejection of 99.21 and 98.53% were achieved for DR 16 and MB, respectively. Furthermore, the P-PHBA membranes exhibited good long-term operational pH stability for DR 16 rejection. P-PHBA 0.3 % membrane also exhibited the highest flux recovery ratio (98.50%) and the lowest irreversible fouling ration (1.50%). Moreover, the dominant fouling mechanism was determined using Hermia–"s model. This superior antifouling behavior and relatively high dye rejection combined with remarkable stability show the potential of the organic-inorganic fillers embedded nanofiltration membranes in sustainable water treatment technology.

Self-assembled hydrogels constructed via host-guest polymers with highly efficient dye removal capability for wastewater treatment

In this study, new self-assembled hydrogels constructed by cyclodextrin polymer (P-CD)/ferrocene-modified poly acrylic acid (PAA-Fc) were designed and prepared via host-guest interactions. These obtained hydrogels were characterized by different methods such as Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric (TG) and specific surface area tests. SEM images confirmed that the prepared hydrogels had a three-dimensional (3D) porous network structure with pore size ranging from several hundred nanometers to several tens of micrometers. The network structure of the hydrogels could be adjusted by varying the concentrations of P-CD. In addition, the gel-sol transition process would occur when the gel has redox stimulation. In particular, the prepared hydrogels have different adsorption mechanisms in the adsorption of poisonous organic molecules, including bisphenol A (BPA) and methylene blue (MB). It was found that the adsorption process had high pH dependence. The adsorption data for BPA and MB were found to be consistent with the pseudo-first-order model and the pseudo-second-order model, respectively. The maximum adsorption capacity of the hydrogel material reached 23.61 mg/g for BPA and 24.64 mg/g for MB. Present hydrogels removed BPA mainly via host-guest interaction and removed MB by hydrogen bonding and electrostatic interaction. Present obtained hydrogels provided new clues for the design of environmentally friendly hydrogel adsorbents.

Structural, Thermal, Magnetic and Electrical Properties of Polyaniline/CoFe2O4 Nano-composites with Special Reference to the Dye Removal Capability

CoFe2O4 nanoparticles were synthesized using environmentally friend sucrose auto-combustion method. PANI/CoFe2O4 nano-composites were prepared via in situ polymerization of aniline in the presence of various ferrite ratios. The structure, thermal, and electro-magnetic properties of the nano-composites were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), thermo-gravimetric analysis (TG), vibrating sample magnetometer (VSM), ac-conductivity and dielectric measurements. The structural properties exhibited the existence of the two phases and indicated core–shell structure. This core–shell was confirmed further through thermal and electrical properties measurements. The different PANI properties such as thermal stability, magnetic and the dielectric were obviously improved by ferrite incorporation whereas its conductivity remained unaffected. The nano-composites (10 and 30%) were investigated for the efficient removal of acid red dye (AR) from wastewater. In this category, the effect of various parameters including pH, contact time, temperature and mass on the removal capacity were investigated. The adsorption kinetics indicated that the adsorption followed the pseudo-second-order equation model through spontaneous endothermic adsorption process. The incorporation of ferrite within PANI increases the magnetic sensitivity of the nano-composite, which will facilitate the ease of separation of dispersed nano-composite from aqueous solutions using simple magnet after dye removing process. Generally, the moderate magnetic sensitivity, cost effective synthesis besides the acceptable obtained adsorption capability of the entire nano-composites could enhance their future use in the remediation applications.

Polyvinyl alcohol/carboxymethyl cellulose/ZSM-5 zeolite biocomposite membranes for dye adsorption applications

In this work, efficient biodegradable membranes were fabricated using polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) and ZSM-5 zeolite, and their utility for the removal of a cationic dye, methylene blue (MB), was investigated. The physical properties of the membranes were assessed by FTIR, XRD, UTM, SEM, optical microscopy and thermogravimetry. The influence of various parameters viz., zeolite loading, initial dye concentration, temperature and contact time on the dye removal capability of the membranes was investigated. The results show that the adsorption capacity of the membranes increases with an increase in zeolite content and initial dye concentration, while an elevated temperature decreases the adsorption capacity. A high dye removal efficiency (97%) and high adsorption capacity (7.83) were observed for 5 wt% of zeolite loaded sample for an initial dye concentration of 10 ppm with a contact time of 10 h at 30 °C. The equilibrium adsorption data were analysed using Langmuir and Freundlich models. The regression results showed that the equilibrium adsorption data were more accurately described by the Freundlich model (R2 = 0.998) rather than the Langmuir adsorption isotherm (R2 = 0.961), suggesting heterogeneous adsorption. The adsorption kinetic results show that the pseudo second order model (R2 = 0.996) is the suitable model to describe the kinetic behavior of MB onto PVA/CMC/ZSM-5 zeolite membranes.The present study suggests that the PVA/CMC/ZSM-5 zeolite membranes are suitable candidates for the efficient removal of methylene blue, from aqueous streams.

Beading of Co1-xZnxFe2O4 nanoparticles on MWCNTs. synthesis characterization, effect of Zn-substitution and dye removal capability

Multi-walled carbon nanotubes (MWCNTs) coated with magnetic Co1-xZnxFe2O4 nanoparticles (x = 0.0–1.0) were prepared via novel gelatin method. The synthesized nano-composites were characterized using X-ray diffraction, Fourier transform infrared (FT-IR) and transmission electron microscopy (TEM) to clarify the nano-composites formation and discuss the coating mechanism. The effect of the ferrite presence along with Zn-substitution on thermal stability, magnetic and conductivity characteristics was investigated and discussed. The addition of CoFe2O4 obviously decreases stability through catalyzing MWCNTs oxidative decomposition while increasing Zn-content inhibit it. The changes in the magnetization values by Zn addition was discussed in the view of changing cation distribution. All the investigated nano-composites exhibited metallic conduction characteristic of MWCNTs without any indication for any changes with Zn-substitution. The magnetic sensitivity along with high surface area exhibited by the entire nano-composites enhanced their use in adsorption removal of acid red (AR) toxic dye from aqueous solutions. In this category, the nano-composites with x = 0.0, 0.4 and 0.8 were examined to study the efficiency of the adsorption process and to investigate the effect of Zn-content on the adsorption. The effect of various parameters including pH, contact time, temperature and mass on the removal efficiency was also studied. In addition, the kinetic as well as the thermodynamic parameters were investigated and discussed.