A promising biosorbent for biosorption of a model hetero-bireactive dye from aqueous medium

In this study, residual shell biomass of Corylus avellana L. was used as potential biosorbent for biosorption of a model industrial hetero-bireactive dye. The biosorbent was characterized by FTIR and SEM. The batch biosorption studies were performed as a function of dye concentration and contact time. The biosorption of dye was found to be very quick. Various kinetic and isotherm models were used to evaluate the obtained experimental data. The biosorption kinetic was best represented by the pseudo-second-order model while the biosorption equilibrium was best described by Langmuir model. The maximum dye biosorption capacity of biosorbent based on Langmuir isotherm was obtained as 74.527 mg g^-1. These results showed that the use of such plant waste biomass in biosorption system could be a feasible method for the removal of such recalcitrant dye from industrial effluents to reduce operating costs.     

Sorption potential of modified nanocrystals for the removal of aromatic organic pollutant from aqueous solution

Chemically modified starch nanocrystals were used as adsorbents for the removal of aromatic organic compounds from water. The nanocrystals were chemically modified by grafting with stearate moieties which enhanced the adsorption capacity of the nanometric substrate. Their adsorption capacity ranged between 150 and 900 μmol g⁻¹ of modified nanoparticles and the adsorption isotherms could be described accurately by the Langmuir model. The adsorption kinetics followed a two-step process with first pure adsorption of the aromatic compounds onto the surface of the nanoparticles followed by a diffusion of the compounds into the layer of surface chains grafted onto the nanoparticles. Furthermore, the feasibility of using these nanoparticles in continuous flow mode processes was confirmed using a fixed bed column setup. The fixed bed column could also be regenerated by washing with ethanol and was found not to exhibit any loss in adsorption capacity over multiples adsorption-desorption cycles.     

Polyacrylamide grafted cellulose as an eco-friendly flocculant: Efficient removal of organic dye from aqueous solution

The efficient and safe flocculation of colored wastewaters from textile and leather industries is of great significance for natural environment and human health. In this work, an eco-friendly bamboo pulp cellulose grafting ployacrylamide (BPC-g-PAM) flocculant was synthesized and employed to remove organic dyes from dye solutions by flocculation. The flocculation performance of the synthesized BPC-g-PAM was evaluated by chroma and turbidity removals of a series of cationic and disperse dye solutions. A L₉(3⁴) orthogonal experiment was designed to optimize the flocculation process of the BPC-g-PAM. The positive results showed that, the BPC-g-PAM exhibited an excellent flocculation performance to organic dye solutions. The average decolorization rate reached 96.7 % and the chroma could be reduced to 5° or even lower for the disperse dye solutions. The mechanism of the BPC-g-PAM flocculation to disperse dyes was investigated and determined as chemical adsorption kinetics. Furthermore, the eco-friendly BPC-g-PAM also held an excellent biodegradability of 66.5 % at 45 d and 67.6 % at 90 d in soil extracting solution, which were far higher than the corresponding data of the commercial PAM.     

Use of 1,6-diaminohexane-functionalized glycidyl methacrylate-g-poly(ethylene terephthalate) fiber for removal of acidic dye from aqueous solution

In this study, removal of Congo red (CR) from aqueous solution by 1,6-diaminohexane-functionalized glycidyl methacrylate-g-poly(ethylene terephthalate) (HMDA-GMA-g-PET) fiber was investigated. A new aminated fibrous adsorbent was prepared by a reaction between amine and epoxy group in GMA-g-PET fiber prepared by grafting GMA monomer onto poly (ethylene terephthalate) (PET) fiber. Effects of various parameters such as pH, treatment time, initial, dye concentration, and reaction temperature on the adsorption amount of dye onto reactive fiber were investigated. The adsorption rates of CR were much higher on the HMDA-GMA-g-PET fiber than on GMA-g-PET and ungrafted PET fiber. The effective pH was 2.0 for adsorption on grafted PET fiber. It was found that the sufficient time to attain equilibrium was 60 min. The maximum adsorption capacity of the reactive fiber for CR is 16.6 mg/g fiber. The rates of adsorption were found to conform to the pseudo-second order kinetics with good correlation. It was found that the adsorption isotherm of CR fitted Freundlich type isotherm.     

Synthesis of urethane polycarboxylate as a novel adsorbent and its binary system dye removal ability from aqueous solution

In this paper, urethane polycarboxylate (UPC) as a novel adsorbent was synthesized and characterized. Dye removal ability of UPC from aqueous solution of single and binary systems was studied. Fourier transform infrared (FTIR) was used to characterize UPC. Basic Blue 41 (BB41), Basic Red 18 (BR18), and Basic Violet 16 (BV16) were used as cationic dyes. Dye removal isotherm and kinetic were evaluated. The effect of UPC dosage, initial dye concentration, and inorganic anions on dye removal was investigated. The capacity of UPC to remove BB41, BR18, and BV16 were 333 mg/g, 278 mg/g, and 222 mg/g, respectively. Dye removal kinetics and isotherm using UPC were fitted with the pseudo-second order and Langmuir model, respectively. The results showed the UPC might be used as a dye adsorbent to treat multicomponent systems containing cationic dyes.     

Modified polyamide 66 fibers for the removal of reactive dyes from aqueous suspension

In this paper, we report the modification of polyamide sample (PA) with different contents of chitosan (CS) using citric acid (CA) as a cross-linker [PA-CA-CS]. New materials were confirmed to be formed in PA using FT-IR spectrum. It is also checked in terms of the change in thermal stability event and decomposition behavior in thermogravimetry through TG-DTA instruments. Then, the ability of unmodified and modified supports was tested for the adsorption of two reactive dyes i.e. Cibacron Brilliant Yellow 3G-P and Cibacron Blue P-3R. Sorption experiments were performed under varying several experimental conditions such as pH, contact time, initial dye concentration, and temperature. The isotherm and kinetic models were undertaken to assess the dye removal mechanism. The applicability of Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin equations was checked and data were fitted using Langmuir model. The second-order equation was shown to fit the adsorption kinetics. Data gleaned from both thermodynamic results and modeling data indicate that the adsorption follows a chemical and exothermic process.     

Biosorption kinetics of Cu (II) ions removal from aqueous solution using bacteria

The present study highlights the effective removal of Cu (II) ions from synthetic solution using bacteria such as B. subtilis, P. aeruginosa and E. cloacae. Batch biosorption studies show that the biosorption of B. subtilis is effective when the concentration ranges from 25-200 mg L(-1). Biomass dosage, pH and the initial metal ion concentration have a profound effect on the biosorption process and this is reported in this study. In order to understand the nature of the biosorption process, Langmuir and Freundlich isotherm models were applied. Pseudo first and second order models were used to study the biosorption kinetics. The results show that these bacterial strains are very much suitable for the removal of Cu (II) ions. Being cost effective and efficient in toxic metal ion removal, these bacteria can be used on a large scale.     

Synthesis of SBA-15/PAni mesoporous composite for adsorption of reactive dye from aqueous media: RBF and MLP networks predicting models

In this research, SBA-15/polyaniline mesoporous composite was synthesized, characterized, and applied for the adsorption of Reactive Orange 16 (RO 16) as a reactive dye from aqueous media. Fourier transform infra-red spectroscopy (FTIR), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray diffraction (XRD), thermo gravimetric analysis (TGA), and BET were used to examine the structural characteristics of the obtained adsorbent. The input parameters including pH, dosage, temperature, and contact time were investigated and optimized. The obtained optimized conditions are as follows: pH=2, time=60 min, and adsorbent dose=0.4 g/l. Moreover, predictive models based on MLP (Multi-Layer Perceptron) and RBF (Radial Basis Function) networks were presented to predict the adsorption amount according to the input parameters including pH, dosage, temperature, time, and dye concentration. Two criteria, namely, correlation coefficient (CC) and root mean square error (RMSE) are used between the observed and predicted amounts to validate the models. Comparison of the obtained results using these two models showed that the prediction based on the MLP network model is better than the RBF network.     

Removal of benzidine-based azo dye from aqueous solution using amide and amine-functionalized poly(ethylene terephthalate) fibers

In this study, amide and amine groups bound to poly(ethylene terephthalate) fibers are used to remove the colored toxic Congo red dye from aqueous solution. The effects of process variables like pH, contact time, graft yield, and initial dye concentration on the adsorption were investigated. The maximum adsorption of Congo red to amide and amine groups was observed at pH 3 and 5 respectively. Equilibrium was attained at approximately 60 min for the amine group. The adsorption capacity of amine group on the poly(ethylene terephthalate) fiber was 46.5 mg g⁻¹ at 25 °C, which was higher than that of the amide group on the poly(ethylene terephthalate) fiber. Desorption was done using 0.1 M NH₃, and recovery was measured at 58.2 %. The used adsorbent was regenerated and recycled six times. The results showed that the amine-functionalized fiber could be considered as potential adsorbents for removal of Congo red from aqueous solution.     

The removal of heavy metals in aqueous solution by hydroxyapatite/cellulose composite

Hydroxyapatite has an excellent ion-exchangeability and is expected to be used as an agent for the removal of heavy metal ions in wastewater. However, the pure hydroxyapatite is very difficult to use because it exists in the form of white powder. Thus, the pure hydroxyapatite was mixed with cellulose to utilize its ion-exchangeability. In this research, a method for dispersion of hydroxyapatite in cellulose matrix is described and its dispersion is observed with scanning electron microscopy. The removal ratios of some heavy metal ions with hydroxyapatite composite are examined with regard to reaction time and amount of hydroxyapatite composite. The ion-exchangeability of hydroxyapatite composite did not seem to be interfered by cellulose matrix during removing heavy metal ions.     

Preparation and use of amine-functionalized glycidyl methacrylate-g-poly(ethylene terephthalate) fibers for removal of chromium(VI) from aqueous solution

Poly(ethylene terephthalate) (PET) fibers were grafted with glycidyl methacrylate (GMA) using benzoyl peroxide as initiator. 1,6-diaminohexane (HMDA) was then covalently attached to this GMA grafted PET fibers. Variations of time, temperature, initiator and monomer concentrations were investigated. HMDA-GMA-g-PET fibers were used as a new sorbent for removal of Cr(VI) ions from aqueous solutions through batch adsorption method. Effects of various parameters such as pH, treatment time, and initial ions concentration on the adsorption amount of ions onto reactive fibers were investigated. The adsorption rates of Cr(VI) ions were much higher on the HMDA-GMA-g-PET fiber than on GMA-g-PET and ungrafted PET fiber. Within 60 min, at pH 3, Cr(VI) was removed by 98 % while the initial concentration of ions was at 25 mg/l and by 94 % at 400 mg/l. The Cr(VI) ions adsorbed were easily desorbed by treating with 1M KOH within 10 min.     

Physicochemical assessment and bioactive properties of condensed distillers solubles,a by-product from the sorghum bio-fuel industry

Large volumes of condensed distillers solubles (CDS) are generated as by-products, from the sorghum bioethanol industry. The objective was to assess the physico-chemical and bioactive properties of CDS. The unfractionated CDS showed the highest content of phenolic compounds (16 mg GAE/g), antioxidant (522 μM Trolox/g) and antimicrobial activity (MIC 1%(w/v) against Campylobacter spp.) compared to its extracts. The water and methanol extracts also showed high levels of phenolic compounds and antioxidant activity (11.6 and 9.2 mg GAE/g and 349 and 409 μM Trolox/g respectively), followed by ethanol and acetone extractions (7.5 and 6.6 mg GAE/g; 337 and 346 μM Trolox/g respectively). A positive correlation was revealed between total phenol and antioxidant activity. The main phenolic compounds found in the extracts were protocatechuic acid, 4-hydroxybenzoic acid, taxifolin, ferulic acid, cinnamic acid and p-coumaric acid. This study indicates the potential of using CDS as a functional ingredient for other food and feed applications.     

Preparation of electrospun affinity membrane and cross flow system for dynamic removal of anionic dye from colored wastewater

In this research, poly(vinyl alcohol) (PVA)/chitosan electrospun nanofibrous membrane (ENM) was prepared by electrospinning method in order to investigate its dye removal ability from colored wastewater. The morphology and average fiber diameter of the membranes were investigated by scanning electron microscopy (SEM), image analysis and atomic force microscopy (AFM). The chemical characterization was studied by Fourier transform infrared spectroscopy (FTIR). The permeability of the membranes was evaluated by measuring pure water flux (PWF). In order to investigate the performance of the prepared membranes they were used in the batch adsorption and membrane separation for dye removal from colored wastewater. The effect of pH, number of membranes and dye concentration on the dye removal ability of the ENM was investigated. Response surface methodology (RSM) was used to achieve multi-objective optimization and equations of adsorption capacity and breakthrough time regarding operating conditions. The results demonstrated the potential of using PVA/chitosan nanofiber membrane as a microfiltration (MF) membrane for dye removal. Moreover, the recoverability property of prepared membranes was noticeable.     

Sorption properties of iron impregnated activated carbon web for removal of methylene blue from aqueous media

In this study, impregnation of iron chloride was carried out on needle punched web of waste acrylic fibers, which was subsequently carbonized under layer of charcoal by physical activation in high temperature furnace to produce iron impregnated activated carbon (FeAC). For comparison purpose, one more sample of activated carbon (AC) was prepared without impregnation of iron chloride. Both the webs were carbonized at 1200 °C with no holding time, and characterization of BET surface area, SEM morphology, EDX elemental analysis, XRD crystalline structure was performed. The FeAC web was used as adsorbent for the removal of methylene blue from aqueous solution. The dye removal percentage was investigated at different experimental parameters like different dye concentrations, adsorbent dosage, stirring speed and different pH. The obtained results were analyzed using linear and non-linear forms of Langmuir and Freundlich isotherms and adsorption kinetics (i.e. pseudo first order and pseudo second order model).     

A study of reusing vinyl sulfone based reactive dye for dyeing cotton fiber

Reactive dye is a popular dye for dyeing cotton fiber due to its very good color fastness which is explained by the formation of covalent bond between dye and fiber. In this study, practicality of reuse of reactive dye by compensating for the hydrolyzed part of the dye solution is examined. A monofunctional dye (vinyl sulfone type) was used and it was found that dyeing cotton fiber with reused dyebath is possible. Since bifunctional dye can improve the chance of dye-fiber bond formation, vinyl sulfone based bifunctional reactive dyes were also selected in this study. Three types of bifunctional dyes were used and they basically share the same vinyl sulfone group; other reactive groups are monochlorotriazine, dichlorotriazine and vinyl sulfone. Such dyes were chosen in order to compare their respective efficiencies under the effect of one common reactive group. The aim of this study was to compare the effect of hydrolyzed and unhydrolyzed proportions of mono-and bifunctional reactive dyes on cotton fiber and study the possibility and efficiency of the two different reuse dyebath systems.     

A scanner based neural network technique for color matching of dyed cotton with reactive dye

Conventional theory for color matching is Kubelka-Munk, but it fails in some situations. New intelligent procedures such as neural networks could learn the behavior of a complex system and produce accurate prediction. This paper investigates the ability of MLP (multiple layer perceptron) neural network for color matching of cotton fabric. Three reactive dyes, namely Levafix Red CA, Levafix Yellow CA and Levafix Blue CA were used for experiments. The dyed samples were scanned and L * a * b * histogram were extracted. Different neural networks were trained and tested using L * a * b * histogram of fabric’s images and also L * a * b * values (D65, 10°) of fabrics. The results were encouraging. For neural networks including the L * a * b * histogram in input vector, colorants and their concentration were predicted with a mean square error (MSE) less than 10^?5 and an average value of color difference (CMC (1:2)) less than 1.5 for approximately 80 % of testing data.     

Removal of some cationic dyes from aqueous solution by acrylamide- or 2-hydroxyethyl methacrylate-based copolymeric hydrogels

In this study, anionic hydrogels were prepared using a crosslinker (N,N′-methylenebisacrylamide) through a free radical addition reaction in aqueous solutions of neutral acrylamide or 2-hydroxyethyl methacrylate monomer and anionic monomers, mesaconic acid or aconitic acid. Cationic dyes along with safranine (azine-), nile blue (oxazine-) and methylene blue (thiazine-) were selected as models of pollutants, and adsorption of these dyes onto the hydrogels was investigated. To examine the effect of concentration on adsorption, dye solutions prepared with a concentration range of 5–50 mg l^?1 and 0.1 g hydrogel at 25 °C were exposed to the hydrogels until equilibrium was established. Dye adsorption onto the hydrogels was found to be an L type Giles adsorption isotherm. Monolayer sorption capacity and adsorption constant values were calculated from the Langmuir plots. To calculate R_L values, a non-dimensional analysis was used and they were always found to be 0<R<1. In other words, the hydrogels were favorable for adsorption of these dyes. Aqueous solutions of dyes were observed to interact with hydrogels in the following order: oxazine > azine > thiazine. Furthermore, the higher the number of carboxyl groups in the hydrogel composition, the higher the adsorbed amount of substance.     

Synthesis of cross-linked graft copolymer from acrylic acid, poly(vinyl alcohol), and glutaraldhyde for extraction of lead ion from aqueous solution

A novel graft copolymer of acrylic acid onto poly(vinyl alcohol) has been synthesized and it is cross-linked by glutaraldehyde for the investigation of its efficiency in removing lead ion from aqueous solution. The chemical nature of the ion exchange resin has been elucidated with the help of chemical, spectral, and thermal analysis. Particle size, surface area, ion exchange capacity, optimum pH, time, and temperature for Pb(II) adsorption were determined. Metal ion adsorption kinetics, isotherms, and thermodynamics have been studied. A plausible mechanism for lead ion exchange has been suggested.     

A novel approach for estimating the relation betweenK/S value and dye uptake in reactive dyeing of cotton fabrics

This paper focuses on the application of a novel mathematical limit approach derived forK/S values in reactive dyeing of cotton fabrics. The relation obtained from Kubelka-Munk equation is used because the Kubelka-Munk equation is the basic relationship among fabric reflectance, fabric dye content and dyestuff characteristics. The limit approach derived in a former paper is applied to the laboratory dyeings and the dyeing behavior of some reactive dyes on cotton knitted fabric has been obtained. The results of the laboratory experiments are discussed using the new mathematical approach. When the actualK/S values obtained from the dyeings and the calculatedK/S values derived by the limit approach are considered independently, it is observed that the limit relation is valid for low dye concentration applications. When theK/S values are calculated taking theK/S value of the initial dyeing concentration (0.1 % owf) as the starting concentration by applying the result of the derived limit approach, the calculatedK/S values fit with the ones obtained in actual dyeings. It is concluded that the novel approach presented in the paper can be used in calculating theK/S values when the initial dyeings at low dye concentrations are carefully carried out.     

Selective removal of Pb(II) ions from aqueous solutions by acrylic acid/acrylamide comonomer grafted polypropylene fibers

Polypropylene-based chelating fibers grafted with acrylic acid and acrylamide side chains were simply synthesized, and subsequently employed as adsorbents for Pb(II) removal selectively from aqueous solutions. The assynthesized fibers were characterized by elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscope, and water contact angle. The adsorption results revealed that kinetics data were fitted by a pseudo-second order model (semi-saturation time 6.2 min), thereby suggesting chelating interaction to be the main mechanism during the adsorption process. The adsorption isotherm data fitted well with a Langmuir model. The thermodynamic study revealed the adsorption of Pb(II) as an exothermic spontaneous chemisorptive process. Coexisting Na(I), Mg(II), and Al(III) in solution showed negligible effects in the adsorption process. As confirmed by carboxyl amination, the carboxylate oxygen preferentially chelates coexisting Ca(II) over Pb(II), thereby leading to lower extents of Pb(II)-O chelate interaction. The spent fibers were effectively and repetitively (five cycles) regenerated while maintaining high performance upon treatment with 1 M hydrochloric acid solutions.