High adsorption of dyes by water hyacinth fixed on alginate

Pollution from synthetic dyes has emerged to be a significant environmental issue over the past few decades. This has mainly been triggered by the increasing global dye production, possible toxic effects, undesirable colour and high persistence in the environment. Biosorption, which involves dye removal from aqueous solution by passive linkage in live and dead biomass, has shown great potential in removing dyes from aquatic environments. Among aquatic macrophytes, water hyacinth, Eichhornia crassipes, has shown great potential as a biosorbent. In this work, we investigated the removal of two basic dyes, methylene blue and crystal violet, using E. crassipes immobilized on alginate. Results showed that the Langmuir model better described the equilibrium sorption data when compared to the Freundlich model. Optimum amounts of methylene blue and crystal violet dyes were adsorbed in the alkaline pH range (8–10), 8 % biomass dose, and the amount of dye removed increased with increasing initial dye concentration. The equilibrium monocomponent adsorption capacities for the dyes were 111.1 and 43.5 mg/g, while the binary adsorption capacities were 26.1 and 11.6 mg/g for methylene blue and crystal violet, respectively. To conclude, we show for the first time that E. crassipes fixed on alginate beads can uptake and adsorb methylene blue and crystal violet dyes very effectively in batch systems and show great potential for dye removal from aquatic environments.     

Adsorption in combination with ozonation for the treatment of textile waste water: a critical review

Intrusion of synthetic textile dyes in the ecosystem has been recognized as a serious issue worldwide. The effluents generated from textiles contain large amount of recalcitrant unfixed dyes which are regarded as emerging contaminants in the field of waste water study. Removal of various toxic dyes often includes diverse and complex set of physico-chemical, biological and advanced oxidation processes adopted for treatment. Adsorption in itself is a well-known technique utilized for treatment of textile effluents using a variety of adsorbents. In addition, ozonation deals with effective removal of dyes using high oxidising power of ozone. The review summarizes dye removal study by a combination of ozonation and adsorption methods. Also, to acquire an effective interpretation of this combined approach of treating wastewater, a thorough study has been made which is deliberated here. Results assert that, with the combined ability of ozone and a catalyst/adsorbent, there is high possibility of total elimination of dyes from waste water. Several synthetically prepared materials have been used along with few natural materials during the combined treatment. However, considering practical applicability, some areas were identified during the study where work needs to be done for effective implementation of the combined treatment.

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Polyurethane for removal of organic dyes from textile wastewater

Synthetic organic dyes are extensively used in consumer products from textile to pharmaceuticals. A large amount of organic dyes is ultimately discharged as effluent into water bodies, thus posing a serious threat to environment and life. Therefore, removal of dyes from water bodies is needed. To address this problem, various synthetic and natural materials have been used to adsorb dyes. Here, we review the application of polyurethane for removal of organic dyes. First, we review the application of simple and modified polyurethane as efficient and economic adsorbents for dyes. Secondly, we review the polyurethane-based membranes for separation and adsorption of various dyes. Thirdly, we describe polyurethane composites with improved efficiency of dyes removal. Finally, we review the bioremediation of dyes where polyurethane has been proven as an excellent inert support.     

Removal of congo red dye from water using carbon slurry waste

A cheaper adsorbent has been prepared from carbon slurry waste obtained from National Fertilizer Limited (NFL), Panipat and investigated for the removal of congo red, an anionic dye. Its adsorption on prepared carbonaceous adsorbent was studied as a function of contact time, concentration and temperature. The results have shown that carbonaceous adsorbent adsorbs dye to a sufficient extent (272 mg g^-1). A comparative study of adsorption results with those obtained on activated charcoal shows that the carbonaceous adsorbent is ~95% efficient as compared to activated charcoal. Thus, it can be fruitfully used for the removal of dyes from wastewaters.This work has been presented at the National Symposium on Biochemical Sciences: Health and Environmental Aspects (BSHEA—2003), Agra, India (2003).     

Removal of dyes from water using crosslinked aminomethane sulfonic acid based resin

A new polymeric resin with amino sulfonic acid pendant functions has been prepared for the extraction of acidic and basic dyes from water. Beaded polymer supports were prepared by suspension polymerization of vinyl benzyl chloride (0.9 mol) and ethylene glycol dimethacrylate (0.1 mol). The resulting copolymer beads were modified with amino methane sulfonic acid. The dye adsorption capacity of the resin was found as 0.16 g dye/g resin for ramazol black and 0.15 g dye/g resin for crystal violet. The pH depending measurements and dye sorption kinetics of the resin were also investigated.     

Mutagenicity assessment of textile dyes from Sanganer (Rajasthan)

Sanganer town, district Jaipur (Rajasthan, India) is famous worldwide for its hand block dyeing and textile printing industries. These industries use a variety of chemicals and dyes during processing and finishing of raw materials. Most of the textile dyes used by these industries have not been evaluated for their impact on health and the environment. The workers in these industries are exposed to such dyes with no control over the length and frequency of exposure. Further, untreated and sometimes even treated effluents from these industries are released into surface waters of Amani Shah drainage or through the drainage systems, seep into the ground water and adjoining water bodies. Since many textile dyes are known carcinogens and mutagens, a complete evaluation of the safety of these dyes in the human environment must include an evaluation of their genotoxicity or mutagenicity. A total of 12 textile dyes from Sanganer were tested for their mutagenicity, by Ames Salmonella reversion assay using strain TA 100 of Salmonella typhimurium. Only 1 dye, Red 12 B showed absence of mutagenic activity. The remaining 11 dyes were all positively mutagenic.     

六方水钠锰矿对罗丹明B的去除效果及机理

六方水钠锰矿作为环境中一种具有较强氧化与吸附能力的氧化锰矿物,对环境中的有机染料有着一定的去除作用。采用常压回流法一步合成纳米六方水钠锰矿,运用X射线衍射(XRD)、电感耦合等离子体光谱仪(ICP-AES)、BET氮气吸附法、场发射扫描电镜(FESEM)和透射电镜(TEM)对其矿物晶体结构、化学组成、比表面积、孔径分布和微观形貌进行表征,选用罗丹明(RB)作为目标有机染料,研究反应条件对纳米六方水钠锰矿对RB的去除效果的影响(包括pH值、六方水钠锰矿浓度、染料浓度和温度)。进而研究六方水钠锰矿对RB的去除机制,通过在反应后的溶液中加入盐酸羟胺,使矿物溶解,吸附在矿物上的染料重新释放到溶液中,以区分吸附去除率和氧化去除率。结果表明,降低反应pH、增加六方水钠锰矿浓度、减小染料浓度以及提高温度均有利于六方水钠锰矿对罗丹明B(RB)的去除。其中影响最大的pH,反应体系pH为2.87时,RB的去除率达到99.9%,而pH为10.29时,RB的去除率仅为8.33%。通过去除机制实验结果表明,在pH为4.5时,RB的氧化去除率是36.3%,吸附去除率为4.6%,六方水钠锰矿去除RB以氧化去除为主。纳米六方水钠锰矿材料的重复利用效果很好,重复使用3次去除率,RB的去除率仅从90.6%降至85.9%。合成的纳米六方水钠锰矿有着很好的去除有机染料的效果,并且有一定的重复利用性,机制的研究也有利于提升对有机染料的去除效果。     

Effect of carbon and nitrogen source amendment on synthetic dyes decolourizing efficiency of white-rot fungus, Phanerochaete chrysosporium

Decolourization activity of Phanerochaete chrysosporium for three synthetic dyes viz., congo red, malachite green and crystal violet and impact of additional carbon and nitrogen supply on decolourization capacity of fungus were investigated. Maximum decolourizing capacity was observed up to 15 ppm. Addition of urea as nitrogen source and glucose as carbon source significantly enhanced decolourizing capacity (up to 87%) of fungus. In all the cases, both colour and COD were reduced more in non-sterilized treatments as compared to sterilized ones. Significant reductions in COD content of dye solutions (79-84%) were recorded by fungus supplied with additional carbon and nitrogen. A highly significant correlation (r = 0.78, p < 0.001) between colour and COD of dye solutions was recorded. Thus, a readily available carbon and nitrogen source is imperative to enhance the bioremediation activity of this fungus which has been the most suitable for synthetic dyes and textile industry wastewater treatment.     

Methods to prepare biosorbents and magnetic sorbents for water treatment: a review

Access to drinkable water is becoming more and more challenging due to worldwide pollution and the cost of water treatments. Water and wastewater treatment by adsorption on solid materials is usually cheap and effective in removing contaminants, yet classical adsorbents are not sustainable because they are derived from fossil fuels, and they can induce secondary pollution. Therefore, biological sorbents made of modern biomass are increasingly studied as promising alternatives. Indeed, such biosorbents utilize biological waste that would otherwise pollute water systems, and they promote the circular economy. Here we review biosorbents, magnetic sorbents, and other cost-effective sorbents with emphasis on preparation methods, adsorbents types, adsorption mechanisms, and regeneration of spent adsorbents. Biosorbents are prepared from a wide range of materials, including wood, bacteria, algae, herbaceous materials, agricultural waste, and animal waste. Commonly removed contaminants comprise dyes, heavy metals, radionuclides, pharmaceuticals, and personal care products. Preparation methods include coprecipitation, thermal decomposition, microwave irradiation, chemical reduction, micro-emulsion, and arc discharge. Adsorbents can be classified into activated carbon, biochar, lignocellulosic waste, clays, zeolites, peat, and humic soils. We detail adsorption isotherms and kinetics. Regeneration methods comprise thermal and chemical regeneration and supercritical fluid desorption. We also discuss exhausted adsorbent management and disposal. We found that agro-waste biosorbents can remove up to 68–100% of dyes, while wooden, herbaceous, bacterial, and marine-based biosorbents can remove up to 55–99% of heavy metals. Animal waste-based biosorbents can remove 1–99% of heavy metals. The average removal efficiency of modified biosorbents is around 90–95%, but some treatments, such as cross-linked beads, may negatively affect their efficiency.

     

Decolorization and degradation of acid dyes mediated by salt fractionated turnip ( Brassica rapa ) peroxidases

Peroxidases from turnip roots (524?U?g^?1 of vegetable) were highly effective in decolorizing acid dyes having wide spectrum chemical groups. Dye solutions, containing 40–170?mg?dye?L^?1, were treated by turnip peroxidases (TP) (specific activity of 122.0?U?mg^?1 proteins). These enzymes were able to decolorize most of the acid dyes in the presence of 2.0?mM 1-hydroxybenzotriazole (HOBT). Increasing concentration of enzyme and time in the absence of HOBT did not influence dye decolorization. The rate of decolorization was significantly enhanced when HOBT was added to the decolorizing solutions. The decolorization of all the used dyes was maximum at pH 5.0 and 40°C. Complex mixtures of dyes were significantly decolorized when treated with enzyme in the presence of HOBT (2.0?mM). Phytotoxicity test based on Allium cepa root growth inhibition has shown that majority of the TP-treated dye product were not more toxic than their parent dye. Kinetic parameters of the TP with various dyes showed that this enzyme has highest affinity for Acid Yellow 42. This study demonstrates that the peroxidase/mediator system was an effective biocatalyst for the treatment of industrial effluents from textile, dye manufacturing, dyeing and printing industries or complex mixtures of dyes.     

Modeling of adsorption kinetics and equilibria of acid dyes onto activated carbon in single- and binary-component systems

Adsorptive removal of Acid Blue 127 and Acid Yellow 17 from their single and binary solutions has been studied using powdered activated carbon (PAC). The dyes used extensively for dying of nylon fiber in textile industry are known as Nylomine Blue P-B (NB) and Nylomine Yellow P-4G (NY), respectively. Time-dependent results obtained from single-component system have been better predicted by two resistance diffusion model rather than homogeneous surface diffusion. The magnitudes of film- and intraparticle diffusion coefficients calculated from McKay equation are ～10^?9 and ～10^?15 m² s^?1, whereas surface diffusion coefficients have been estimated as ～10^?13 m² s^?1 using Vermeulen approximation. Experimental equilibrium isotherms have been evaluated by changing initial dye concentrations in the range of 0.02–1.00 of mmol L^?1. Freundlich isotherm parameters for individual solutions of the dyes have been used to predict their equilibrium behaviors in binary solutions by applying extended Freundlich model. Langmuir isotherm model and its extended form have also been fitted to the data for single- and binary-dye solutions, respectively. Thermodynamic functions derived from the temperature dependence of adsorption equilibrium constants in 298–318 K range show that adsorption processes are endothermic but spontaneous.     

改性活性氧化铝除磷性能的试验

为提高活性氧化铝对废水中磷的去除效果,以硫酸铝为改性剂,采用浸渍法对其进行改性;测定了改性前后活性氧化铝的比表面积及孔容孔径;考察了吸附时间、pH、废水初始浓度、改性剂投加量等因素对去除废水中磷的影响;探讨了改性活性氧化铝对磷的吸附机理.结果表明,改性后活性氧化铝的比表面积为398.364 m2/g,提高了14.22%...     

Natural dyes and antimicrobials for green treatment of textiles

Increasing studies on extraction, purification and modification processes of natural dyes and antimicrobials, and their subsequent application on textiles demonstrate the revival of natural dyeing and finishing. Natural dyes have been widely used in textile coloration since ancient times. But, with advent of man-made synthetic dyes in the mid-nineteenth century, the dye market has been captured due to a variety of competitive properties of synthetic dyes against natural ones such as lower cost, higher fastness, color variety, ability to dye synthetic fibers and availability in large industrial scale. However, most of the synthetic dyes raise some serious problems in human health and cause environmental risks. Due to these drawbacks along with the growing awareness about cleaner surroundings and healthy lifestyle, there has been recently a worldwide interest in the production and application of dyes from two natural sources, plants and microorganisms. Most of these natural dyes have also inherently antimicrobial properties and could consequently possess high medicinal activity. They are extracted from different types of microorganisms as well as various parts of the plants that contain coloring materials such as tannin, flavonoids and quinonoids. Here we review the latest scientific researches on extraction and application of natural dyes/antimicrobials on textiles as effective coloring and antibacterial agents. First, different methods of extraction of natural dyes/antimicrobials will be discussed, and then, current methods of textile treatments and examples of early applications of these dyes on textile processing, properties achieved and the results obtained will be presented.     

Metal organic frameworks as adsorbents for dye adsorption: overview,prospects and future challenges

Considering the amount of colored waste water generated from many industries (textile, leather, paper, printing, dyestuff, and plastic) that are sent to various water bodies and the ecosystem, the search for efficient and better methods of purification still continues. With the recent research into metal organic frameworks (MOFs), there is a steady growing interest worldwide for their various applications. This article presents a review of MOFs, their application in dye adsorption and their various challenges and future prospects. It was concluded that with the current interest, research and development for various applications, there are possibilities which will bring to limelight more laboratory, industrial and environmental usage of MOFs as dye adsorbents.     

Removal of textile dyes from aqueous solution using PEG based aqueous biphasic system

Aqueous biphasic systems (ABSs) composed of polyethylene glycol (PEG) and salt have been examined for the removal of textile dyes from textile effluent. The partitioning of four dyes namely Cibacron Scarlet LS 2G, Rhodamine B, Brown ERN and Astacryl Red 3B was investigated. All the dyes studied were found to partition into the upper PEG rich layer. Sodium carbonate was found to be the most efficient salt for extraction of dyes. Sodium sulphate was found to be marginally less efficient. Sodium chloride did not cause partitioning at all. Partitioning occurred at all pH and was almost pH independent. The partitioning of these dyes in larger volume (100?mL) ABS was also demonstrated. Studies using dye bath effluent were also conducted. In all cases very high efficiencies consistently above 98% were obtained.     

Treatment of dye‐containing wastewater by sequencing batch reactor with powdered activated carbon addition

The process involving the combination of powdered activated carbon (PAC) and biomass in the aeration basin of conventional continuous‐flow activated sludge system, known as the PACT process, has proven to be effective for treating toxic pollutants present in industrial wastewaters. In view of the many advantages of sequencing batch reactors (SBR) operationally, the objective of this study is to evaluate the PACT process under SBR operation to treat wastewater containing Acid Blue 25 (AR) and Basic Yellow 2 dyes (BR). The SBR systems were operated with FILL, REACT, SETTLE and DRAW periods in the ratio of 0.25:3.75: 1.0:1.0 for a cycle time of 6 h. The average COD and AR removal efficiencies were 89% and 93%, respectively with PAC addition compared to 76% and 7%, respectively, without PAC addition. In the case of BR, the average removal efficiencies of COD and dye increased from 52% and 9% to 90% and 93%, respectively, with PAC addition. Kinetic study conducted for the REACT period showed that both dyes exhibited a very pronounced inhibitory effect on the activities of the microorganisms. The addition of PAC was capable of reducing the inhibitory effect of only BR but not AR on the microorganisms.     

Separation/degradation behavior and mechanism for cationic/anionic dyes by Ag-functionalized Fe3O4-PDA core-shell adsorbents

● PDA-Fe₃O₄-Ag was made by hydrothermal and oxidation self-polymerization method. ● PDA-Fe₃O₄-Ag had great magnetic separation performance. ● PDA-Fe₃O₄-Ag had good adsorption and degradation performance for ionic dyes. ● PDA-Fe₃O₄-Ag showed NR and MO degradation potential of 91.2% and 87.5%, respectively. High-performance adsorbents have been well-studied for the removal of organic dye pollutants to promote environment remediation. In this study, an Ag nanoparticle-functionalized Fe₃O₄-PDA nanocomposite adsorbent (PDA-Fe₃O₄-Ag) was synthesized, and the adsorption/separation performance of commonly used cationic and anionic organic dyes by the PDA-Fe₃O₄-Ag adsorbent were assessed. Overall, PDA-Fe₃O₄-Ag exhibited a significantly higher adsorption capacity for cationic dyes compared to anionic dyes, the highest of which was more than 110.0 mg/g (methylene blue (MB)), which was much higher than not only the adsorption capacities of the anionic dyes in this study but also other dye adsorption capacities reported in the literature. The dye adsorption kinetics data fitted well to both the pseudo second-order kinetics model and the Langmuir isotherm model, suggesting a monolayer-chemisorption-dominated adsorption mode. Thermodynamics analysis indicated that the adsorption process was both endothermic and spontaneous. Furthermore, the PDA-Fe₃O₄-Ag adsorbent achieved high photodegradation removal rates of the dyes, especially neutral red (NR) and methyl orange (MO), which were 91.2% and 87.5%, respectively. With the addition of PDA-Fe₃O₄-Ag, the degradation rate constants of NR and MO increased from 0.08 × 10⁻² and 0 min⁻¹ to 2.11 × 10⁻² and 1.73 × 10⁻² min⁻¹, respectively. The high adsorption and photocatalytic degradation performance of the PDA-Fe₃O₄-Ag adsorbent make it an excellent candidate for removing cationic and anionic dyes from the industrial effluents.     

Equilibrium,kinetic, and quantum chemical studies on the adsorption of Congo red using Imperata cylindrica leaf powder activated carbon

Leaf powder of spear grass, otherwise known as Imperata cylindrica (IC), was used to prepare activated carbon. The Imperata cylindrica activated carbon (ICAC) prepared was used for the removal of Congo red (CR) dye from aqueous solution. Operation parameters such as initial dye concentration, contact time, adsorbent dosage, pH, and temperature were studied in batch systems. Equilibrium was attained in 150 and 180?min at lowest and highest concentrations, respectively. Maximum adsorption was observed at pH 3. Quantum chemical studies suggested that the protonation of aniline groups and minimal molecular size at planar geometry coupled with electrostatic interaction enhances the adsorption at low pH. Adsorption data were tested using pseudo-first-order and second-order reaction kinetics; the latter was found to be more suitable with a coefficient of determination of ≥0.99. The adsorption process fits Langmuir isotherm model better than the Freundlich model, with a maximum monolayer coverage of 313?mgg^?1. This study shows that ICAC is effective in removing CR dye from aqueous solutions.     

Occurrence of bisphenol A in surface and drinking waters and its physicochemical removal technologies

Bisphenol A (BPA), an endocrine disrupting compound, has caused wide public concerns due to its wide occurrence in environment and harmful effects. BPA has been detected in many surface waters and drinking water with the maximum concentrations up to tens of μg·L^-1. The physicochemical technology options in eliminating BPA can be divided into four categories: oxidation, advanced oxidation, adsorption and membrane filtration. Each removal option has its own limitation and merits in removing BPA. Oxidation and advanced oxidation generally can remove BPA efficiently while they also have some drawbacks, such as high cost, the generation of a variety of transformation products that are even more toxic than the parent compound and difficult to be mineralized. Only few advanced oxidation methods have been reported to be able to mineralize BPA completely. Therefore, it is important not only to identify the major initial transformation products but also to assess their estrogenic activity relative to the parent compounds when oxidation methods are employed to remove BPA. Without formation of harmful by-products, physical separation methods such as activated carbon adsorption and membrane processes are able to remove BPA in water effluents and thus have potential as BPA removal technologies. However, the necessary regeneration of activated carbon and the low BPA removal efficiency when the membrane became saturated may limit the application of activated carbon adsorption and membrane processes for BPA removal. Hybrid processes, e.g. combining adsorption and biologic process or combining membrane and oxidation process, which can achieve simultaneous physical separation and degradation of BPA, will be highly preferred in future.     

Adsorptive removal of rhodamine B from textile wastewater using water chestnut (Trapa natans L.) peel: adsorption dynamics and kinetic studies

Water chestnut peel, an agricultural bio-waste, was used as a biosorbent for removal of rhodamine B (RhB), basic textile dye, from an aqueous solution. The effects of various experimental parameters were studied. The equilibrium data correlated well with a Freundlich isotherm (R² = 0.98–0.99) followed by a Halsey isotherm model (R² = 0.98–0.99) which indicated heterogeneity of the adsorbent surface and multilayer adsorption of RhB dye onto the water chestnut peel waste (WCPW). High correlation coefficients (R² = 0.99) together with close agreement between experimental q_e (0.4–1.7 mg g^?1) and calculated q_e (0.4–2.5 mg g^?1) suggested that the adsorption process followed pseudo-second-order kinetics, with k₂ values in the range of 52–3.4 × 10^?1 g mg^?1 min^?1 at different concentrations. The overall mechanism of adsorption was controlled by both liquid-film and intra-particle diffusions. The negative values of change in Gibb's free energy (?ΔG⁰ = 19.2–29.2 kJ mol^?1) and positive values of change in enthalpy (ΔH⁰ = 30.9–117.6 kJ mol^?1) revealed the process to be spontaneous and endothermic. WCPW was found to be an effective adsorbent for removal of RhB, a cationic dye, from an aqueous solution.