Sustainable textile dyeing processes

Textile effluents are characterized by high chemical oxygen demand, biological oxygen demand, total dissolved solids, pH and colour. Fabric preparation steps, such as desizing, scouring, bleaching and mercerizing, use various chemicals and plenty of water. The occurrence of unfixed dyes and other electrolytes in effluents poses serious threats to the environment. Available end-of-pipe treatment procedures are either expensive or not efficient; hence, a large number of small-scale industries succumb to this problem. So, finding an alternative eco-friendly process of textile production is of paramount interest. Here, we review three potential eco-friendly systems applicable to textile dyeing processes to minimize salt and water consumption. First, we review application of enzymatic processing in fabric preparation. Secondly, we review the use of biodegradable organic salts, such as trisodium citrate, magnesium acetate, tetrasodium edate and sodium salts of polycarboxylic acids, as fixation and exhaustion agents. Finally, we review various surface modifications of cotton to reduce the volume of effluent and total dissolved solids.     

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.     

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.     

Biopolymer-supported TiO2 as a sustainable photocatalyst for wastewater treatment: a review

The rising water pollution by pesticides, pharmaceuticals and dyes is a major health issue calling for advanced remediation methods such as photocatalysis with titanium dioxide (TiO₂), yet the use of TiO₂ displays issues of aggregation, mass loss, recovery, and reusability. These issues have been recently solved by synthesizing biopolymer-supported photocatalysts using cheap, biodegradable and safe biopolymers such as chitosan, alginate, cellulose, cyclodextrin, guar gum and starch. Here we review biopolymer-supported TiO₂ photocatalysts for the removal of organic compounds, with focus on preparation methods, photo and chemical stability, reusability, and adsorptive capacity. We discuss applications of immobilized photocatalysts at the industrial scale.

     

Studies on the utility of plant cellulose waste for the bioadsorption of crystal violet dye

Several synthetic dyes employed in textile and food industries are discharged into aquatic environment. These visible pollutants in water damage environment, as they are carcinogenic and toxic to humans. The use of cost effective and ecofriendly plant cellulose based adsorbents have been studied in batch experiments as an alternative and effective substitution of activated carbon for the removal of toxic dyes from waste water. Adsorbents prepared from sugarcane baggase, were successfully used to remove certain textile dye such as crystal violet from an aqueous solution. The present investigation potentiate the use of sugarcane baggase, pretreated with formaldehyde (referred as Raw Baggase) and sulphuric acid (referred as Chemically Activated Baggase), for the removal of crystal violet dye from simulated waste water. Experiments were carried out at neutral pH with various parameters like dye concentration, temperature, contact time and adsorbent dosage. Efficiency of raw baggase was found better than chemically activated baggase for adsorption of crystal violet dye. The data obtained perfectly fits in the Freundlich adsorption isotherm.     

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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Seven years from the first application of polyaluminium chloride in the Czech Republic – effects on phytoplankton communities in three water bodies

This study determines the efficiency of polyaluminium chloride application on phytoplankton species as a consequence of five reservoir restorations in the Czech Republic during the years 2005 and 2008, including the first ever large-scale application. Although polyaluminium chloride has been used in water treatment plants across the world, information about its application toward cyanobacterial blooms in nature is poor. Although the application of polyaluminium chloride did not cause any fundamental long-term changes in the composition of phytoplankton species or phosphorus load, instead causing fast and acute removal of the phytoplankton community, it may act as an algicidal compound with fast removal efficiency. All treated water bodies described in our study remained unaffected by cyanobacterial blooms and the hygienic limit for the purposes of recreation was not exceeded in any particular season. This article should serve as notice of the advantages and disadvantages of polyaluminium chloride application, and also warn against the uniform usage of this chemical as a method of reducing phytoplankton species in all types of water bodies where cyanobacteria are present. Moreover, data about the effects on non-target (invertebrates) species and microcystin release from cyanobacterial cells are also mentioned.     

Effect of pH on the sonochemical degradation of organic pollutants

An increasing number of organic compounds are manufactured, consumed, and discarded every year. Incomplete destruction of these compounds in wastewater treatment plants leads to pollution of natural waters, posing great health and ecological concerns. Ultrasound, as an emerging advanced oxidation technology, can quickly and effectively degrade organic pollutants in waters. To improve removal efficiency of organic pollutants in an ultrasonic system, operational parameters, especially pH, have been frequently evaluated and optimized. This review show that pH-induced changes in volatility, hydrophobicity and Coulombic force between the target compound and cavitation bubbles leads to higher degradation at acidic pH for most compounds. In addition, pH also changes free radical formation and reactivity in water during sonication, thereby altering degradation kinetics of target compounds. However, the influence of pH is not always consistent for various organic pollutants covering a broad range of physicochemical properties and reactivities. A systematic investigation on the pH effect is necessary to elucidate how pH alters cavitation bubble dynamics and collapse, radical yield and reactivity, distribution of target compounds in the vicinity of cavitation bubbles, water matrices transformation, and ultimately the degradation kinetics of organic pollutants. This first systematic review provides valuable insight into the pH effects on organic pollutant sonolysis, helps to improve our mechanistic understanding of the sonochemical system, and sheds light on future application of ultrasound in water engineering.     

Removal of basic fuchsin dye from aqueous solutions using graphite oxide modified aromatic polyurethane foam material

Graphite oxide modified polyurethane foam (GO/PUF) was used for adsorption of basic fuchsin from aqueous solution and adsorption conditions were optimized to attain an efficiency of 99.5%. The adsorption isotherm was in agreement with the Langmuir model. Kinetic study followed pseudo-second order. Determination of Gibbs free energy and enthalpy change of adsorption indicated spontaneous and endothermic adsorption behavior, suggesting that the adsorbent had a potential for the removal of dyes from industrial wastewater.     

Construction of MOFs-based nanocomposite membranes for emerging organic contaminants abatement in water

● Application of the MOF-composite membranes in adsorption was discussed. ● Recent application of MOFs-membranes for separation was summarized. ● Separation and degradation for emerging organic contaminants were described. Presence of emerging organic contaminants (EOCs) in water is one of the major threats to water safety. In recent decades, an increasing number of studies have investigated new approaches for their effective removal. Among them, metal-organic frameworks (MOFs) have attracted increasing attention since their first development thanks to their tunable metal nodes and versatile, functional linkers. However, whether or not MOFs have a promising future for practical application in emerging contaminants-containing wastewater is debatable. This review summarizes recent studies about the removal of EOCs using MOFs-related material. The synthesis strategies of both MOF particles and composites, including thin-film nanocomposite and mixed matrix membranes, are critically reviewed, as well as various characterization technologies. The application of the MOF-based composite membranes in adsorption, separation (nanofiltration and ultrafiltration), and catalytic degradation are discussed. Overall, literature survey shows that MOFs-based composite could play a crucial role in eliminating EOCs in the future. In particular, modified membranes that realize separation and degradation might be the most promising materials for such application.     

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.     

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.     

Nanosized magnetite in low cost materials for remediation of water polluted with toxic metals,azo- and antraquinonic dyes

Nanosized magnetite has emerged as an adsorbent of pollutants in water remediation. Nanoadsorbents include magnetic iron oxide and its modifiers/stabilizers, such as carbon, silica, clay, organic moieties (polymers, aminoacids, and fatty acids) and other inorganic oxides. This review is focused on the recent developments on the synthesis and use of magnetic nanoparticles and nanocomposites in the treatment of contaminated water. The emphasis is on the influence of the iron oxide modifiers on some properties of interest such as size, BET area, and magnetization. The characteristics of these nanomaterials are related to their ability to eliminate heavy metal ions and dyes from wastewater. Comparative analysis of the actual literature was performed aiming to present the magnetic material, its preparation methodology and performance in the elimination of the selected pollutants. Vast information has been properly summarized according to the materials, their properties and preferential affinity for selected contaminants. The mechanisms governing nanomaterial’s formation as well as the interactions with heavy metals and dyes have been carefully analyzed and associated to their efficiency.     

扰动强化污染底泥有机物自净的研究

扰动能够强化水体溶解氧的恢复并加快传质,增强水体的自净作用,有利于水体和底泥COD的降解,是一种常用的污染水体的修复方法。文章通过人工模拟的水体,构建搅拌和曝气两种上覆水扰动条件,研究了在这两种条件下水体中有机物含量以及底泥中微生物量的变化情况,探讨了扰动对水体有机物去除的影响。研究结果表明：（1）与对照情况相比,在搅拌、曝气条件下水中ρ（溶解氧）分别由0.2 mg.L^-1提高到1.0和8.0 mg.L^-1左右;曝气条件下底泥中蛋白含量及细菌数均最高;（2）底泥中w（脱氢酶活性）在搅拌和曝气条件下分别为0.52和0.46μg.g^-1左右;（3）曝气条件下对上覆水中有机物的去除呈现出较好的降解趋势。因此,运用曝气技术既能加速有机物的生化降解,改善水质;又可强化水体溶解氧的恢复,创造了微生物生长繁殖的适宜环境,增强了水体中微生物的活性,促进了水体自净能力的提高,在治理河道污染的应用中具有广阔的前景。     

Mechanisms of arsenic removal from water

In this review paper, various methods for arsenic removal from water have been described by explaining the related mechanisms of each methods. Advantages and drawbacks were discussed. Membrane methods were suggested as reliable methods for elimination of arsenic from water in addition to other conventional separation methods.     

Efficient arsenic depollution in water using modified maize powder

This article reports the synthesis of an efficient, low-cost material from maize powder to depollute arsenic-contaminated water. Arsenic is toxic for humans and other organisms even at low concentrations. The most well-known and severe case of arsenic poisoning through drinking water has been found in India and Bangladesh. Numerous inorganic materials have been tested for the removal of arsenic from water bodies over the last two decades. However, all such materials have several disadvantages such as unpredictable arsenic ion removal, high cost and the generation of toxic sludge that is often more difficult to manage. Alternatively, organic material from agricultural waste may be modified to enrich functional groups responsible for As sorption and, in turn, used to depollute contaminated waters. Here, Zea mays cob powder has been modified to remove arsenic species from water. Two modified materials were produced: an aminated maize powder and a thiolated maize powder. Amination was done using epichlorohydrin and dimethylamine. Thiolation was done using thioglycolic acids. Amination increased As (III) sorption from 70 to 75.8 % and As (V) sorption from 85 to 94.42 %, compared with unmodified maize powder. Thiolation increased As (III) sorption from 70 to 81.7 % and As (V) sorption from 85 to 90 %. Amination increased usability cycles from 3 to 5. Thiolation increased usability cycles from 3 to 6. The novel modified maize biosorbent has enough potential for the development of a low-cost technological pre-treatment step, prior to high-tech chemical treatments.     

Silver–magnetic nanocomposites for water purification

There is a need for protecting and tidying up the natural resources of water, largely polluted by human activities. Impure water leads to health issues, especially in rural areas. Though various techniques had been used for years to purify water, research is still carried out to find out advanced treatment protocols. Here we review the application of nanomaterials to disinfect and purify water resources. We present micro-organisms responsible for waterborne diseases; physical, chemical and biological treatment systems; and disinfection using silver–magnetic nanocomposites.     

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。     

邻苯二甲酸酯降解细菌的多样性、降解机理及环境应用

邻苯二甲酸酯(phthalic acid esters,PAEs)是一类对人体内分泌系统有干扰作用的持续性有机污染物(persistent organic pol utants,POPs)。PAEs在环境介质如水体、底泥和土壤中长期赋存会对生物体产生毒害效应,其分布广、浓度高和难降解等特点是限制有效环境治理的主要因素。作为环境的重要组成部分,微生物对污染物有很强的适应能力和高效的降解能力,这为PAEs的生物修复提供了可能。与物理化学修复法相比,微生物修复技术具有可控性强、修复面广和灵活性高等优势。本文综述了已报道的大部分PAEs降解细菌的种类及其代谢机制,并分析了其在PAEs污染水体和土壤修复中的应用现状与前景,以期为PAEs环境行为与生物修复研究提供参考。     

Strategies to design modified activated carbon fibers for the decontamination of water and air

The rapid industrialization has induced the entry of organic and inorganic contaminants into the environment at a rate greater than environmental cleaning. As a consequence, pollutants have accumulated in environmental media, thus posing health risk for living organisms. Here, we present surface treatment strategies that modify physicochemical properties of activated carbon fibers for environmental remediation. In particular, we review metals, metal oxides and various advanced materials used for modifying activated carbon fibers. We discuss the utilization of modified activated carbon fibers for adsorption of organic pollutants and inorganic pollutants, and for the degradation of organic pollutants by photocatalysis, electrocatalysis, Fenton process and dielectric barrier discharge. We also discuss air pollutant removal, capacitive deionization, removal of inorganic ions and microbial decontamination by modified activated carbon fibers.