Novel Materials for Dye-containing Wastewater Treatment

The presence of dye in water stream leads to unexceptional effects on living life. As dyes are consumed globally from small-scale to large-scale industries inculcating tanneries, food, cosmetic, textile, medicinal sectors with the production of 1,000,000 tons all over the world. Majorly, the textile sector plays a pertinent role in dye emissions into the ecosystem. Only dying industries discharge about 7.5 metric tons annually. The complex structures of dye comprising of aromatic rings bonded with different functional groups having π-electron could absorb light within 380–700 nm spectra. They impart coloration due to the presence of chromogens and chromophores. Out of several natural and synthetic dyes, azo group proliferation has been highly carcinogenic due to amine and benzidine emissions. Besides this, the fact of being non-biodegradable makes the dye molecules last longer in the environment producing hazards. Henceforth, eradication of dye molecules from wastewater is thus needed before discharging the stream into the environment with long- and short-term effects. The severe implications have been reported for the aquatic life due to direct contact. Whereas to human life, there were observations from skin irritations to cancer-like disease. Several approaches were reported for the treatment of dye-containing streams but the exploration for the best available technique is still ongoing. So, this chapter collects comprehensive facts about dyes, its harmful effect, and approaches for the treatment at a worldwide level and Indian perspective. Additionally, the article draws out the comparative analysis for available techniques and states the recent advancements for the purification of dye-containing wastewater.

Industrialization, modernization and improper agricultural practices have led to the discharge of many diverse pollutants in the environment, threatening the lives of humans and the ecosystem. Water pollution is one of the most important issues that humans are dealing with. Up to now, many attempts have been conducted to remediate and treat polluted water. Environmentally biomaterials are of great alternative for water purification, particularly due to their promising properties, including cost-effectiveness, availability, non-toxicity, and excellent performance. Accordingly, the present chapter explores the utilization of some biomaterials, namely, chitosan, Luffa, sisal, and hydroxyapatite within the field of water and wastewater technology for the removal of dyes, heavy metals, and pharmaceuticals. The consideration of these three groups of pollutants is mainly because of the fact that in actual water media, these may come all together. In addition, the fundamentals of the adsorption process as well as isotherms/kinetics models and thermodynamic parameters are well discussed.

Textile, leather and paper goods require a huge amount of synthetic dyes for their colouration. During colouration and other wet processing treatments, a considerable amount of dye remains in the aqueous bath as unused. This unused dye is the major constituent of effluent and a serious concern to the water pollution. In the past two decades, many biopolymers have been extensively studied for the removal of dyes, heavy metal ions and other contaminants from effluents. Due to the biodegradability, nontoxicity and outstanding chelation behaviour, chitosan and its derivatives have been considered as prospective biosorbents to capture the dissolved dyes from aqueous solutions. Further, the ability of this biopolymer to be shaped into flakes, powders, beads, gels, films and porous particles expands its practical applicability. This write-up is an attempt to highlight the relevancy of the chemical structure of chitosan for dye removal applications. The mechanism of working of chitosan and the process parameters affecting the efficiency of dye removal have also been discussed. The recent modifications carried out in the physical and chemical structure of chitosan to improve its dye adsorption capacity have also been thoroughly investigated. Moreover, some practical constraints limiting its usage for dye removal application have also been a part of this chapter.

Dyes are employed in an assortment of manufacturing products, including textiles, paints, plastics, beverages, pharmaceuticals, and cosmetics. Dyes discharging in effluents is a big environmental concern, resulting in a high decline of water quality and destruction of the aquatic ecosystem. Various conventional routes to treat with the effluents containing dyes, such as filtration, coagulation-flocculation, and adsorption have been extensively studied, however; these processes are based only on the transportation of dyes to another phase without destroying them this is not cost-effective because an additional step to achieve a full treatment must be applied. The only way to resolve the environmental problem is to remove these dyes from effluents by degrading them into non-toxic materials. Recently the degradation of organic compounds via photocatalysis using semiconductors is considered a promising process; metal-based oxides are reported to be an efficient photocatalyst to break down the organic dyes. Here, we summarize the most up-to-date information on dye degradation using a new promising nanocomposite. Their synthesis process and photocatalytic mechanism of the hybrid structure have been addressed. The effectiveness of photocatalytic removal in comparison to traditional approaches has all been examined.

Photocatalysis, being a sustainable and environmentally friendly technology with potential for low-cost applications, is one of the most researched methods for dye decolourization. Among the various photocatalysts available, TiO₂ is a highly efficient and stable photocatalyst. Even though reports of scientific studies on the use of TiO₂ dates to 1930s, wider attention and numerous studies on its application as a photocatalyst for environmental remediation started after the study by Fujishima and Honda in 1972. The use of pure TiO₂ as photocatalyst is limited due to its high band gap energy and recombination rate. Also, the photo excitation of TiO₂ is in the ultraviolet (UV) range and consequently, only 5% of the total solar energy could be utilized for photocatalysis with pure TiO₂. Another limiting factor affecting the efficiency of degradation is mass transport limitation and agglomeration of the photocatalyst. This chapter reviews composites with metals, non-metals, semiconductors, carbon derivatives and other support structure, which are developed to tackle the limitations of photocatalysis with pure TiO₂. Metal-doped photocatalysts aid in reduced recombination and visible light photocatalysis. Non-metal doping leads to band gap modification and redshift. Heterojunctions with semiconductors as photosensitizer or electron sinks are possible. Carbon derivative-based composites and support structure-based composites also are studied extensively. Of late, co-modified composites are gaining importance. Overall, this book chapter intends to take the readers through the journey of development and application of TiO₂-based photocatalysts for dye degradation with emphasis on composites.

Conventional methods used in dye removal have limited efficiencies. Due to its eco-friendliness and other desirable characteristics, such as biodegradation, environmental friendliness, nontoxicity, excellent thermal and mechanical properties, and ease of modification, cellulose has found application in fabrication of membranes for dye removal from wastewater. Unlike the bulk form, the properties of nanocellulose include high mechanical strength and high surface area, giving it potential for the fabrication of high-efficiency membranes. This stems primarily from the abundant surface OH groups. Moreover, nanocellulose affords a high aspect ratio, a large population of active binding sites, resulting in high adsorption capacity for a range of pollutants including dyes. The major challenge in the design of nanocellulose-based membranes is ensuring adequate access to reactive sites, together with maintaining high flux and mechanical stability. Generally, incorporating nanomaterials into the membrane matrix reduces fouling. This chapter reviews literature on the use of nanocellulose-based membranes in the remediation of dye-polluted wastewater. The specific objectives are: (1) to evaluate literature on the synthesis and fabrication of nanocellulose-based membranes and (2) to link the physico-chemical properties of the membranes to their dye removal performance.

Industrial effluents of dyes is a vital source of water pollution, their release from textile industries into surface water affects the ecosystem by generating oversized volumes of outlets mixed with several dyes. These dyes cause harmful health effects and lead to significant health concerns to humans and affect the environment. This chapter implements a contribution to environment in a sustainable view through adsorption and biosorption approaches to remove the methylene blue (MB) dye from aqueous solutions and from a real effluent of textile industry. In this survey, efficiencies of several adsorbents such as mineral, organic, synthetic, and low-cost materials are established. A brief insight into methylene blue dye removal mechanism and comparison among various adsorbents—Duste Apatite (DA), Phosphogypsium (PG), Raw Clay (RC), Glebionis coronaria L. (G. coronaria L.), Diplotaxis Harra (D. Harra), acidic and basic sawdust acacia (A-HCl and A-NaOH)—along with their sorption properties and their characteristics are discussed. Due to its good sorption capacity, chemically treated acacia tree sawdust has been successfully applied for eliminating textile dyes from wastewater. A real final effluent of a textile industry was thus treated by sorption on both acidic and basic chemically treated acacia tree sawdust.

Textile dyeing wastewaters is one of the most difficult to handle. The aim of this paper to investigate the removal capacity of two azo dyes, including Brilliant green and Alizarin red S from the aqueous solution by three types of activated carbon prepared from bamboo leaves AC30 (650 °C/30 min), AC45 (650 °C/45 min) and AC60 (650 °C/60 min). All three samples displayed the functional group represented by the azo dye removal capacity such as C=C; C–O–C, O–H and showed high C content (over 72%). With the highest BET surface area up to 108.9202 m²/g, the AC60 material sample recorded the maximum efficiency of 100% at the reaction time of 30 min with the volume ratio of azo dye/distilled water of 2/18 (mL), pH 9, the absorbent amount of 0.5 and 2 g for Brilliant green and Alizarin red S, respectively. This study is an overview of the azo dye removal capacity in initial textile dyeing wastewater sample and compares the quality of AC60 material sample to four commercial activated carbon samples, including AC-R (Russian activated carbon), AC-C (Chinese activated carbon), AC-F (French activated carbon) and AC-Tra Bac (Vietnamese activated carbon from coconut shell). The analysis results also showed that the azo dye removal efficiency of the AC60 material synthesized from bamboo leaves is higher than some previously prepared material (AC-C material reached only 90.5 and 82.55% for Brilliant green and Alizarin red S, respectively) and achieved the maximum adsorption efficiency 100% after 30 min reaction time. These findings indicated that the removal efficiency for azo dye depends on experimental conditions such as reaction time, pyrolysis temperature, pH… and the source of the raw materials also has a great influence on the carbonaceous material structure, determining the treatment efficiency as well as the removal capacity for pollutants.

Pharmaceuticals are regarded as one of the prominent environmental concerns due to their entrance and detection in aquatic solutions. Some pharmaceuticals are able to generate colouring agents in water which must also be removed. This chapter focus on the removal of rifampin, a drug producing a reddish-orange to reddish-brown colour in water, by Luffa biomaterial. The bioadsorbent was characterized with SEM, XRD, and FTIR. In view of experimental tests, it turned out that equilibrium reached in 140 min, and at a concentration of 5 ppm, the removal efficiency of approximately 100% was achieved. The highest rifampin removal was observed at 25 °C. The kinetics and isotherm studies let out that the experimental results followed pseudo-second-order, Elovich, and Langmuir models. It is fair to suggest that based on the results, Luffa biomaterial could be nominated as a sustainable, non-toxic and rifampin removal that can adsorb it from aqueous solutions