Keywords

1 Introduction

Because of the rapidly rising population and their regular standard of living, freshwater shortages and resources are in grave danger. The removal of manufacturing waste materials and environmental effects like global industrialization are the main reasons for the rise in toxicity and population on a global scale [1,2,3]. As a result of manufacturing growth in textiles, tannery, plastics, and food, the clean water issue has become one of the greatest challenges threatening life in the entire world. Many industrial processes, such as those used to make leather, paper, and textiles, release extremely dangerous and cancer-causing chemicals into wastewater. Scientists estimate that 65% of the number of people worldwide will require tremendous quantities of water in their daily live, and millions of people will experience drinking water shortages [4, 5]. Human health is put at risk because of mismanagement and poor water supply management. In other words, water pollution caused by significant amounts of industrial effluents that are not properly cleaned before being released into sources of water creates a substantial threat to human beings.

The textile industries are receiving a lot of attention from water specialists and scientists due to a large amount of unwanted dye waste entering water bodies. The dyes are harmful to the ecosystem and do not constitute biodegradable. The biological treatment eventually decreases because of the dye effluents from textiles’ ability to block sunlight from entering the aquatic environment, compete with oxygen transfer, and prevent the receiving water from reoxygenating. Therefore, it is inevitable for drinking water to become contaminated with numerous dangerous metal ions and dyes, which have a serious harmful effect [6,7,8]. Millions of dyes are used in a variety of industries, notably textiles, and most of them are extremely poisonous or even lethal to animals and humans, posing a significant barrier to the purification of the world’s aquatic environment. Thus, removing dyes from wastewater is critical in large-scale applications to preserve human health. A range of water treatment procedures is available based on the application and potential of wastewater treatment.

Many methods for removing these compounds from unclean wastewater have been proposed, including flocculation, biodegradation, adsorption, improved oxidation, precipitation, ultrafiltration, ion exchange, electrochemical degradation, and coagulation [9]. Adsorption is regarded as the most promising and financially viable option. Unfortunately, due to reduced capacity of adsorption, sluggish adsorption movement, pricey and difficulty in implementation, many of them are limited. To solve these issues, new materials containing functional groups are constantly required to simplify the water treatment process [10]. Because of their simplicity, cost-effectiveness, and practicality, adsorption techniques have emerged as viable and sustainable alternatives in recent decades. To boost adsorption capabilities, a variety of active compounds have been utilized [7, 9, 11]. Biomaterials are gaining popularity because of their low cost and ability to be prepared from a variety of sources, including agricultural waste. Bio-adsorbents made from shells, lemon peels, maize cobs, mango seeds, tea trash, coconut shells, orange peels and biopolymers like chitosan and alginate are just a few recent discoveries in environmentally friendly products.

To remediate dye-induced wastewater, biodegradable polymers are utilized. These techniques offer various advantages, including simple design, cheap cost, fewer chemical needs, flexibility, and ease of operation. They have received a lot of attention in the latest generations for dye wastewater treatment because of their benefits such as regeneration, simplicity, flexibility, appealing features, and high efficiency. A key strategy for reducing the overuse of industrial activated carbon is the use of biodegradable polymers in water treatment [12, 13]. Even though activated carbon is the most utilized adsorbent, regeneration is difficult and expensive, especially for powdered activated carbon. Agricultural operations generate a substantial amount of garbage. It must be used with caution. It must be borne in mind that the ultimate objective is to rescue the planet. It must also incorporate biomass valorization. Considering these environmental concerns, our effort focused on the development of affordable adsorbents that were persuasive, cheap in cost, non-dirty, and easily disposed of away. Continuous adsorption researches have the potential to assist with the evaluation of processes. It enables us to appreciate and assess the elements, such as the pollutant feed concentration, contact time, solution pH, temperature, stirring rate, and adsorbent mass [14, 15], that have an impact on the phenomena. In this review, we covered a variety of dyes, their impact on the well-being of individuals, parameters influencing this adsorption phenomenon, and a few biodegradable polymers to optimize the elimination of dyes by adsorption. We will offer an overview of the review and future projections for this subject. The use of biodegradable polymers in wastewater treatment aligns with several Sustainable Development Goals (SDGs) by promoting sustainable practices and addressing environmental challenges. Biodegradable polymers can play a role in improving water quality by aiding in the removal of pollutants from wastewater wgixh meets (SDG 6), (SDG 9) and (SDG 12).

2 Dyes in Wastewater

Water is a renewable resource that is required for all life on Earth. It is a “special gift of nature” used for everyday necessities, the timber industry, livestock production, farming, manufacturing processes and other purposes [16, 17]. All of these activities require water, but some dangerous compounds are found in water bodies that contaminate them and make them unusable for bathing, cooking, or other uses. “The water you pollute will always come back to bite you,” is a proverb that perfectly captures the fact that humans are the ones who cause pollution, and as a result, they are suffering from several serious illnesses [18, 19]. Because businesses, industries, and mills release large amounts of dye, water is already polluted. Most of the industries producing dye wastewater are the textile, printing, paper, food processing, and tannery industries as shown in Fig. 1.

Fig. 1
A classification chart of pollutants in wastewater. The 3 types are dyes, heavy metals, and pesticides.

Pollutant types in wastewater

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In addition to acids, glues, salts, and other contaminants, dye effluent also contains auxiliaries that are toxic, teratogenic, carcinogenic, and xenobiotic. The human body experiences these effects as eye burns, skin irritations, allergic conjunctivitis, and occupational asthma. Even though the dye industry produces a variety of pollutants in different amounts [20, 21]. As a result, dye effluent poses a risk to both aquatic and terrestrial environments as well as human health. Because of the tremendous increase in the number and variety of colors used in textile and other industries, dyes are also a significant source of water pollution. These dyes can be categorized as azo, Sulphur, indigo, phthalocyanine, anthraquinonoid, nitro, nitroso, and others, which we will discuss in more detail later in this book. These dyes also have a variety of functional groups. Several pharmaceutical companies poured waste into rivers, possibly triggering a variety of illnesses in those who drank and utilized the water. Water contamination is mostly caused by dyes, heavy metals, medications, bacteria, and others, are mentioned in Fig. 2.

Fig. 2
A radial diagram depicts sources of dyes in the environment. The 4 sources are textile, printing, chemicals, and industries.

Sources of dyes in environment

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3 Environmental and Health Effects of Dyes

Dyes are often used to improve a product’s look and quality. As a result, dye production, processing, and use raise several health and environmental problems. Dye is widely used in the pharmaceutical, textile, food, lather, paint industries, household and wastewater treatment plant. When straight black, methyl red, acid red, acids blue, blue dye, methyl blue, hair products, mordant red dyes, and indigo are used and released into the environment, they damage the ecosystem [22, 23]. Dye effluent contains ammonia, leveling chemicals, hydrochloric acid, acetic acid, soap, formaldehyde, sulfur dioxide, organic polymer, softener, and other compounds [24, 25].

Long-term workers in these dye industries face health concerns when handling, processing, and transporting the colors. Breathing problems, pneumonia, burning, allergens, immune response loss, coughing, cardiovascular disease, skin rashes and itching, and other physical problems are frequently caused by inhalation and ingestion of pollutants. Additionally, dyes can negatively impact human health in several ways, including dermatitis, the central nervous system, the liver, the kidney, the skin, the enzymatic system, the reproductive system, human chromosomes, the neurological system, and the epidermis [26, 27].

Because animals and humans use water for everyday activities including bathing, cooking, drinking, and cleaning, the presence of synthetic dyes in freshwater resources is undesirable. While some textile manufacturers filter their wastewater to dissolve and remove dyes and other industrial wastes, others released dyes and other manufacturing waste straight into sources of water, creating major ecotoxicological problems, inflicting environmental harm, and risking human health.

Because of the dye, sunlight becomes obstructed and is unable to penetrate the bottom of bodies of water, resulting in an oxygen deficit. If dye is present on the surface of water bodies, it is unsightly and produces a foul stench. Ultimately, dye degrades soil quality, productivity, and fertility while polluting the air quality [28, 29]. Wastewater, particularly untreated industrial effluent, was used by farmers in less developed countries to irrigate their crops, which harmed the integrity of the soil, crop growth, and the emergence of seed rates, ultimately harming people or animals. Furthermore, the deterioration of water quality could be caused by wastewater containing color.

Dyeing can obstruct access to the aquatic environment’s photic domain, as well as the absorption and visible reflection of sunlight. As a result, potential ecological concerns include changed aquatic environments and diminished process of photosynthesis. On the other hand, if people consume colored fish and other aquatic foods, it could result in fever, cramps, hypertension, and other medical issues. Dyes can be detected in the environment because of their extensive use, and they physiologically increase in the aquatic ecosystem, including in fish and algal species.

The environment and human health could be harmed by dye wastewater. Therefore, it is important to manage dye-containing wastewater in a way that is both economical and responsible for the environment. A safe, acceptable, and sustainable dye wastewater treatment is critical for preserving human health, reducing environmental harm, and improving environmental protection [30]. The effects of dyes direct and indirect which impact various substrates are shown in Fig. 3.

Fig. 3
An illustrated diagram presents the effects of dyes, plastic, and fibers from the textile industry on plants, humans, water, aquatic animals, and aquatic microorganisms.

Effects of dye on several substrates

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4 Dye Classifications and Applications

One of the things we use the most in our daily lives is dyes, which can be either natural or artificial substances that can be found in many settings. Dyes are now widely used in a variety of sector-specific industries, such as textiles and clothing, personal care items, polymers, and printing [31].

Chromophores and auxochromes are the two main parts of dye molecules. Chromophores provide color, but auxochromes can help by boosting the chromophore’s affinity for fibers and making it more water-soluble. Dyes are chemical substances that can bond to the outer layer of clothing to add color. Synthetic dyes are available in many different kinds of sizes and forms and are categorized according to their chemical composition, color, and purpose of use. Based on their solubility, colors may occasionally be categorized in different ways. Insoluble dyes include azo, dispersion, sulfur, solvent, and vat, while soluble dyes include acid, basic, direct, mordant, and reactive as it is shown in Fig. 4.

Fig. 4
A classification chart of dyes. Natural dyes are from vegetable matter that includes plants, from insects that include lac, and from minerals that include iron oxide. Synthetic water-soluble dyes include acid dyes, water-insoluble include vat dyes, and in-situ color formation includes azoic colors.

Dyes classification based on the source of the material

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Table 2 provides several examples of synthetic dyes and their possible applications, as well as the ingredients necessary and the chemical structure of different dyes as shown in Fig. 5. Dyes combined wastewater is a significant contamination as well as one of the world’s current challenges and burning dilemmas. Dye wastewater is rising because of industrial expansion and human demands. According to the US EPA, 1 kg of fabric requires at least 40 L of clean water, which might vary depending on the textile material and coloring procedure [32, 33].

Table 2 Applications and examples of dyes
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Fig. 5
10 line chemical structures of Xanthine dye, nitro dye, triphenyl methane dye, indigo dye, Myrobolan dye, methine dye, weld dye, azo dye, India dye, and Eosin dye that have furanose and pyranose rings.

Chemical structure of different dyes

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Untreated wastewater from many dye manufacturers has the potential to harm the environment and human health. Dyes have an impact on water quality by interfering with photosynthesis, slowing plant development, infiltrating the nourishment chains, causing accumulation in the body, and perhaps increasing poisoning. Dye effluent contains organic pollutants, hazardous colors, and heavy metals such as mercury, chromium, cadmium, lead, and arsenic. Azo dyes are the most widely used in the manufacturing of textiles, calculating more than 60% of all textile dyes [32, 33].

Azo dyes, such as diazo, monoazo, and triazo, are typically synthetic aromatic colors consisting of two or more N=N groups linked to benzene and naphthalene rings. Azo dyes have a wide range of applications including medications, textiles dyeing, pharmaceuticals, and paper printing. Azo dyes are widely used in the textile industry because they are affordable, stable, and provide a wide range of colors. The following industries contribute to and release dye into the environment: textile businesses (54%), concurrent dyeing businesses (21%), paper and pulp companies (10%), paint and tanneries (8%), and dye producing facilities (7%) as shown in Fig. 6.

Fig. 6
A donut chart depicts the sector-wise distribution of dye-producing industries. Dye manufacturing factories have the highest share followed by paint and tannery factories, paper and pulp factories, dyeing factories, and the textile industry.

Sector wise dye producing industries

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Figure 7 depicts the quantity of dye combinations ejected throughout the textile production process. Among the many different chemical combinations of the various substances used during manufacturing and processing are inorganic compounds, polymers, and natural products.

Fig. 7
A bar chart plots the rate of dye granting in percentage versus 10 textile manufacturing processes. Dyeing is the highest at 85% followed by bleaching at 62%, wet finishing at 58%, scouring at 52%, neutralizing at 33%, desisting at 21%, printing at 13%, others at 10%, and fueling at 2%.

Rate of dye granting in textile manufacturing processes

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5 Biodegradable Polymers-Based Adsorbents for Dyes Removal

Researchers and scientists have employed biodegradable polymers extensively for the adsorption of many contaminants, including colors. Given that they feature a range of functional groups on their backbone, these combined polymers may be readily altered or changed to match the component’s requirements. By effectively adsorbing specific metal ions, polymer selection can also increase selectivity. Due to their simplicity in synthesis, lack of toxicity, low cost, structural strength, stability, high porosity, and low water solubility, conducting polymers have become more popular as adsorbents [25, 38].

Table 3 provides several examples of biodegradable polymers used as adsorbents in dye removal and shows their maximum capacity for adsorption and their condition for removing the specific dye with a specific polymer.

Table 3 Biodegradable polymers-based adsorbents for dye removal
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As indicated in Table 3, Bio-adsorbents derived from agricultural waste such as citrus fruits, olive kernels, shells of palm nuts, peach and apricot kernels, corn husk, coffee beans, fruit waste, nut shells, and biopolymers such as chitosan and alginate are now being studied. The use of biomass in wastewater treatment serves as a key alternative for minimizing the overuse of industrial activated carbon. Agricultural operations generate a substantial amount of garbage. It must be used with caution. It must be borne in mind that the ultimate objective is to rescue the planet. It must also incorporate biomass valorization. Considering these environmental concerns, our effort focused on the development of affordable adsorbents that were persuasive, cheap in cost, non-dirty, and easily disposed of away. Unending adsorption study results give valuable data for process analysis.

It enables us to understand and assess the many variables that affect the phenomena, including the impact of pollutant loading rate, contact length, solution pH, temperature, agitation speed, and adsorbent mass. Adsorption in both batch and continuous columns ought to be used as a method for treating industrial wastewater. In continuous adsorption systems, the concentration in the liquid and solid phases varies across time and space. The design and performance of fixed bed columns present specific problems in the absence of a quantitative approximation model.

For instance, in batch and bed column systems, the ability of citrus peel-alginate compound beads to remove methylene blue (MB) dye from an aqueous solution was investigated. To analyze breakthrough curves, a series of continuous adsorption experiments were conducted, considering three different factors: bed height, input feed flow rate, and feed MB dye concentration.

The results of the batch tests showed that dye adsorption is influenced by the pH of the solution. The high MB removal on UCP/A was found to be 93% at pH 7 [42]. On the other hand, nano-hydroxyapatite was incorporated into a starch-graft-poly(acrylamide)/graphene oxide network to create a nano-adsorbent composite for the removal of malachite green dye from aqueous solutions. The following parameters were used to achieve the highest dye adsorption (297 mg/g): agitation for 60 min, n-Hap content of 3 weight percent, solution pH of 10, and initial dye concentration of 100 mg/L [39]. Technology, natural carbohydrate polymeric materials, tunable materials, and sensitive materials would all benefit from another application of biodegradable polymers as adsorbents to efficiently remove toxins from wastewater at a variety of levels [43, 44].

Consequently, the methyl orange anionic color from contaminated water was removed using natural carbohydrate polymeric materials made from rice flour (RF) and graham flour (GF). In this study, the RF and GF adsorbents showed exceptional selectivity, enabling precise, targeted removal of dangerous dye with high efficacy under ideal experimental conditions. Because of the adsorbent charge reactivity, the pH of the solution was significantly altered. The best experimental technique was used to assess the influence of each influencing element and its interactions. According to the kinetic results, RF and GF adsorbents had slower kinetic capabilities than functional nanomaterials and ion exchange fibrous adsorbents [43, 45, 47].

The monolayer coverage adsorption findings showed a high adsorption capacity of 173.24 and 151.27 mg/g of RF and GF adsorbent, respectively, and were closely associated with the Langmuir isotherms. Foreign anions including chloride, nitrate, and sulfate had no impact on the RF and GF adsorbents’ ability to bind dye. Additionally, during a few cycles, the adsorbed dye on the RF and GF was completely desorbed with ethanol and reconstituted back into its original form for the following removal process. This was done with no appreciable functional loss [46, 48, 49]. Based on the findings of reactivity, selectivity, and applicability, the RF and GF natural carbohydrate polymeric adsorbents may be employed to remove harmful anionic pollutants [50,51,52]. Natural carbohydrate polymeric adsorbents RF and GF might be employed in large-scale applications to remove hazardous anionic dyes and other pollutants to start cleaning up wastewater to preserve population well-being [53,54,55].

6 Conclusion

This study aims to offer an overview of biodegradable polymer-based materials for dye adsorption to combat water pollution. Adsorption removal of contaminants from wastewater is a substantial substitute for cost-effective traditional procedures and the best solution for wastewater treatment as well as for businesses. Dye wastewater-producing enterprises are expanding and discharging more often across the world. Because there is no worldwide norm for wastewater discharge, each country has its own set of guidelines established by its government. Therefore, there are no distinctive, unique, or financially viable solutions to the wastewater curse. Moreover, multiple standard, advanced, and new ways to dye wastewater have been developed and tested. Taking into account neither the rate of dye removal nor the benefits and drawbacks, biodegradable polymers as adsorbents appear to be the most effective and sophisticated for dye removal. The results of this ongoing investigation and numerous model-predicted results demonstrated how toxic dyes are to our health and their influence on the environment, despite their widespread use in industry and other fields. The review also suggests the potential of biodegradable polymer adsorbents as efficient, cheap and environmentally friendly adsorbents for different types of dyes removal from wastewater, as well as how they show a high removal rate and worldwide acceptable that may be used to scale up the procedure to an industrial ecosystem because they performed well in various experiments. Consequently, this study will assist governments and entrepreneurs make the appropriate environmental decisions as it is also relevant to the sixth number of the sustainable development goals (Clean water and Sanitation).

7 Recommendation

Encourage the adoption and utilization of biodegradable polymers as adsorbents in water treatment processes. These polymers offer a more sustainable and environmentally friendly alternative to traditional adsorbents like activated carbon. Collaboration between researchers, policymakers, and industries is crucial to facilitate the implementation and scale-up of biodegradable polymer-based adsorption techniques. Invest in further research and development to explore and optimize the functionalization of biodegradable polymers for enhanced adsorption of dyes. This can include studying different types of biodegradable polymers, their modifications, and their performance under various conditions. Additionally, investigate the use of agricultural waste as a source of biodegradable polymers to reduce costs and promote circular economy principles. The use of sustainable adsorption techniques, including biodegradable polymers, in water treatment processes. Provide incentives and support mechanisms for industries to adopt environmentally friendly practices and invest in.