Screening the six plant species for phytoremediation of synthetic textile dye waste water

Most of the dyes are carcinogenic and mutagenic in nature. Plants are potential candidates to remediate textile dye wastewater from contaminated sites. The present study aimed toscreen potential plant species for removal of synthetic dye solution of triarylmethane dye Methylene Blue (MB) and diazo dye Congo Red (CR). Six plant species were screened for their phytoremediation ability for the removal of dyes present in synthetic wastewater. Six plants selected for screening areTrachyspermum ammi L. (T. ammi), Tagetes erecta L. (T. erecta), Hibiscus rosa-sinensis L. (H. rosa- sinensis), Chrysanthemum indicum L. (C. indicum), Bryophyllum fedtschenkoi (B. fedtschenkoi), Catharanthus roseus L. (C. roseus). The phytotreatment of dyes was done up to 40 hfortwo different concentrations of dyes 10 mg L − 1 and 20 mg L − 1 . Among these plants, the maximum decolouration was obtained from T. ammi plant followed by B. fedtschenkoi plant. Both of these plants showed active growth even after the phytoremediation process. T. ammi decolourised the MB dye 99% (10 mg L − 1 ) and 86% (20 mg L − 1 ) while the decolourisation of the CR dye solution was up to 95% (10 mg L − 1 ) and 84% (20 mg L − 1 ).T. ammi found to have maximum potential among screened plants for the removal of MB and CR dye from synthetic dye solution and can be used for decolouration of synthetic dye wastewater.


Introduction
Due to the increasing world population, there is a tremendous growth of various industries, which uses many harmful chemicals for the generation of a commodity for public demands but the side products such as contaminants not only affect water bodies but also the air and soil. Dyes have a major demand and application in the textile industries for the dyeing process. About 10-15% of the azo dyes get lost in the e uent during the dyeing process [1] and 50% other reactive dyes reported for use in the textile industry which throw waste into water [2]. Azo dyes are extensively used in the dyeing process. The e uent containing dyes released into the surrounding thereby seriously affecting the atmosphere by destroying the ecosystem, causing water pollution, and reducing light penetration for aquatic life [3].Due to textile dye wastewater, the Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), suspended solid values enhance [4]. So, there is a big challenge to treat textile dyes e uent before released into water bodies.
There are so many physical and chemical strategies, for example, adsorption, coagulation, sedimentation, occulation, ltration, photodegradation, and chemical oxidation, are accessible for managing contamination produced by textile dyes [5]. These strategies relate to the high expense, low productivity, require huge space and undependable to work. Because of these issues, there is a requirement of the advancement of productive, savvy strategy for the treatment of textile dyes [5].Biological methods are more effective than physical and chemical methods to treat the textile dye wastewater Bioremediation is a very e cient treatment for removing contaminants from textile dyes e uent [6]. Different enzymes and microorganisms were used for removing the dyes from wastewater. Phanerochaete chrysosporium, the most spacious studied white-rot fungus, used to metabolize and decolourise dyes colour and compounds [7]. Biological decolourisation of lignin-containing pulp and paper wastewater using white rot fungi Tictoporia species due to the high oxidative potential of many of the enzymes linked with white rot fungi as ligninase, laccase, Mn-peroxidase [8]. Aspergillus avipes fungus was reported to decolourise the dye xiron orange [9].From the different bioremediation process, phytoremediation is an energy-e cient, solardriven process to remove the contaminants from soil, air, water [10]. Phytoremediation is also used to remove pollutants from textile dye wastewater [11].There are various phytoremediation mechanisms as phytoextraction, phytodegradation, rhizo ltration, phytostabilization, phytovolatilization which helps in the dye removal [12]. Due to these different qualities, we can use plants for the treatment of textile dye wastewater. In the present study, the main focus is to screen the potential of ornamental plants for removing the textile dyes from wastewater.
Different ornamental plants are utilised for phytoremediation study such as Marigold, Euphorbia, Bryophyllum, etc. These ornamental plants are widely used as hyperaccumulators for metals for removal of heavy metals from soil, water and air. Euphorbia pithyusa is proved to be as phytostablizer to remediate low trace element concentration in highly contaminated soils [13]. Marigold variety T. erecta has leaf plasticity when exposed to Cr, indicating the presence of the tolerance mechanism to Cr [14].
Decorative plants are also used for the treatment of dye wastewater as Hibiscus sabdariffa is used to treat CR dye [15]. Ipomoea hederfolia plant is reported for treatment of Scarlet red dye [5]. The petunia grandi ora plant reported to remove the triphenylmethane textile dye Brilliant Blue G [16]. The main investigation of this research to nd and screen the new ornamental plants which have the ability to decolourise the textile dye waste water. Textile dye e uent treated with wild plants such as Blumea malcolmii [17], Rheum rabarbarum [18], Typhonium agelliforme [19], Rumex hydrolapathum [20], and Phragmites australis [21].Aquatic plants are having potential to decolourise and detoxi ers of wastewater containing dyes. They are experimented at laboratory scale studies for degradation of dyes in situ [22].Recently, some tested plants areaquatic macrophytes such as Ipomoea aquatic [23], Salvinia molesta [4], Typha angustifolia [24].Garden ornamental and owering plants such as Glandularia pulchella [25], Petunia grandi ora [16], Portulaca grandi ora [26], Aster amellus [27] and Ipomoea hederfolia [5] have also been observed as potential candidate for degradation of textile dyes. The petunia grandi ora tissue culture plantlets have the potential to decolourise the Brilliant Blue-green dye [16]. Plants and bacterial consortium of Portulaca grandi ora and Pseudomonas putida showed complete decolourisation of a sulfonated diazo dye direct red 5B [26]. Aster amellus Linn used to decolourise a sulfonated azo dye Remazol Red (RR), a mixture of dyes and a textile e uent [27]. Phragmites australis is commonly used in constructed wetlands either for domestic sewage or industrial e uent ts treatment [21]. The aerobic mineralization mechanisms of Acid Orange 7 (AO7) in a Vertical Flow Constructed Wetland (VFCW) planted with Phragmites australis suggested thatAO7 degradation pathway may involve enzymes like peroxidases (POD), known to degrade some recalcitrant contaminants [21].Glandularia pulchella explored to decolourise the dye green HE4B [25], Ipomoea hederfolia ornamental plant able to decolourise the dye mixtures and scarlet red dye [5]. Nerium oleander plant is used to remove uoride in comparison to Portulaca oleracea and Pogonatherum crinitum [28]. Nerium oleander plant also has ability to phytoextract the Cr and Ni heavy metals [29]. Alcea rosea plant has the potential to remove disperse red of heavy metals from the soil, as the T. erecta plant was used to remove Ni and Pb from the soil [31]. Comparison of Chrysanthemum indium plant is exhibited with Dahlia and Calendula for the removal of the Cr metal from the soil [32]. C. indium plant is used to remove CR dye in which ower of the plant act as an adsorbent to remove the CR dye [33]. Bryophyllum pinnatum indicated the tendency to remove Co, Pb, Zn from the soil in comparison with other plants such as Telfaira occidentalis, Talinum triangular. Bryophyllum pinnatum is capable to remove the heavy metals such as Cd, Cr, Cu, Ni, Pb, V [34]. Hibiscus plant helps to eradicate the Cadmium from the soil [35]. C. roseus plant used to remove Cr metal from the soil such as roots, leaves and stems [36]. This research study is aimed to assess the textile dyes removal by using selected ornamental plants as T concentrations as 10 mg L − 1 and 20 mg L − 1 . The whole apparatus was sterilized before experimentation. Table 1 shows the description of screened plants used for the research study. Where A 0 is an initial concentration of dye and A 1 is a nal concentration of dye. All the decolourisation experiments were performed with the same time limit and average values were determined. Both biotic and abiotic controls were also maintained as shown in Fig. 2. The abiotic controls contained the MB and CR dye solution without plants whereas plants in distilled water were kept as biotic controls.

Results And Discussion
The treatment of synthetic dye was done hydroponic system, instead of soil [39].The growth of the plant was observed in the distilled water up to 7 days and then plants were exposed with dyes. The results of each plant were compared with the controlled dye solution. The adsorption on the roots of plants was detected which was responsible for decolourisation. The absorbance was documented up to 40 h. From the absorbance value, the decolourisation percentage was determined. The result data suggested that T. ammi plant was the best in decolourisation and in survival. of CR dye were 95% and 84% respectively. The plant remains survived after adsorption of dye into the roots. However, percentage decolouration decreases with increase in the concentration. These outcomes showed that T. ammi plant is an outstanding plant to decolourise the azo dye CR and triarylmethane dye MB at lower concentration. The decolouration graph of MB and CR dye by using B. fedtschenkoi plant was shown in the Fig. 3 (c)   Wilting of the plant takes place after treatment of CR dye. The plant was not able to treat with more dye concentration than 20 mg L − 1 . Hence, C. indicum is not suitable for the phytotreatment of CR dye synthetic wastewater.
T. erecta plant was also used for a screening test to remove MB dye from synthetic wastewater. It was observed that plant had the more capacity to decolourise the triarylmethane dye, MB in comparison to CR dye. Figure 3 (g) and (h) shows the decolourisation (%) of MB and CR dye respectively. The decolourisation for 10 mg L − 1 and 20mgL − 1 MB dye waste water was 84% and 68% respectively. After decolourisation the MB dye plant shows withering. Initially, the leaves become dry then subsequently stems and roots. Due to these conditions, plant was no more active for treatment with more MB dye concentrations than 20mgL − 1 . The percentage decolouration was observed 67% & 66% for 10 mg L − 1 and 20 mg L − 1 CR dye concentrations respectively. Though, plant was able to decolourise the azo dye, CR and MB but T. erecta plant dryness after removal of the toxic dye makes it unsuitable for the treatment of synthetic dye waste water.  The decolourisation percentage obtained for MR 10 mg L − 1 and 20 mg L − 1 was 35% and 34% respectively and 48% and 43% for CR 10 mg L − 1 and 20 mg L − 1 respectively. In case of C. roseus plant, it was found that plant remain active after dye removal however plant removal rate is quite slow for both the dyes. It was observed that plant could not effectively decolourise the synthetic waste water up to 40 h.
All these decolourization results and impact of synthetic dye waste water on growth of plant used for screening were summarized in Table 2. Hence, the results obtained from the screening experiments clearly indicate that the maximum percentage decolourisation obtained from the T. ammi plant followed by B. fedtschenkoi and both the plant also remained active after removal the both MB and CR dyes. C. indicum and T. erecta plants also showed their potential for decolourisation of synthetic dye waste water however, their survival rate makes them insigni cant for phytoremediation process. H. rosa-sinensis plant was also not considerable for survival because owers withered after dye removal. The plant C. roseus able to bear the toxic impact of dyes but the rate of decolourisation is quite slow for both MB and CR dyes. In the preceding work, the removal of MB was also reported through phytoremediation process with the help of aquatic plant Eichhornia crassipes and Lemna minor [40,3]. The researcher reported that E.
Crassipes removed the colour of MB dye (50 mg L − 1 ) in 20 days experiment up to 98.4% while L. minor (2 g) was exposed into 50 mg L − 1 of MB dyes for 24 h decolourise up to was 80.5 ± 0.4%. L. minor has potential as a phytoremediation agent to remove MB dye from wastewater. In the present research work, T. ammi plant showed the decolourisation up to 99% (10 mg L − 1 ) and 86% (20 mg L − 1 ) for MB dye in 40 h experiment only. Hence, T. ammi plant proven to be more effective than E. crassipes and L. minor.The earlier works of CR dye removal by water hyacinth up to 94.5% [41,43]. The maximum decolourisation up to 95% and 84% from the 10 mg L − 1 and 20 mg L − 1 CR dye concentrations respectively by T. ammi. The maximum dye was found to adsorb on the roots of T. ammi plant and it is possibly due to rhizo ltration process, plant could able to give maximum decolourisation. Therefore, T. ammi plant acts as potential candidate for future research where it can be used as phytoremediator for decolourisation of dye waste water.

Conclusion
The results from present research support the ability of six screened plants for removal of MB and CR dyes. T. ammi and B. fedtschenkoi are the e cient plants for removal the both dyes. Moreover, survival of both the plants seems to be signi cant. Maximum percentage of decolourisation obtained from the T.ammi plant as 99% (10 mg L − 1 ), 86% (20 mg L − 1 ) for MB dye and 95% (10 mg L − 1 ), 84% (20 mg L − 1 ) for CR dye because of maximum adsorption on the roots of the plant. Therefore further research work can be focus on the dye removal by using T. ammi plant on the bases of adsorption mechanism.

Declarations
• Availability of data and materials: Not applicable

• Competing interests:
There is no personal or nancial con ict of interests among the authors to publish this manuscript.
• Funding: There is no funding for this research work.
• Authors' contributions: Navjeet Kaur : Conducted the experimental studies and drafting the manuscript; Jyotsna Kaushal: Conceptualization, expert view and overall Supervision; Pooja Mahajan: Data interpretation; Arun L. Srivastva: Suggestions and interpretation on the chemical analysis All authors read and approved the nal manuscript.
• Acknowledgements: Figure 1 Chemical structure of (a) MB dye (b) CR dye.  Decolourisation potential of different screened plants for MB and CR dye solution