1 Introduction

Water is the central element of all socioeconomic activities, irrespective of the developmental stage of a particular society. With the rise of industrial activities, sectors like automotive, chemical, stationery, and notably textile manufacturing, are generating significant quantities of organic dyes. The compatibility between dyes and textiles is influenced by both the chemical composition of the dyes and the characteristics of the fibers onto which they are applied [1].

The prevailing water regulation, outlined in Law 10–95, incentivizes industrial entities to manage their effluents effectively, underscoring the necessity of implementing tailored treatment systems that integrate decolorization units to mitigate pollution to the fullest extent. Simultaneously, Decree 2-09-683, ratified on July 6, 2010, outlines the procedures for formulating the regional strategy for handling non-hazardous industrial, medical, and pharmaceutical waste, as well as remaining, agricultural, and inactive waste. It also specifies the steps involved in conducting the public consultation associated with this strategy.

Appropriate treatments must eliminate residual dyes in the dyeing or washing baths before evacuation into the receiving environment. These non-biodegradable effluents pose aesthetic and health problems due to toxic micropollutants [2,3,4,5]. The concentrations of dyes such as Red 141 and Methylene Blue in textile effluents can vary significantly depending on numerous factors. These factors include the type of dyeing process, the efficiency of wastewater treatment systems, and dilution in discharge systems. Therefore, it is difficult to determine a specific range of concentrations of Red 141 and Methylene Blue in industrial waste. The concentration values of dyes in textile effluents can vary depending on the specific conditions of the factories and treatment processes used. However, typical concentration ranges found in the literature are 20–200 mg/L for Red 141 (or similar dyes) and 10 to 150 mg/L for Methylene Blue [2,3,4].

Various physicochemical methods have been explored to address the discoloration of textile waste. These methods include coagulation-flocculation, oxidation, adsorption, and membrane filtration. Extensive research has demonstrated their effectiveness in removing color from water [6, 7]. Conversely, processes involving biological treatment methods are not used mainly in treating water polluted by dyes due to their low biodegradability. Physicochemical-biodegradation coupling is used on an industrial scale to eliminate pollution caused by dyes [8]. Other Physicochemical methods are currently employed, such as chlorination, ozonation, and reverse osmosis, all of which significantly differ in color removal, operation, and financial cost [9].

Adsorption is frequently employed as a primary method for water cleanup. For instance, the use of commercial activated carbon (CAC) has emerged as a preferred technique for adsorbing pollutants, highly effective and straightforward in its application. The fundamental concept behind adsorption treatment involves capturing dyes with a solid substance referred as an adsorbent. Additionally, different solid substances, including clays, zeolites, activated aluminas, peat, biomasses, biopolymers, agricultural residues, industrial by-products, polysaccharides, starch, alginates, etc., can also be employed in processes aimed at decolorizing water [10,11,12]. Researchers have been focusing on finding alternative and cost-effective adsorbents, preferably derived from natural substances and local waste materials. Following the same framework, the present study aims to develop the discoloration of the water to promote a co-product of the fish processing industry, i.e., Cuttlebone (Sepia Officinalis). Many studies have been conducted to reuse cuttlebone for supplementing birds' calcium intake and in biomedical sciences and cosmetics. Calcium carbonate represents up to 90% of the composition of cuttlebone [13,14,15,16,17].

This study evaluates the maximal adsorption capacity of cuttlefish bone (Sepia Officinalis) regarding two organic dyes, Reactive Red 141 of an anionic nature and methylene blue of cationic nature (BM). Efforts are also underway to examine how different factors impact the efficiency of adsorption, encompassing the adsorbent's weight, pH values, contact duration, and the initial dye concentration. MC and MD were employed to simulate the adsorption of Red 141 and MB onto calcium carbonate surfaces and better understand their interaction process.

2 Materials and methods

2.1 Studied dyes

To investigate the interactions between the solutes (adsorbates) and the adsorbent biomaterial, both a cationic dye (methylene blue) and an anionic dye (Red 141) were analyzed. The distinctive features of each are outlined in Table 1.

Table 1 Properties of the investigated dyes
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2.2 Adsorbent biomaterials

The common cuttlefish (Sepia Officinalis), a cephalopod species with a body length ranging from 20 to 30 cm (including tentacles), possesses an internal structure known as the cuttlebone, which serves a dual function as both an endoskeleton and a mineral reserve.

The cuttlebone (Sepia Officinalis) was obtained from waste material previously washed with distilled water until neutral. Subsequently, it was dried and ground to achieve homogeneous particles with a granulometry of less than or equal to 1 mm. It is noteworthy that the grinding process aimed to produce uniform materials. Ultimately, the material underwent a 24-h drying process at 100 °C, after which it was stored and packaged.

2.2.1 Analysis of cuttlebone by FTIR

Cuttlefish bone (Sepia Officinalis) underwent analysis via Fourier-transform infrared spectroscopy (FTIR) utilizing a Nicolet iS10 Thermo Fisher spectrometer equipped with Attenuated Total Reflection (ATR). The analysis encompassed wavelengths ranging from 525 to 4000 cm−1, featuring a resolution of 2 cm−1, and an averaging of 30 scans.

2.2.2 Mineralogical composition by X-ray diffraction

The identification of crystalline phases was achieved by analyzing the dried powder using a BRUKER D8 ADVANCED X-ray diffractometer. This instrument utilized copper Kα radiation (λ = 1.5406 nm) generated at 50 kV and 20 mA, and the instrument scanned diffraction angles 2θ ranging from 5° to 70°.

2.2.3 Analysis by scanning electron microscopy

The structure of cuttlebone grains were characterized using an XL30 ESEM scanning electron microscope (SEM). Prior to observation, the samples underwent gold-sputtering and were examined at an accelerating voltage of 15 kV.

2.2.4 Monte Carlo and molecular dynamic simulation

MD serves as a potent method for exploring interactions within molecules, with a particular focus on metal-adsorbate interaction [18]. Since the organic dyes Red 141 and Methylene Blue feature numerous active sites capable of interacting with calcium carbonate atoms (110), MD simulations were carried out utilizing the Adsorption Locator model incorporated into the Materials Studio software (version 17.1.0.48) [19]. These simulations utilized appropriate operational parameters, including a simulation box (31.22 × 44.19 × 46.61) employing periodic boundary settings and a vacuum layer (20) containing 210 H2O molecules 9H30+ ions, 9Cl− ions, Red 141, and Methylene Blue. Molecular dynamics simulations aimed to identify the most favorable adsorption conformation characterized by a favorable adsorption energy using the forcite model under NVT ensemble conditions at 298 K, employing an Andersen thermostat [20]. A phase duration of 1 femtosecond, a complete simulation span of 500 picoseconds, and simulated temperatures maintained at 298 K, and the COMPASS II force field were utilized.

3 Results and discussion

3.1 Experimental result

3.1.1 Analysis of cuttlebone by FTIR

FTIR analyses has been carried out as described previously. Figure 1 depict the resulting FTIR spectrum of cuttlebone fish which closely resembles the one reported by Satheeshkumar Balu et al. [19].

Fig. 1
figure 1

FTIR spectra of cuttlebone

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The infrared spectroscopy spectrum of cuttlebone displays three modes of CO extension within the group of carbonate, appearing as a triplet: a wide and strong absorption band at 1459 cm−1, a narrow and intense band at 874 cm−1, and a narrow and weak band at 712 cm−1 [17, 21,22,23]. These bands are accompanied by peaks at 2976 cm−1, 2872 cm−1, 2510 cm−1, and 797 cm−1 [21]. The presence of a hydroxyl groups was verified by the characteristic peak at 3430 cm−1 [24].

3.1.2 Mineralogical composition by X-ray diffraction

XRD is a highly effective method for identifying the crystalline phases present in a material. However, this technique is limited to identifying crystallized phases only. The mineral composition of the cuttlebone was identified through XRD (as shown in Fig. 2). The crystalline phases formed were identified by analyzing the dried powder. Crystallographic identification was accomplished by contrasting the experimental XRD patterns with standards supplied by the Joint Committee on Powder Diffraction Standards (JCPDS), specifically card #96-400-1361 for Calcium carbonate (CaCO3) [16]. Importantly, all identified peaks in the structure were indexed without any additional peaks attributed to undesired phases. The presence of fine and intense peaks suggests a small average crystallite size and excellent crystallinity of the material under investigation.

Fig. 2
figure 2

XRD spectrum of cuttlebone

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3.1.3 Analysis by scanning electron microscopy

The structure of cuttlebone grains was investigated using a XL30 ESEM scanning electron microscope. The image in Fig. 3 depicts the structural morphology of the analyzed substrate. The scanning electron microscope image reveals that the substrate is porous and consists of larger, irregular particles [25]. This observation suggests that cuttlebone is a porous material.

Fig. 3
figure 3

Scanning electron microscopy image of cuttlebone

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3.1.4 Adsorption preliminary study

The adsorption experiments were conducted under static conditions by agitating synthetic colored solutions in the presence of the biomaterial. This research examined the impact of critical factors on adsorption capacity, encompassing the adsorbent mass, pH, contact duration, and initial dye concentration. Langmuir and Freundlich adsorption isotherms were scrutinized to gain detailed understanding of adsorption effectiveness. For assessing the remaining concentration of each dye, a JASCO V-630 UV/visible spectrophotometer was utilized. After centrifugation at 6000 rpm, the absorbance of the treated solution was gauged, and residual dye content was calculated by interpolating with pre-determined calibration curves.

3.1.5 Effect of adsorbent mass on discoloration

Erlenmeyer flasks, each containing 100 mL of colored solution concentrated at 20 mg/L (initial pH 6.6), were used. Various masses of cuttlebone, ranging from 0.1 to 1.8 g, were added to the flasks. The mixtures were stirred at 500 rpm for 2 h, subsequently, the supernatants were examined to ascertain the remaining dye concentration relative to the mass of the added adsorbent. The resulting data are presented in Fig. 4.

Fig. 4
figure 4

The decolorization efficiency of Red 141 and methylene blue relative to the adsorbent mass (C0 = 20 mg/L; pH 6.5; stirring = 500 rpm; V = 100 mL; contact time = 2 h; T = 24 ± 2 °C)

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The graph depicts that the decolorization efficiency increases proportionally with the mass of the biomaterial until decolorization occurs at around 14 g/L, resulting in a decolorization efficiency of 90% for the Red 141 dye and 41% for the Methylene Blue dye. Consequently, the adsorbent doses ranging from 1 to 14 g/L indicate that optimal performance is achieved at an adsorbent dosage of 1.4 g (see Fig. 4). This outcome was anticipated since removal efficiency typically rises with increased adsorbent mass, suggesting that a larger available mass provides more surface area for adsorption. Moreover, higher adsorbent doses in the solution lead to increased availability of exchangeable sites for ions. The escalation in adsorbent dose suggests a higher quantity of adsorption locations on the surface of the adsorbent, indicating the need for a substantial amount of adsorbate to saturate the adsorbent [26,27,28]. These results collectively demonstrate that cuttlebone (Sepia Officinalis) exhibits a strong affinity for the anionic dye Reactive Red 141, while the uptake of the cationic MB dye on the biomaterial remains limited. Consequently, adsorption efficiency relies on both the characteristics of the adsorbate and those of the adsorbent material [29].

3.1.6 Effect of pH on dye removal

Consistently, across all adsorption investigations, pH has emerged as a critical factor due to its potential to influence the structure of both the adsorbent and adsorbate, along with the uptake mechanism. Therefore, comprehending the impact of pH on adsorption effectiveness is paramount. In this study, pH was varied from 3.4 to 11.5 using either a 0.1 N hydrochloric acid solution (HCl) or a 0.1 N sodium hydroxide solution (NaOH). A mass of 1.4 g of cuttlebone was added to 100 mL of the colored solution and stirred. The results, depicted in Fig. 5, reveal that the adsorption of reactive red dye 141 is notably affected in highly basic conditions, possibly due to competition with OH- ions [30, 31]. However, the impact of pH on the adsorption of methylene blue dye remains limited. It is noteworthy that all decolorization tests on cuttlebone were conducted at the normal solution pH (without adjustment) to mitigate potential pH-related effects.

Fig. 5
figure 5

Decolorization yield of aqueous solutions by cuttlebone as a function of pH (m = 1.4 g; V = 100 mL; C0 = 20 mg/L; contact time = 2 h; stirring = 500 rpm; T = 24 ± 2 °C).

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3.1.7 Study of adsorption kinetics

Under the same operational parameters outlined previously, experiments were conducted to explore the uptake kinetics of Reactive Red 141 and MB dyes on cuttlebone. A 100 mL colored solution with a concentration of 20 mg/L was agitated at 500 rpm while containing 1.4 g of the biomaterial under study, with the solution’s pH maintained at its natural level without adjustment (pH 6.5). Samples were collected periodically to evaluate dye removal efficiencies. The outcomes are presented in Fig. 6.

Fig. 6
figure 6

Influence of the duration of contact on the adsorption of dyes (Red 141 and methylene blue) by cuttlebone (C0 = 20 mg/L; m = 1.2 g; pH 6.5; stirring = 500 rpm; V = 100 mL, T = 24 ± 2 °C)

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The kinetic investigation into the removal of the two dyes by cuttlebone reveals that the effectiveness decolorization of Red 141 and MB increases rapidly with prolonged contact time. Generally, equilibrium is attained after 80 min of stirring. Following this duration, the decolorization efficiency of the Red 141 solution reaches 80%, whereas it does not surpass 34% for Methylene Blue. Consistent with the mass-effect study, cuttlebone demonstrates a higher adsorption affinity for the anionic dye Red 141 compared to the cationic dye Methylene Blue. This pattern aligns with findings in the current literature, where swift absorption of dye onto diverse biosorbents takes place during the initial phases of contact time, succeeded by a gradual absorption approach towards equilibrium. [26].

3.1.8 Effect of initial solute concentration

The experiments involved agitating 1.4 g of cuttlebone in colored solutions containing concentrations ranging from 10 to 180 mg/L for 120 min. The experiments were carried out under the solution's ambient pH (pH 6.5), with agitation at 500 rpm and at ambient temperature. Remaining concentrations were measured and subsequently utilized to track the alteration in adsorbed quantity per unit mass, Q (mg/g), in relation to the initial concentration (mg/L) (Fig. 7).

Fig. 7
figure 7

Effect of the initial concentration of the dyes on the discoloration, (pH 6.4; m = 1.2 g; V = 100 mL; contact time = 2 h; stirring = 500 rpm; T = 24 ± 2 °C)

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The results suggest that the adsorption capacity of cuttlebone increases with higher initial concentrations of both dyes. However, a plateau is noted beyond a concentration of 160 mg/L, which is attributed to the saturation of active sites on the adsorbent surface in the presence of high dye content. Furthermore, elevating the initial concentrations of MB ions increases the frequency of collisions between dye ions and the adsorbent, thereby enhancing the adsorption process [32, 33].

3.1.9 Adsorption isotherms

Adsorption isotherms are commonly employed to ascertain the maximum binding capacities of pollutants and discern the type of adsorption. The outcomes, assessed through the Langmuir and Freundlich’s mathematical models, allowed for the determination of both adsorption parameters and the highest adsorption capacity [32, 34,35,36].

Langmuir model:

$$\frac{1}{{Q}_{e}} = \frac{1}{{Q}_{m}} + \frac{1}{{K Q}_{m}{ C}_{e}}$$
(1)

Freundlich model:

$${\text{log}\,Q}_{e }= log{K}_{f}+ \frac{1}{n }\text{log}\,{C}_{e}$$
(2)

with Qe is the equilibrium adsorption capacity (mg/g).

$${Q}_{e }= \frac{{(C}_{0} - {C}_{e}) V}{m}$$
(3)

with: V is the volume of solution (mL), m: mass of the adsorbent (g), C0: initial adsorbate concentration (mg/L), Ce: residual solute concentration at equilibrium (mg/L), Qm: maximum adsorption capacity (mg/g), k: constant of adsorption equilibrium for the solute/adsorbent couple (L/mg), kf and n: distinctive parameters indicating the efficacy of an adsorbent in relation to a specific solute.

The adsorption isotherms were examined by stirring 1.4 g of the adsorbent in colored solutions with concentrations ranging from 10 to 180 mg/L. The interaction between the adsorbent and adsorbate lasted for 2 h, with agitation at 500 rpm. After analyzing the supernatant and determining the remaining concentrations we observed the variation of 1/Qe with 1/Ce according to the Langmuir model and the variation of log Qe with log Ce according to the Freundlich model. The obtained results are depicted in Figs. 8 and 9.

Fig. 8
figure 8

Linearization of the Langmuir equation in the case of the adsorbent/adsorbate systems studied (pH 6.6; V = 100 mL; m = 1.4 g; contact time = 2 h; stirring speed = 500 rpm; T = 24 ± 2 °C)

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Fig. 9
figure 9

Linearization of the Freundlich equation in the case of the adsorbent / adsorbate systems studied (pH 6.5; V = 100 mL; contact time = 2 h; m = 1.4 g, stirring speed = 500 rpm; T = 24 ± 2 °C)

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The line plots obtained from the experimental data of this adsorption process facilitated the determination of the values of the Langmuir and Freundlich constants as well as the equilibrium parameters. These values were calculated using linear regression analysis (Table 2).

Table 2 Adsorption equilibrium parameters according to the Langmuir model and that of Freundlich
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The linear plot of the results (Figs. 8 and 9) reveals that the adsorption of Red 141 on Cuttlebone conforms to the Langmuir model, exhibiting an excellent linear regression coefficient R2 = 0.932, which is very close to unity. This indicates that dye molecules might be adsorbed individually in monolayers without interactions between dye molecules. [33, 35]. Conversely, the adsorption of Methylene Blue on Cuttlebone aligns with the Freundlich isotherm, displaying an excellent linear regression coefficient R2 = 0.948, which is very close to unity. Below, Table 2 exhibits the constants of both isotherms alongside their correlation coefficients, supporting our conclusions. Moreover, the outcomes suggest that Cuttlebone demonstrates superior efficacy in removing the anionic dye Red 141, boasting a peak adsorption capability of 129.87 mg/g compared to the MB cationic dye, which has a maximum adsorption capacity of approximately 23.86 mg/g [37, 38].

3.2 Modeling results

3.2.1 Monte Carlo simulation

Adsorption at the interface between organic molecules and the adsorbent through theoretical modeling methodologies utilizing MD simulation, with consideration given to the surrounding medium [39]. Upon adsorption of Red 141 and Methylene Blue onto the adsorbent, the fluctuation energies and temperature profiles (398 K and 333 K) reach equilibrium, as depicted in Fig. 10. Figures 11 and 12 show the upper and lateral views, respectively, of the adsorption configurations of Red 141 and Methylene Blue on the surface of calcium carbonate in an acidic solution at temperatures of 398 K and 333 K. The presence of Red 141 and MB structures is detected on the surface of the initial calcium carbonate layer, suggesting successful adsorption of the molecules. This effectiveness can be attributed to covalent connections at the Red 141/Methylene Blue –CaCO3 (110) interface, which positively influences the adsorption behavior. This technique enhances surface coverage by adsorbing the investigated heteroatoms and π bonds efficiently. Indeed, these species are effectively adsorbed onto calcium carbonate molecules, supporting the efficacy of studies on water pollution. Simulation results are represented using energy parameters, specifically binding (Ebinding) and interaction (Einteraction) energies.

Fig. 10
figure 10

Stimulation of adsorption structures of Red 141 over Fe (110) surface at 298 K through molecular dynamics

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Fig. 11
figure 11

Stimulation of adsorption structures of Red 141 over Fe (110) surface at 298 K through molecular dynamics

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Fig. 12
figure 12

Stimulation of adsorption structures of MB over Fe(110) surface at 298 K through molecular dynamics

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3.2.2 Molecular dynamic simulation

The parameters values are utilized to compute the degree of adsorption of Red 141/MB and their interaction with the calcium carbonate surface. Negative contact energy confirms the capacity of Red 141/Methylene Blue to contact with the metal [40]. At 398 K, the corresponding interaction energies for Red 141 and Methylene Blue are − 1036.54 kcal/mol and − 478.25 kcal/mol, respectively.

From the information provided in Table 3, it can be deduced that the adsorption energy of Red 141 is notably higher than that of Methylene Blue, validating the superior adsorption of Red 141 compared to Methylene Blue. As depicted in Figs. 11 and 12, and considering their distances from the first surface of calcium carbonate, Red 141 exhibits superior adsorption onto the calcium carbonate surface compared to Methylene Blue. Additionally, it is noteworthy that Methylene Blue is adsorbed in its planar form, which is advantageous as it allows for a higher quantity of adsorption compared to its other forms.

Table 3 Adsorption energies of all used molecules in MC simulation
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For further analysis, let's delve into a detailed explanation of the interaction mechanism of each compound. We have opted to conduct individual experiments for each compound under identical conditions, interacting solely with the calcium carbonate surface.

We have presented the results in Figs. 11 and 12. In the first figure, we reaffirmed that the MB compound adsorbed in its planar form, with a distance of 3.7 Å from the nearest calcium carbonate atom. Simultaneously, Red 141 interacted with the metal through its six sulfonate groups at a distance of 3.4 Å from the calcium carbonate atoms. Based on these findings, we can conclude that these two molecules exhibit distinct interaction mechanisms. MB undergoes adsorption via the physisorption phenomenon, while the adsorption of the second compound follows the chemisorption phenomenon, as indicated by its proximity to calcium carbonate at 3.4 Å [41].

4 Conclusions

This study has demonstrated that Cuttlebone is a highly effective medium for decolorizing aqueous environments contaminated with organic dyes. Several experiments were performed to clarify the binding mechanisms of the two dyes on the examined biomaterial. Overall, the results indicated that Cuttlebone exhibits a stronger adsorption affinity for the Red 141 anionic dye compared to the Methylene Blue cationic dye (MB). The experiments also revealed that variations in pH significantly influence the degree of discoloration, with discolouration rates exceeding 90% for the Red 141 dye and 41% for the Methylene Blue dye. The adsorption isotherms of both dyes by Cuttlebone demonstrated that the adsorption of Red 141 conforms to the Langmuir model, with an excellent linear regression coefficient R2 (0.932). Conversely, the adsorption of Methylene Blue tends to adhere to the Freundlich isotherm, with an excellent linear regression coefficient R2 (0.948). The highest adsorption capacities for Red 141 and Methylene Blue dyes were established as 129.87 mg/g and 23.86 mg/g, respectively. These results imply that Cuttlebone could be a potent and efficient adsorbent for eliminating organic dyes from both aqueous solutions and industrial wastewater. MC and MD modeling additionally corroborated the experimental findings, exhibiting a robust association with the adsorption capability of Red 141 onto the calcium carbonate surface.