Color Adsorption Performance of Bone Biocomponent for Textile Dyeing Effluent Treatment in Ethiopia

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Introduction
Te recent textile coloration practices had been using 700 kilotons of synthetic dyes per year worldwide. Worldwide, about 200 kilotons of dyes are lost to efuents every year [1][2][3]. Azo dyes are the largest category of synthetic colorants and the most often discharged synthetic dye into the environment, accounting for over 70% of all dyestufs used globally. An Ethiopian textile industry statistic shows the country imports over 700 tons of dyestufs [4], of which about 70% from total amount are azo dyes. Azo dyes contain about 10-100 mg/L of hazardous compounds such as oncogenic amines [5] and other chemical pollutants in the form of toxic metals, pentachlorophenol, biocides, and chlorine. It also has toxic efects on aquatic fora and fauna, resulting in severe environmental issues across the globe. Additionally, azo dyes have negative efects on biological oxygen demand (BOD), chemical oxygen demand (COD), and total suspension solids (TSS) [6][7][8]. Most of the dyes are released into the environment without efective wastewater treatment [9]. Te reason may be due to noneconomical wastewater treatment for developing countries such as Ethiopia [10][11][12].
As far as we know, there are limited works on absorbers able to simultaneously remove the color and other contaminants from dye types used for the current experiment. Te biocomponent from the bone is proposed for reducing coloring material and organic ions in industrial wastewater. Terefore, this study aims to analyze the likelihood of using an animal bone biocomponent, CNP, as an efective adsorbent of color and organic molecules from the DR1D and RB109D efuents. Until now, there has been no work on such DR1D and RB109D efuent discoloration using calcium sources.

Materials.
Te fresh raw bovine bones were collected from a local restaurant (Bahir Dar, Ethiopia), whereas the dried bones of bovine were found in a local home ( Figure 1). Other materials were from wet processing laboratories at the Ethiopian Institute of Textile and Fashion Technology (EiTEX), Bahir Dar University.
Industry efuent was collected from Bahir Dar Textile Share Company (BTSC).

Extraction and Preservation of Calcium-Phosphate
Nanopowder. Te recipes for extracting of biocomponents were already studied [68,69]. Te fresh bone was treated with distilled water at 60°C to detach the meat from the bone surface and crushed into small pieces as shown in Figure 1. Ten, 50 gm of crushed bone was boiled to 100°C with 1 M HCl (8.3 ml HCL added into 100 ml distilled water). Te bone was dissolved and then the acidic biocomponent solution was fltered using a micromesh flter. Te fltered acidic solution was treated with various concentrations of NH 3 (ammonia) to form a precipitate of the biocomponent. Te precipitates were collected in a petridish and placed in an oven dryer at a temperature of 100°C for the duration of 10 minutes to evaporate the water. After cooling, the dried biocomponent was ground to form CNP.

Experimental Design.
Te experimental design has been made using the state-ease scientifc tool (Stat-Ease Design Expert 11.1.2.0). Te details for the experimental design of extraction were shown in Table 2. Te design for the percentage discoloration potential of the CNP against DR1D and RB109D efuents was made with two repeats, 12 runs were used for each experiment as shown in Tables 3 and 4.

Yield of Precipitate.
Te yield [70] of CNP was analyzed as per the following equation: where Bi and Bf are initial and fnal weight of bone, respectively.

Response Optimization.
Te response surface methodology (RSM) was used to determine the best independent variable values in order to maximize the response [71]. Te models used were quadratic and two-factor interaction (2FI) in the case of RB109D and DR1D parameters, respectively. Te precipitate optimization goals were maximizing the extract and precipitate whereas the pH was kept in range. It also allows the user to look at how the individual variables interact, making it more efective than the more common single-parameter optimization method. Tese factors have led to the use of RSM in the extraction of biocomponents and percentage color removal in the current case.

Fourier-Transform Infrared Spectroscopy Analysis (FTIR).
Te composition of the biocomponent was analyzed by a Fourier transform infrared spectrophotometer (Perkin Elmer, UATR TWO, Ethiopia), calibrated according to the manufacturer's instructions in the Ethiopian institute of textile and fashion technology (EITEX) lab. After pressing the samples into pellets, the absorption spectra were examined within the wave range from 500 cm −1 to 3500 cm −1 .

Dye Efuent Sampling.
Te dye efuent samples were prepared by mixing synthetic wastewater with dye solutions. Te synthetic wastewater was prepared as per the recipe mentioned by [72] with some modifcations. Te dye solutions were prepared using DR1D and RB109D in distilled water with a concentration of 50 mg/l for each dye solution ( Figure 2). Industrial wastewater was taken from BTSC for comparison with TS after treatment.    Te spectra were examined within the wave range from 400 cm −1 to 900 cm −1 . Te results were used for analysis to determine the adsorption isotherms and efects of treatment duration, as well. Te percentage removal [56,73] was calculated by equation (2), where the percentage values were from UV spectrophotometers [35].

UV Spectrophotometer and Removal
where Abs 0 represents absorbance value before adsorption and Abs represents absorbance value after adsorption.

Equilibrium Adsorption Isotherm.
Te studies were carried out to investigate the adsorption efectiveness of both the efuents. Between 0.5 and 5 grams of the adsorbent were used in the studies and they were placed in 100 mL of the dyes (variable concentration) aqueous solution in conical fasks that were 250 mL in size and were paraflm-sealed. A UV-VIS spectrophotometer was used to measure the solution's residual dye concentration after 60 minutes at 610 nm for RB109D and 490 nm for DR1D, respectively. At a pH of 7, each experiment was carried out three times. Te removal of the dye can be used to explain the adsorption of the dye [74].

BOD, COD, and TSs Analysis.
Te experiments on biological oxygen demand (COD), biological oxygen demand (BOD), and total solids (TSs) were conducted in the laboratory of the Bahir Dar Textile Share Company (BTSC). Tree categories of samples: RB109D, DR1D, and BTSC samples were used at this stage. Te third sample was taken directly from the BTSC industry waste tank to compare with samples from the experiment. Te BOD test was made to determine the amount of oxygen bacteria consumed in a particular volume of water over a given time. Since the treated water is intended for the environment, its organic matter content should be analyzed. A liter of wastewater was used. All the samples were combined for 30 to 45 minutes and stored in dark for fve days. Te BOD measurement was conducted at a temperature of 20°C. Te COD treatment medium was examined using a Lovibond thermos-reactor (Termoreactor RD 125, EiTEX, Ethiopia). A 12 liter more of wastewater was added to the installation. Te samples were stored inside the reactor for two weeks at a temperature of 25°C with constant aeration. At the start and end of the experiment, COD values were measured, and the outcome was presented as a percentage reduction of molecules. Te COD analysis was performed in accordance with SR ISO 6060.

Biocomponent Extraction and Characterization
3.1.1. Bone Biocomponent Extraction. Te result has been calculated, and the average yield of precipitate was 10.57444 g, which is 92.68167 percent. Te dissolved biocomponent was generated by treating waste bone with dilute HCl (0.5 M) as shown in Figures 3(a) and 2(b). Te contribution of HCl acid during extraction is in order to breakdown the complicated component of bone hydroxyapatite into mineral ions in the bone, such as calcium ions and hydrophosphate ions. Te possible reaction that takes place is shown in equations (3)-(6).
Te addition of ammonium to the solution causes the agglomeration of the mineral ions (equation (7)) in the form of a precipitate, as shown in Figures 3(c) and 3(d). A random ammonium addition results in large precipitate agglomerates of calcium phosphate, whereas a slow addition results in fne precipitates. Exposing the precipitate in an oven at 100°C for 10 minutes causes simple dehydration of the water molecules, which occurs either when two hydrogen atoms from one molecule join with an oxygen atom on the other molecule or when a hydroxyl group from one molecule Journal of Engineering reacts with a hydrogen atom from the other molecule. Next, collect the powder from the Petri dish and crush it into a nanosize powder. Te matured mineral matrix is present in a nanosized form as CNP, which is hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) as a reaction potential [75][76][77].

Efect of Biocomponent Solution on Yield.
At constant pH, increasing the concentration of the biocomponent solution (extract) caused a slight increase in the mass of the biocomponent precipitate ( Figure 4). Te reason might be that the more the extract, the more H 2 PO 4 − molecules there are, which could dissociate until the electrolyte saturates. Furthermore, increasing the solution may not have a signifcant efect. Figure 4, there is a signifcant increase in the mass of the CNP biocomponent precipitate when the pH rises due to the addition of ammonia. Te pH of the acidic biocomponent solution was slowly increased as ammonia was slowly added, and then the amount of precipitate that formed also increased. Later, when all of the hydrochloric acids had been neutralized by ammonia, the pH reached seven, after which the pH would increase further as the solution became alkaline, the pH of which would depend on the concentration of ammonia in the solution. However, for our case, we were focused on neutral pH, which is ecofriendly to release the water into the environment after treatment.

Efect of Ammonia on Yield of the CNP. As shown in
Te formation of the precipitate is caused by the dissociation of the ionic molecule H 2 PO 4 by ammonia, as shown in equation (7). Te chemistry is that the tendency of H 2 PO 4 to dissociate is greater than its tendency to hydrolyze, so that the (NH 4 ) 2 (HPO 4 ) exists in crystal form since it is insoluble in water at room temperature. On the other hand, ammonium dihydrogen phosphate can stay dissolved in water [77,78].
3.1.4. Optimum CNP. Te conditions delivering the maximum precipitate of the biocomponent (CaNP) were determined ( Figure 5). Te ideal extraction parameters were 10 ml of the extract with a pH of 6.9. Te mass of the total precipitate yield was estimated to be 13.2664 g under optimal circumstances, which is very similar to the actual value of 13.5 g discovered under the modifed conditions (Table 5) with 89.9% desirability. Tese outcomes demonstrate the model can forecast the experimental conditions. Te neutral pH is recommended because it allows the treated water to be released into the environment with the least pollution. Technically, it is economical to remove a large volume of color from the efuent using a lowmass CNP.

Te Analysis of FTIR.
Te FTIR spectrum of CNP extracted from the animal bone heated at 100 is shown in Figure 6. Te main indication of CNP can be identifed by the characteristic peaks of the phosphate band within two spectral regions: from 844 cm −1 up to 1038 cm −1 and 1320 cm −1 to 1500 cm −1 . All spectral bands of phosphate, especially the two high-intensity phosphate peaks at 1008 cm −1 and 1337 cm −1 demonstrate the isolated CNP adsorbent has a higher phosphate concentration. Tey also represent the presence of tricalcium phosphate. Te spectra also identifed the carbonate bands at 1106 cm −1 , 1566 cm −1 , and 1638 cm −1 , and low intensity of organic carbon vibrations were observed within the region from 1833 cm −1 to 2106 cm −1 . In between bands of 2851 cm −1 and 2918 cm −1 , amide ion stretching was also observed [79][80][81]. Terefore, phosphates, carbonates, and amide ions were incorporated into the CNP.   As shown in Figure 7 and Table 3, an increase of the RB109D efuent concentration from 10 ml to 25 ml caused a lowering of color removal percentage from 97% to 92.5%. Te extract also shows a similar efect, decreasing the percentage of color removal as its concentration increases. Terefore, the addition of more extract into the solution cannot improve the efciency of treatment, which contradicts the efect analyzed by other adsorbents [82]. Te possible reason for such an efect might be due to the inundation of calcium phosphate. Te inundation indicates that there were no unoccupied binding sites available (all active sites of the extract linked with bonds from the dye) for the adsorption of the dye molecules [83].

Color Removal Analysis
Te adsorption might happen for two reasons. Te frst reason is due to the surface calcium chelating with bidentate from functional groups -NH-and C�O, --OH and C�O, -N-and -OH. Calcination was taken place at the boiling temperature of the water, which allowed to get calcium ions within the adsorbent. Previous studies showed no calcium after calcinating a raw bone at a temperature of 1000°C. Whereas, Figure 8 depicts the link between azo-nitrogen and hydroxyl groups in hydroxyapatite and -NH-or ionized carbonyl oxygen in the dye molecule [84].

Efect of DR1D Efuent Concentration on Percentage Color
Removal. Te value of the coefcient of determination (R2) was 0.8259. Such values indicated about 82.59% of variability and could be explained by the selected models. Moreover, the adjusted R2 value of 0.6808 denoted the validity of the quadratic model.
Te interaction efects of DR1D efuent concentration and the extract were investigated for a duration of 90 min in the response plot and contour lines ( Figure 9 and Table 4). A communal rise in the ratio of dye efuent concentration and extract from 9.2 : 5 (ml) to 17.5 : 7.5 (ml), respectively, caused a decline in the efciency of the percentage color removal from 95.5% to 85%. Ten, the decolorization efciency ascends again from 85% to 98% when the ratio continues to rise until 25.5 : 10 (ml). Te reason for such an efect can be a higher concentration of dye efuent as compared to extract; it may cause the saturation of the accessible binding sites on the surface of calcium phosphate [82,85].
Saturation is enhanced as per the slowing of difusion. It is known that the difusion mechanism of DR1D particles into the adsorbent has two steps [86]. Te frst is the dye transfer from the solution to the adsorbent. Te dye diffusion from the adsorbent's surface to the pore is the latter. Due to the very low adsorbate concentration in the solution, intraparticle difusion reduces in the fnal equilibrium stage.

Efect of Extracted Adsorbent on Percentage Color
Removal. As illustrated in Figure 7, the percentage of color removal decreased as we kept increasing the concentration of extracted adsorbent to 10 ml in the case of RB19D efuent treatment. Whereas, in the case of DR1D efuent treatment, the percentage color removal showed a parabolic efect as indicated in Figure 9. It was demonstrated that the azo group is disrupted and a diazo compound and a quinone are formed when azo dyes are oxidized in aqueous media with a calcium phosphate reagent. Tese, then, continue to break down, yielding phenol and nitrogen, respectively (in acidic media). Te pH of the adsorbent was mandatory for   decolorization by biosorption because it attracts charged dyes to the surface of the adsorbent. An increase in the concentration of H + ions (acidic) attracts anionic colors to the adsorbent surface via electrostatic attraction, whereas an increase in the concentration of OH + ions (basic) attracts the dye ions to the biomass surface via electrostatic attraction [87]. Because the concentration of H + ions in the solution might afect both adsorbed molecules and adsorbent particle functional groups, they participate in the molecular adsorption process at the adsorbent's active sites.
At basic pH, the repellent electrostatic interactions between the adsorbent negatively charged surface and the anionic dye abundant prevent the quantity of adsorbed dye molecules from reducing. Te ionization of the dye's amine and amide groups with H + , which renders the dye molecules positively charged, can reduce adsorption below pH of three. As a result, adsorption was decreased [88].

Efect of the Contact Time on Color
Removal. Te efect of adsorbent contact time on color removal was analyzed using the UV-Vis spectrum as shown in Figures 10 and 11. It was observed that all samples of RB109D efuent showned a typical peak in their UV-Vis spectrum at its absorption wavelength of 610 nm. More than 75% of the efuent color reduction has been achieved after one-hour treatment ( Figure 10). Ten, the percentage of color removal gradually increased, and the maximum potential of the adsorbent to remove the color is achieved at 140 min. Te maximum color removal of 96% was achieved for RB109D. Te discoloration was caused due to the breakdown of the azo linkage (colorbearing group) after the dye adsorbed on the surface of the adsorbent. Te degradation chemistry occurs in two phases at the azo (N�N) linkage. First, two electrons are transferred to the azo dye, which acts as a fnal electron acceptor, resulting in dye decolorization and the formation of colorless solutions at each stage. Ten, intermediate metabolites (such as benzene amines) are then eliminated either aerobically or anaerobically [39].
Whereas, the DR1D efuent had no signifcant peak in its UV-Vis spectrum at its absorption wavelength of 490 nm ( Figure 11). It was demonstrated that the extension of treatment time after the frst 20 minutes has less efect on adsorption. More than 75% of the efuent's color reduction was achieved at 20 minutes of treatment time, as shown in Figure 10. After the frst 20 minutes, there was a very slow increase in the percentage of color removal, and the maximum potential of the adsorbent to remove the color was achieved at 140 minutes. Te maximum color removal of 98.65% was achieved for DR1D. Te dye had a faster diffusion rate than RB109D to the adsorbate surface. As a result, the equilibrium period for dye adsorption on the CNP biocomponent was 140 min.
Te rate of the dye adsorption was quicker in the early stages because of the huge concentration diferential between the dye and the adsorbent active sites. Te delayed difusion of the dye into the bulk of the adsorbent is likely to blame for the slower adsorption rate in the latter stages of dye adsorption [89].

Adsorption Isotherm Models.
Adsorption isotherms were illustrated for the dye adsorbed by the unit mass of the adsorbent at room temperature and the concentration of the dye in the solution at a nearly neutral pH [90,91]. Te Langmuir and Freundlich isotherms are the most utilized equations for dilutions that indicate a connection between the equilibrium values. Te Langmuir isotherm was expressed as follows [92]: where K � Langmuir equilibrium constant, Ce � aqueous concentration, Ae � amount adsorbed, and Am � the maximum adsorption capacity of the adsorbent. Te Freundlich equation was written as follows [92]: 98.65% where Kf and n are Freundlich coefcients. Kf and 1/n are correlated to the sorption capacity and intensity of the system. As shown in Figure 12, the RB19D adsorption exhibited the Langmuir isotherm of monolayer adsorption. It was demonstrated that the maximum adsorption capacity was 6.5 milligrams of dye per milligram of adsorbent. Tey were thought to adsorb at a small number of specifc locations inside the calcium phosphate. On the other hand, DR1D exhibited Freundlich isotherms ( Figure 12) of having more than one layer. Te DR1D was shown to have a maximum adsorption capacity of 5.8 milligrams of dye per milligram of adsorbent.
4.6. COD, BOD, and TSS Analysis. Te total COD measured before treatment was 2570, 2500, and 2370 ppm in the RB109D, DR1D, and BTSC efuents, respectively (Table 6). Tose values confrmed that organic and inorganic materials are hazardous to health, so the wastewater must be treated. After treatment with CNP adsorbent, the COD values of the three categories of samples decreased by 82%, 87%, and 70%, respectively ( Figure 13). When administered a synthetic coagulant, as described by [93] and [94], we achieved a removal rate of 55.2%, which is better than the current treatment. Besides environmental hazards, azo dyes are very toxic because of the reduction and breakdown of the azo bonds to produce toxic aromatic amines. Aromatic amines oxidize because of the direct oxidation of the azo bond, linking them to very reactive electrophilic diazonium salts and azo dyes [95]. Since each pathway could be compoundspecifc, azo toxicity is most likely brought on by several mechanisms. Te azo dyes' altered intermediates have been shown to be very poisonous and mutagenic.
Te fndings before treatment show that the BOD values for RB109D, DR1D, and BTSC were 6200 ppm, 4515 ppm, and 4460 mg/L, respectively (Table 6). After treatment, the BOD values for RB109D, DR1D, and BTSC were 89, 90, and 89%, respectively ( Figure 13). Compared to the current study, others reported reducing the BOD of textile efuent to 51.4% [94] and 82% [96] using synthetic coagulant. So, the current treatment is efective.          Ae (mg dye/ltr) Figure 12: Raw data and exponentially ftted adsorption isotherm plots of Freundlich (DR1D dye) and Langmuir (RB19D dye), where x � Qe (mg dye/mg adsorbent) and y � Ae (mg dye/ltr of aqueous). Before the treatment, TSS for RB109D, DR1D, and BTSC were 6200, 4515, and 4460 mg/L, respectively ( Table 6). Te result shows a large amount of pollution is caused due to the textile wastewater which is also determined by other researchers [97]. After treatment, the TSS value of the treated samples exhibited remarkable results having TSS percentage removal of 82%, 89%, and 71%, respectively ( Figure 13).

Conclusion
Animal bone wastes are being used as a substitute adsorbent in the current study to treat textiles dye efuent. Te CNP biocomponent precipitate, which included calcium and phosphate ions, was used to treat RB109D and DR1D effuents. Te molecular composition of the extracted adsorbent was analyzed by FTIR, showing spectral peaks of calcium and phosphate chelates. Te CNP biocomponent from animal bones can adsorb color from aqueous RB109D and DR1D efuents in one hour. UV-Vis analyses were made to analyze how fast the color removal and other residues took place. Te chemistry of discoloration was caused by the reductive breaking of azo bonds (-N�N-) with reductive oxygen. Te adsorption pattern shows the Langmuir isotherm in the case of RB109D efuent. On the other hand, DR1D exhibited Freundlich isotherms. Te average color removal of 92.68% and 95.66% was achieved for RB109D and DR1D, respectively. Te extracted adsorbent and efuent water concentration showed an upward parabolic efect on the percentage of color removal from the DR1D efuent, whereas in the case of RB109D, both the extracted adsorbent and efuent water concentration showed a negative correlation with the percentage of color removal. Terefore, the adsorbent was shown to be significant in removing the coloring matter from both dye types.
For industrial uses, our team has been focusing on the chemical-free extraction of the CNP biocomponent. As a future work, the reuse of the treated water, sludge for composite application, and regeneration of the calcium phosphate after treatment needs experimentation.

Data Availability
Te experimental data used to support the fndings of this study are included within the article.