In this study, sawdust biochar-O3-TETA (SDBT), a novel biochar, was prepared via treatment with 80% sulfuric acid, followed by oxidation by ozone and subsequent treatment with boiling Triethylenetetramine (TETA). Characterization studies of the prepared SDBT adsorbent were performed with SEM–EDX, BET, XRD, BJH, FT-IR, DTA and TGA analyses. The adsorption efficiency of MB dye by SDBT biochar from water was investigated. Methylene Blue (MB) dye absorption was most effective when the solution pH was 12. The maximum removal % of MB dye was 99.75% using 20 mg/L as starting MB dye concentration and 2.0 g/L SDBT dose. The Qm of the SDBT was 568.16 mg/g. Actual results were fitted to Temkin (TIM), Freundlich (FIM), and Langmuir (LIM) isotherm models. The experimental results for SDBT fitted well with all three models. Error function equations were used to test the results obtained from these isotherm models, which showed that the experimental results fit better with TIM and FIM. Kinetic data ere investigated, and the pseudo-second-order (PSOM) had R2 > 0.99 and was mainly responsible for guiding the absorption rate. The removal mechanism of the MB dye ions in a base medium (pH 12) may be achieved via physical interaction due to electrostatic interaction between the SDBT surface and the positive charge of the MB dye. The results show that SDBT effectively removes the MB dye from the aqueous environment and can be used continually without losing its absorption efficiency.
Introduction
Our world is evolving into new perspectives with the growing population and technological advances. In the current period, water consumption has dramatically increased. Conserving water resources to ensure future water security is more critical now than ever. Households, industry, and agriculture produce large amounts of sewage containing various pollutants. Chemical compounds that place a heavy burden on the ecosystem can be listed as heavy metals1,2,3,4,5, drugs6,7, pesticides8,9,10, hydrocabons11,12 and dyes13,14,15,16,17. Dyes are one of the most critical categories of contamination18. Synthetic dyes are the most commonly used dye type in textile, leather, and many other industries19. Because these dyes are toxic, non-biodegradable and carcinogenic, they provide a grave risk to the environment and public health20,21. The average amount of unprocessed dyes released into water bodies is around (0.7–2.0) × 105 tons per year22. Azo dyes are used too much because they have a wide variety of colors and are the most compatible among all synthetic dyes, creating cancer-causing substances18.
The main methods of treating effluents from dyes factories in the industry can be listed as electrochemical treatment23, chemical oxidation24, biological treatment25, photo-degradation26,27,28,29, coagulation/flocculation30, advanced oxidations31,32,33,34 and adsorption treatment15,16,17,19,35. However, most methods have disadvantages, such as being able to partially remove stubborn and nonbiodegradable dyes, being uneconomical, and creating undesirable by-products. However, among the methods used in dye effluent water treatment, adsorption is much more advantageous than other methods owing to its simplicity of design, affordability, and ease of usage36. However, scientists continue their studies to develop both effective and cheaper adsorbent materials since the production and processing of activated carbon, which is the greatest used adsorption method, is an expensive process3,37,38,39. In this way, biochar obtained from waste products and large mass also prevents the waste of resources. In the literature, biochars are obtained by gasification or pyrolysis of various biomass in an inert gas environment, such as argon or nitrogen, at temperatures higher than 350 °C40. Biochars have more functional groups despite having a lesser surface area and pore capacity than activated carbons41,42.
The efficiency of biochars in wastewater removal is directly associated with the nuber and variety of functional groups that will be included in its structure. This can be attained by making chemical changes to the biochar surface. Carbon surface activation, oxidation, nanoscale formation, and metal impregnation are among the methods used to increase the biochar absorption capacity43. The biochar absorption capacity can be increased by attaching amino groups to the surface41. It is feasible to increase the functional group number by treating biochars with different acids (HNO3, H3PO4 or H2SO4), different bases (H2SO4, NaClO, HNO3, KOH or H3PO4) or oxidizing reagents (KMnO4, NaClO, NH3H2O, H2O2 or (NH4)2 S2O8))42,44,45. It has been observed in many studies that biochars are loaded with nanometals, improving oxidation resistance, increasing the surface area, expanding the adsorption sites and having high thermal stability46. Agents such as FeSO4, H2, NH3H2O, Na2SO3 and aniline are among the most commonly used reducing agents47. There have been many studies on the removl of many pollutants with activated carbons derived from agricultural biomass. Coconut husk48, sesame hull49, olive stone50, green algae Ulva lactuca51, orange peel52, tea waste53, gulmohar54, rice straw55, potato56, Macore fruit57, Barely straw58, red algae Pterocladia capillacea59, mandarin peel60, sugarcane bagasse52, coffee bean husks61, watermelon peel62 and peanut husk63 are some of this agricultural biomass.
Numerous elements, including its high carbon content, aromatic functional groups containing oxygen, and high porosity, may have an impact on its structure. Its surface area, stable molecular structure, and porosity encourage the adsorption of contaminants on it3. According to Fuertes et al.1, in the first 15 min at starting pH 2, direct red 23 and 80 were shown to have adsorption capacities of 10.72 and 21.05 mg/g for biochar made from maize Stover. On the other hand, Wang et al.’s14 investigation focused on the adsorption of harmful metals onto hickory wood-derived biocharthat had been KMnO4-treated. According to their findings, the biochar they produced displayed adsorption capacity 153.1 mg/g of Pb, 34.2 mg/g of Cu, and 28.1 mg/g of Cd. This variation in adsorption might be brought about by these metals’ varying valences and their affinity for the biochar. Additionally, Sun et al.16 observed that increasing the amount of biochar (made from swine manure) from 1 to 8 g/L led to a greater number of active sites that could be used to adsorb methylene blue. When methyl violet initial concentrations ranged from 40 to 816 mg/L, Xu et al.18 used peanut straw biochar and achieved an adsorption capacity of 104.61 mg/g.
Many studies deal with the removal of MB dye through adsorption, but in the author knowledge, the modification of sulphonated SDB biochar by treating SDB with Ozone followed by modification with TETA is used for the first time for MB removal. Therefore, this work evaluated the effectiveness of a novel sawdust biochar-O3-TETA (SDBT) adsorbent forthe adsorption of MB dye from an aqueous solution. This adsorbent is readily available, biodegradable, non-hazardous, and affordable. The impacts of SDBT dosage, pH, beginning adsorbent concentration, and contact duration between SDBT and MB dye were tested as removal conditions for MB dye from an aqueous solution. To study the adsorption structure and maximum adsorption capability of SDBT adsorbent adsorption isotherms were also tested.
Materials and methods
Resources and instrument
In order to make biochar, wood sawdust from a nearby wood market in Alexandria, Egypt, was gathered and utilized as a raw material. Methylene blue dye (Assay 99%) was used to create the standard stock solution; it was purchased from Sigma Aldrich in the USA. This investigation utilized Pg Instrument model T80 UV/Visible High-Performance Double Beam Spectrophotometer, A JS Shaker (JSOS-500), and pH meter JENCO (6173) were utilized. Based on a thermodynamic model, the adsorption–desorption isotherm of SDB, DBO, and SDBT biochars was conducted in N2 environment. N2 adsorption at 77 K was used to determine the surface area (SA) of the SDB, SDBO, and SDBT biochars using a surface area and pore analyzer (BELSORP—Mini II, BEL Japan, Inc.)64,65. Surface area (SBET) (m2/g), monolayer volume (Vm) (cm3 (STP), average pore diameter (MPD) (nm), total pore volume (p/p0) (cm3/g) and energy constant (C) values of SDB, SDBO, and SDBT biochars were calculated using this plot. The mesoporous SA (Smes), microporous SA (Smi), the volume of mesoporous (Vmes), and the volume of microporous (Vmi) of SDB, SDBO, and SDBT biochars were assessed using the Barrett–Joyner–Halenda (BJH) model. The computations were carried by with the BELSORP analysis program software. The BJH method66 was also used to extract the pore size distribution from the desorption isotherm. The form of the biochar’s surface was examined using a scanning electron microscope (SEM) (QUANTA 250). The functional groups on the surface of biocharswere investigated using Fourier Transform Infrared (FTIR) spectroscopy (VERTEX70) coupled with an ATR unit model V-100. On the surface of the SDB, SDBO, and SDBT biochars, IR-observable functional groups were found in the 400–4000 cm–1 wavenumber range with resolution of 0.5 cm–1. The SDT650-Simultaneous Thermal Analyzer instrument was used for thermal analyses with a temperature range of 50–1000 °C and a ramping temperature of 5 °C/min. X-ray diffractograms (XRD) was investigated using a Bruker Meas Srv (D2 PHASER) (D2-208219)/D2-2082019 diffractometer working at 30 kV and 10 mA with a 2θ range of 5–80 and a Cu tube (λ = 1.54).
Methods
Sawdust biochar (SDB) preparation
To remove dust, the collected wood sawdust was thoroughly washed with tap water multiple times. It was then dried for 24 h at 105 °C in an oven. The samples were first cooked in a refluxed system at 280 °C for 4 h with 100 g of sawdust in a 400 mL solution of 80% H2SO42,3,41,42,44, after which, the samples were filtere, washed with distilled water (DW) until the washing solution became neutral, and then washed with EtOH. The weight of the finished biochar product (45 g) was ascertained after oven drying at 105 °C. This process produced biochar which was named SDB.
Preparation of ozonized saw dust biochar (SDBO)
Following preparation, the SDB was treated with ozone in DW. For ozone treatment of SDB, 200 mL of DW was used to ozonate 40 g of produced SDB for 2 h. After filtering, the SDB was then washed with ethanol and DW2,3. The ozonated SDB was oven-dried overnight at 105 °C and branded as SDBO.
Treatment of SDBO with TETA
TETA (100 mL) was used to boil 30 g of SDBO biochar for 4 h, after which it was cooled, filtered, and washed with DW and EtOH. The solid biochar was branded as SDBT after drying for 24 h at 105 °C.
Absorption measurement for methylene blue dye
By dissolving 1.0 g of MB dye in 1000 mL of DW, a stock solution of the dye (1000 mg/L) was created, and this solution was diluted to acieve the necessary concentration for the removal test and the standard curve. To assess the absorption capacity, thermodynamic, and kinetic properties of SDBT, which was created from SDB, batch adsorption experiments were used. A series of Erlenmeyer flasks (300 mL) containing 100 mL of various MB dye solution concentrations and varying doses of biochar were shaken at 200 rpm for a predetermined period. 0.1 M HCl or 0.1 M NaOH was used to change the sample pH to the required values. After separating the adsorbent from around 0.5 mL of the solution in the Erlenmeyer flask, the concentration of MB dye was measured at various intervals and in equilibrium. Spectrophotometry at λmax 665 nm was used to assess the amount of MB dye present67,68. The absorption capacities of MB dye at equilibrium (qe) were considered from Eq. (1):
$$q_e=frac{C_0-C_e}{W} imes V$$ (1)
where qe is the MB dye amount per unit of absorbent at equilibrium (mg/g); C0 and Ce (mg/L) are the starting and equilibrium MBdye concentrations in the liquid phase, respectively; V is the volume of the solution (L), and W is the SDBT mass in gram.
Solution pH impact
With 100 mL of 100 mg/L starting MB dye concentration and solution pH (2–12), the impact of pH on SDBT was examined69.
The impact of the starting MB dye concentration, adsorbent dose, and contact duration
With varying starting MB dye solution concentrations (20–120 mg/L) and various dosages of SDBT biochar (0.05–4.0 g/L), the isotherm investigation for SDBT was carried out. The samples were shaken at 200 rpm, and at various time intervals at room temperature (25 ± 2 °C), the MB dye concentration was determined.
Results and discussion
SDB, SDBO, and SDBT characterization
FTIR estimation of biochar surface functional groups
SDB, SDBO, and SDBT biochars underwent FTIR analysis to identify the functional groups on their surfaces and determine the impact of alteration on the disappearance or emergence of new functional groups. SDB, SDBO, and SDBT bochars’ FTIR spectra are displayed in Fig. 1. While the band at 2938.4 cm–1 shows the C–H stretch of the alkyl in SDB, SDBO, and SDBT biochars, the bands at 3355 and 3213 cm–1 represent the O–H stretching vibration that existed in these biochars. The COOH, C=C, –C–C– stretch (in-ring), and C=O are represented by the bands from 1800 to 1450 cm–1, which are referred to as “overtones”, as band 1697.5 cm–1 in SDB and SDBO70,71. The band at 1028, 1030 and 1035 cm−1 in SDB, SDBO and SDBT, respectively, are correlated to the C–O–H group vibrations72,73,74.
Figure 1
figure 1
FTIR investigation of SDB, SDBO, and SDBT biochars before MB dye absorption.
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After being subjected to MB dye removal for three hours, Fig. 2, displays the FTIR spectrum of MB dye, SDBT, and SDBT biochars. After the biochar under test was subjected to the MB dye absorption method, it was found that all of the FTIR tests showed bands at 1616.2, 1375.1, 1323.1, 1218.9, 1147.5, 1060.7, and 902.7 cm–1 that arerelated to the MB dye. These peaks proved the adsorption of methylene blue onto SDBT biochar51,59,71,72,73,74,75.
Figure 2
figure 2
FTIR investigation of MB dye, SDBT, and SDBT biochars after contacted for 3 h with MB dye.
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SDB, SDBO, and SDBT surfaces area analysis
N2 adsorption–desorption was used to examine how ozone and TETA treatment affected the surface characteristics of wood sawdust biochar (SDB). To determine a particular feature of biochar surfaces, BET and BJH techniques were utilized. The biochars’ BET-specific surface area (SA) declined as SDB (6.61 m2/g) > SDBT (6.08 m2/g) > SDBO (1.98 m2/g), as seen in Fig. 3. It should be highlighted that changes have an impact on a particular surface area and that ozone modification has a more significant impact than chemical modification from TETA therapy. The average pore size shrank in the following order: SDBT (14.514 nm) > SDBO (10.716 nm) > SDB (10.07 nm), and TETA modification had a more significant impact than zone on the reduction in pore size because of the addition of OH groups. SDB, SDBO, and SDBT biochars showed a mesoporous type and have total pore volumes of 16.664 × 10–3, 5.291 × 10–3, and 22.205 × 10–3 cm3/g. BJH results for SDB, SDBO, and SDBT biochars are shown in Fig. 3c, and their surface characteristics are included in Table 1.
Figure 3
figure 3
(a) Adsorption–desorption, (b) BET, (c) BJH investigation of SDB, SDBO and SDBT biochars.
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Table 1 BJH analysis results of SDBO SDB, and SDBT biochars.
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Morphological surface properties of SDB, SDBO, and SDBT
Figure 4 shows the results of a scan electron microscopy (SEM) analysis of the surface morphology of sawdust raw material (RSD), SDB, SDBO, and SDBT biochars. The SDB and SDBO biochars, as illustrated in Fig. 4a,b, look clean and devoid of any impurities or particulates, and no damage to the SDB’s pores due to the dehydration process with 80% H2SO4 was noticed. As a result of ozone surface oxidation,Fig. 4b depicts the SDBO biochar as having a few tiny holes corresponding to the SDBO biochar’s limited surface area. This validates our earlier discovery that ozone treatment of biochar in water resulted in pore blockage, which reduced surface area72,73,74. It is apparent that the ozone treatment in the water caused the pore to be blocked and the surface area of the SDBO biochar to diminish. The shape of the SDBT biochar produced by treating SDBO with TETA under boiling conditions is shown in Fig. 4c. The oxygen and sulfur groups were replaced with amino groups during this process, increasing the surface area of SDBT (6.5051 m2/g) over SDBO (2.1516 m2/g) but still falling short of SDB (7.4265 m2/g). No holes were seen in the RSD’s SEM picture depicted in Fig. 4d.
Figure 4
figure 4
Scan electron microscope investigation of (a) SDB, (b) SDBO, (c) SDBT biochars, and (d) Raw SD material (RSD).
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SDB, SDBO, and SDBT elemental analysis
The chemical makeup of SDB, SDBO, and SBT biochars was examined using an Energy Dispersive X-ray spectrometer (EDX). Table 2 displays the data of the analysis of the elemental percentages of SDB, SDBO, and SDBT biochars and illustrates the lack of nitrogen peak prior to TETA reagent modification. The EDX analysis of SDBT biochar revealed that 13.39% of the sample weight was nitrogen, and 1.18% was sulfur.
Table 2 EDX investigation results of SDB, SDBO and SDBT biochars.
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SDB, SDBO, and SDBT thermal characterization
Figure 5 depicts the TGA breakdown of unprocessed SD, SDB, SDBO, and SDBT biochars. The first stage of breakdown in RSD (Fig. 5a) takes place at temperatures between 50 and 140 °C and involves the loss of moisture and surface-bound water contained in the RSD, with a mass loss of around 9.84%. The second stage involves temperature between 140 and 400 °C with a considerable mass loss of around 65.41% in weight. Temperatures between 400 and 1000 °C are used in the third breakdown stage, with a weightloss of around 9.74%. About 85% of the raw sawdust sample was comprised of the three mass losses. The moisture and surface-bound water contained in the RSD sample were reflected by two significant peaks in the DTA analysis at 55.47 °C, and the substantial weight loss was indicated by a high peak at 363.62 °C (Fig. 5a). With a weight loss of around 14.30%, the first stage of breakdown takes place in the SDB biochar sample (Fig. 5b) at temperatures between 50 and 140 °C. The second phase involves temperatures between 140 and 175 °C and a weight loss of about 2.19%. Temperatures between 175 to 300 °C are used in the third breakdown stage, with a weight loss of around 9.61%. Temperatures between 300 and 1000 °C are used in the fourth breakdown process, with an estimated weight loss of 30.69% (Fig. 5b). The moisture and surface-bound water contained in the sample were represented by four significant peaks in the DTA analysis of the SDB sample at 76.22 °C, and a tiny peak representing a modet weight loss was seen at 163.09 °C (Fig. 5b). The third and fourth peaks occurred at 219.31 and 432.62 °C represented 41.21% mass loss of the SDB sample. The SDBO biochar sample analysis shows three weight loss positions with total mass loss representing 52.09% of the sample mass (Fig. 5c). At temperatures between 50 and 175 °C, the first breakdown stage takes place and results in a weight loss of around 12.26%. 8.18% of the weight was lost in the second stage at temperatures between 175 and 300 °C, while 31.65% was lost in the third decomposition process at temperatures between 300 and 1000 °C (Fig. 5c). The DTA analysis of SDBO sample represented three major peaks at 102.99 °C for moisture and surface-bound water existing in the sample and at 246.08 °C as a moderate peak represented a small weight loss and the third peak was presented at 443.57 °C showing the major mass loss percent (Fig. 5c). The analysis of SDBT biochar sample shows three weight losses positions with total mass los represented 51.619% of the sample mass, which is almost similar to the total mass loss occurred for SDBO sample (Fig. 5d). In the first stage of mass loss, which takes place between 50 and 180 °C, there is an average weight loss of 10.86%. The second mass loss phase occurred at temperatures between 180 and 260 °C, with a modest mass loss of 4.73%. In comparison, the third mass loss step took place at temperatures between 260 and 1000 °C, with a roughly 36.02% weight loss (Fig. 5d). The DTA analysis of SDBT sample represented three distinguish peaks at 99.47 °C for moisture and surface-bound water present in the SDBT sample and at 231.49 °C as a small peak represented a 4.73% mass loss and the third peak was presented at 380.00 °C showing the major mass loss percent (Fig. 5c).
Figure 5
figure 5
TGA investigation of (a) RSD material, (b) SDB, (c) SDBO, and (d) SDBT biochars.
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XRD characterization of SDB, SDBO, and SDBT
Figure 6 displays the SDB, SDBO, and SDBT biochars XRD. Indicating an amorphous carbon structure with aromatic sheets that are arbitrarily aligned, the wide peak in the area of 2Ɵ = 10–30 is indexed as C (002) diffraction peak. In contrast to SDBO, which only has one sharp peak, SDB has two peaks around 2Ɵ = 43.682 and 27.004, whereas SDBO has three peaks altogether. On the other hand, the structure of the SDBT biochar sample has two prominent peaks around the values of 2Ɵ = 25.875 and 43.669, which could indicate various inorganic components mostly made of quartz and albite 75,76.
Figure 6
figure 6
XRD analysis of prepared SDB, SDBO, and SDBT biochars.
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Adsorption of MB dye on SDBT
The removal of MB dye by SDB, SDBO, and SDBT was tested to select which biochar has the highest tendency to absorb MB dye from water. Figure 7 shows the removal test of MB dye using prepared SDB, SDBO, and SDBT biochars. As seen from Fig. 7, SDB and SDBO showed a very low removal % for MB dye, while the aminated biochar SDBT showed a high bility to absorb MB dye from its water solution.
Figure 7
figure 7
Test of MB dye removal by SDB, SDBO, and SDBT biochars (MB dye C0: 120 mg/L and 2.0 g/L biochar dose at room temperature.
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pHPZC and ımpact of pH
The initial pH of the solution was plotted against the difference between the initial and equilibrium pH (Fig. 8a). The pHPZC value for SDBT crossed the x-axis at two points. The pHPZC values for SDBT were 3.0 and 7.7, which are in the acidic and basic ranges. To predict the adsorption process, the pH is a vital operational parameter that affects the surface charges of the SDBT as well as interfacial transport phenomena. The solution pH influences the absorption process by considerably impacting the amino, hydroxyl, and carboxyl groups on the biochar surface. The functional groups on the biochar surface can affect the occurrence of two pHPZC. If the concentrations of these surface functional groups are high enough and their dissociation constants are sufficienly different, biochar with multiple surface functional groups such as carboxylic acids (–COOH) and hydroxyl groups (–OH) or primary amines (–NH2), secondary amines (–NHR) and hydroxyl groups (–OH) can potentially display two pHPZC. Due to the pore structure of the biochar, the total surface charge of the material may fluctuate depending on how accessible the surface functional groups are to ions in solution. Biochar with a lot of micropores may have a more negatively charged surface as a result of more surface functional groups, which might result in a lower pHPZC. In contrast, biochar with a high percentage of macropores may have a surface that is less negatively charged due to the absence of as many surface functional groups, which might result in a higher pHPZC.
Figure 8
figure 8
(a) pHZPC of SDBT (3.0 and 7.7), (b) Inpact of pH on the MB dye removal % by SDBT (MB = 20 mg/L, adsorbent dose = 0.5 g/L, Temperature = 25 °C).
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Methylene Blue (MB) dye removal on SDBT adsrbent, equilibrium studies and adsorbed quantification were performed in a 20 mg/L initial MB dye solution at a concentration of 0.5 g/L of SDBT at 25 °C. For 180 min, pH values between 2 and 12 were used to examine the MB dye’s ability to bind. The pH-dependent variation of MB dye removal % is shown in Fig. 8b. Figure 8b shows that 95.96% of the MB dye is removed when the pH is 12. It can be observed that when the solution pH rose from 2 to 8, MB removal increased from 8.40 to 34.34%, dropped significantly at pH 10, and then increased to its highest level at pH 12. Jabar et al.16 studied the Methylene Blue dye removal using biochar made from African almond (Terminalia catappa L.) leaves and found that the adsorption capacity increased with increasing the solution pH from 2 to 8. This study was one of the literature studies on the removal of azo dyes. In their examination into the removal of the dye Methylene Blue using Bioadsorbent generated from Schinus molle, Razzak et al.77 found tat raising the pH of the solution from 2 to 8 raised the adsorption percentage from 30 to 100%. The literature on Methylene Blue removal has revealed several comparable findings78,79. The ideal pH for SDBT’s elimination of MB dye was 12.
The carboxyl (–COOH), amino (–NH2), and hydroxyl (–OH) functional groups on the biochar surface are extremely sensitive to the pH of the wastewater because it influences the attraction and repulsion forces that exist between the adsorbate and the adsorbent. When the pH of an aqueous solution is low, the water ionizes, depositing H3O+ on the SDBT’s surface-active sites to positively charge the surface. Due to electrostatic repulsion, cationic-charged MB dye molecules cannot bind to the cationic-charged SDBT surface. So, color removal is only partially effective. The protonation of active sites on the SDBT surface relaxes as the pH of the solution rises, making it simpler for the MB dye to transfer from the aqueous solution to the surface of SDBT. The dcrease in competition between H3O+ and the MB cationic dye molecules for adsorption to active sites on the adsorbent surface might account for the rise in adsorption effectiveness with rising pH. Additionally, the evolution of electrostatic interactions between cationic MB dye molecules and anionic SDBT active sites, which occurred as a result of the reappearance of –CO–, –OH–, and –NH– functional groups with rising pH values, may have contributed to the rise in adsorption efficacy.
Contact time impact
Contact time with SDBT is a significant factor in the absorption of MB dye, and for this purpose, this effect was investigated at starting MB dye concentration of 20–120 mg/L by adjusting the solution pH to 12. The MB dye adsorption to SDBT adsorbent was very fast in the first 5 min as seen in Fig. 9, and then a steady increase continued. In the first half hour, 86–97% of the total adsorption was completed. With increasing contact time, the MB dye was continuously removed. Depending on he starting MB dye concentration (20, 40, 60, 80, 100, and 120 mg/L), the elimination at 180 min was 99.75, 99.12, 99.98, 97.08, 98, 84 and 98.84%, respectively.
Figure 9
figure 9
Rremoval of MB dye for 180 min using SDBT as an adsorbent (MB dye C0 = 20–120 mg/L), SDBT dose = 2 g/L, Temperature = 25 °C).
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In cases where the solution concentration is low (20–40 mg/L), the removal efficiency is high since MB dye molecules will easily find empty active sites on the SDBT surface and adhere to them. In the opposite case, since there are too many dye molecules at high concentrations (100–120 mg/L) MB dye, each of them will not find enough empty active sites, and there will be limited removal. A comparable results were found by El Nemr et al.62 and Eleryan et al.15 when they investigated Acid Yellow 11 dye removal by different adsorbents.
Impact of starting MB dye concentration
It is possible to estimate how the initial concentration of the MB dye will impact the equilibriumadsorption capacity (qe) by using the beginning concentration of the adsorbed material, which is a crucial component of the absorption process. The initial MB dye concentration (20–120 mg/L) and adsorbent concentration (0.5–4.0 g/L) were altered to 25 °C and a pH of 12 in order to ascertain the impacts of SDBT dosage on equilibrium adsorption capacity (qe). The steady-state quantity of MB dye adsorbed (qe) for the same starting MB dye concentration rises as SDBT doses are lowered, as shown in Fig. 10. The equilibrium adsorption capacities (qe) in the removal of MB dye were calculated using SDBT adsorbents at various dosages (0.5–4.0 g/L), as shown in Fig. 10. These results range from 4.98 to 38.26, 9.97 to 62.30, 14.91 to 83.14, 19.85 to 90.70, 24.81 to 104.75, and 29.80 to 120.60 mg/g, respectively, for beginning MB dye concentrations (20, 40, 60, 80, 100, and 120 mg/L). As shown in Fig. 10, solutions with greater initial MB dye concentrations have a higher equilibrium adsorption capaity (qe) of MB dye on SDBT. As the adsorbent dosage rose, it was seen to decline. The initial concentration of the MB dyes had an impact on how efficiently they were absorbed from their aqueous solution, as seen in Fig. 10. In their research on the elimination of the dye Acid Yellow 11, El Nemr et al.80 noticed a similar pattern in their findings. The boundary layer effect is the first thing that happens to the MB dye molecules as they adhere to the SDBT surface. They diffuse from the boundary layer film to the surface, eventually mixing due to the adsorbent’s porous composition.
Figure 10
figure 10
The effect of MB dye starting concentration (20–120 mg/L) using SDBT doses (0.5–4.0 g/L) on qe (mg/g) at (Temperature = 25 °C).
