The most challenging mission in wastewater treatment plants is the removal of anionic dyes, because they are water-soluble and produce very shining colours in the water. In this regard, kenaf core fiber (KCF) was chemically modified by the quaternized agent (3-chloro-2-hydroxypropyl)trimethylammonium chloride to increase surface area and change the surface properties in order to improve the removing reactive anionic dyes from binary aqueous solution. The influencing operating factors like dye concentration, pH, adsorbent dosage, and contact time were examined in a batch mode. The results indicate that the percentage of removal of Reactive Red-RB (RR-RB) and Reactive Black-5 (RB-5) dyes from binary solution was increased with increasing dyes concentrations and the maximum percentage of removal reached up to 98.4% and 99.9% for RR-RB and RB-5, respectively. Studies on effect of pH showed that the adsorption was not significantly influenced by pH. The equilibrium analyses explain that, in spite of the extended Langmuir model failure to describe the data in the binary system, it is better than the Jain and Snoeyink model in describing the adsorption behavior of binary dyes onto QKCF. Also, the pseudo-second-order model was better to represent the adsorption kinetics for RR-RB and RB-5 dyes on QKCF.
Environmental pollution due to speedy development of industries causes harmful effect on human health and ecosystem. The textile dyeing industries have generated a massive pollution problem because it is considered one of the most industries which used a wide range of dyes in their production. Consequently, it is the most polluting water sources [
It is estimated that every year 280,000 tones of textile dyes are released in textile mill effluent [
Although the colour is not included in the Environment Conservation Rules which was published in 1997, it is an issue in dye effluent because, unlike other pollutants, it is so visible. Consequently, international textile industries are increasingly setting discharge standards for colour [
The use of commercial activated carbon for removing dyes is expensive as it is obtained from nonrenewable starting materials like lignite, coal, and petroleum coke. Therefore, aqueous phase adsorption by utilizing different types of agroresidues is one of the most alternatives materials for removing different types of dyes (including reactive dyes) from wastewater [
Agricultural biomass can be procured either directly from plant species or indirectly from a processing of domestic, commercial, industrial, or agricultural products. Around the world, an enormous amount of agricultural residues is producing every year. Disposal of these agricultural residues have generated a secondary environmental pollution. This increases the researchers’ interest to produce porous adsorbent which can be derived from renewable, abundant, and low-cost substances generated from an agricultural origin [
Many agricultural wastes and natural adsorbents have been tested for the removal of the dyes from textile effluents [
Oladipo et al. [
Binary adsorption studies for the removal of reactive dyes from aqueous solution.
Binary dye system | Adsorbent | Adsorption capacity, |
Reference |
---|---|---|---|
Remazol Black B |
Wheat straw | 2.1 |
[ |
Reactive Remazol Red F-3B |
Coconut coir activated carbon | 2.01 |
[ |
Reactive Black-5, |
Palm kernel shell-activated carbon | — |
[ |
Reactive Orange 16, |
Sugar cane bagasse | 34.48 |
[ |
Reactive Orange 16, |
Modified rice husk | 1.829 |
[ |
Reactive Red, |
Activated carbon | 3.01 |
[ |
Reactive Blue 2, |
Chitosan-based hydrogel | 47.8 |
[ |
Reactive Orange 12 |
ZnS:Mn nanoparticles loaded on activated carbon | — |
[ |
Reactive Orange |
Modified rice hull | — |
[ |
However, limited studies have been reported to transform these agricultural residues to a suitable adsorbent for commercial application to remove dyes by using batch adsorption system [
In the present research, kenaf core fiber (KCF) residual was chemically modified with (3-chloro-2-hydroxypropyl)trimethylammonium chloride (CHPTAC) to alter the surface properties and increase surface area to develop more active sites to capture dyes from solution.
To date, the utilization of quaternized kenaf core fiber (QKCF) to adsorb binary reactive dyes has not been reported elsewhere. In the present work, the mechanism of dyes adsorption onto QKCF was studied to provide engineering information (e.g., uptake capacities and equilibrium time) to develop an adsorption design. The constants parameters that were obtained from equilibrium data of single dye were utilized to predict the binary adsorption behavior of dyes.
KCF was obtained from Institute of Tropical Forestry and Forest Product (INTROP) in Universiti Putra Malaysia. KCF coarse powder was sieved using 1 mm and 0.25 mm stainless steel sieves to get particles with size range from 0.25 mm to 1 mm. The sieved kenaf particles were washed a few times with tap water to get rid of dust and undesirable particles. The KCF powder was rinsed with distilled water and dried in an oven for 24 hours at 50°C.
The KCF was mercerized by soaking it in a solution of 6.25 mmol of NaOH for 24 hours. The basic medium swelled the fibers walls and opened the pores to improve KCF absorbency. Mercerized KCF (MKCF) was washed with distilled water and dried in an oven at 50°C for 24 hours.
The quaternization was accomplished by reacting each gram of dried MKCF with a solution consisting of 1.5 g of NaOH, 6.67 mL of (3-chloro-2-hydroxypropyl)trimethylammonium chloride (CHPTAC) solution (60 wt% in water), and 2.5 mL of water. The mixture was well-kept in a closed container at room temperature for 24 hours. Then, the quaternized kenaf core fiber (QKCF) was washed with 0.1% acetic acid solution to halt the reaction and rinsed with distilled water until neutral condition was achieved. Then, QKCF was dried at 50°C for 24 hours and kept in a closed container prior to use.
Fourier Transform-Infrared (FT-IR) Spectrometer 100 (PerkinElmer- precisely, United Kingdom) was used to record Infrared (IR) spectra. FT-IR spectrum was used in this study to identify the characteristic functional groups in QKCF.
Scanning Electron Microscope (SEM) (Hitachi Model S-3400N) was used to investigate the structure morphologies of QKCF. The SEM was registered at a magnification of 100
Reactive Red-RB (RR-RB) and Reactive Black-5 (RB-5) dyes were utilized as adsorbates in the present study. The structures of these two dyes and the general properties of selected reactive dyes are presented in Figure
General properties of reactive dyes.
Commercial name | Reactive Red-RB | Reactive Black-5 |
Chemical name | Reactive Red 198 | Remazol Black B |
|
288 | 599 |
Molecular weight (g/mol) | 967.5 | 991.82 |
Chemical formula | C27H18 |
C26H21N5Na4O19S6 |
Molecular structure of (a) Reactive Red-RB and (b) Reactive Black-5.
Adsorption isotherm for single-component solution was studied by using 250 mL Erlenmeyer flasks. The volume of dye was 100 mL in each flask, and the initial dyes concentrations for single-component solution were 100 mg/L. The dosage of QKCF was varying from 0.05 to 0.16 g/100 mL. All flasks were fully closed using aluminum foil to prevent evaporation and leakage. The incubator shaker was set at 200 rpm, 25°C, and 24 hours. The liquid and adsorbents were separated by using fast filter paper. The change in dye concentration in each solution was determined using a spectrophotometer UV-1800 (Shimadzu, Japan). The concentration of each dye was measured at maximum wavelength (
In binary systems, the ratio of mixing for each sample was 1 : 1, which mean that every 100 mL of dyes solution was prepared by mixed 50 mL of RR-RB dye with 50 mL of RB-5 dye. The concentration of each dye was changed depending on the experiments.
To investigate the influence of dye concentration on the removal efficiency of RR-RB in the presence of RB-5 dye, a varying concentration of RR-RB range from 25–100 mg/L was mixed with a fixed concentration of RB-5 (25 mg/L or 100 mg/L). In order to investigate the effects of dye concentration on the removal efficiency of RB-5 in the presence of RR-RB dye, a varying concentration of RB-5 range from 25–100 mg/L was mixed with a fixed concentration of RR-RB (25 mg/L or 100 mg/L). For all the experiments, three different pH (4, 6, and 8) were used and 0.1 g of QKCF dosage was added to each flask.
To investigation the effects of initial dye concentration, the two dyes were mixed with an equal concentration range from 20–200 mg/L. One g/L QKCF was added to each flask.
The study of the effect of adsorbent dosage was carried out at different weight of QKCF ranging from 0.05 to 0.25 g/100 mL while the concentrations of dyes in multicomponent are ranging from 25 to 100 mg/L.
Adsorption isotherm for a multicomponent solution was studied by using the same procedure flowed in single component and the dye concentration in multicomponent was kept constant at 100 mg/L.
The study of the effect of contact time was achieved by varying the dye concentrations in multicomponent from 20 to 100 mg/L. The samples were withdrawn at increasing contact time intervals ranging from 15 min to 180 min. From this study, the kinetics of adsorption was determined.
UV-spectrophotometer method is the common procedure for determination of the dye concentration in their mixture. To achieve that, linear relation between absorbance (
For binary system, the total absorbance
Therefore, to calculate the dye concentrations of each dye in binary solution, four calibration curves were built to determine four calibration coefficients using pure standards dyes of RR-RB and RB-5 of known concentration as illustrated in Figure
Calibration curves for RR-RB and RB-5 dyes at (a)
The FT-IR spectra of NKCF and QKCF are shown in Figure
FT-IR spectra for NKCF and QKCF.
SEM is a primary tool for characterizing the surface morphology and fundamental physical properties of the adsorbent surface. The textural structures of granular natural KCF (NKCF), mercerized KCF (MKCF), and quaternized KCF (QKCF) were observed by SEM images (Figure
SEM images: (a) natural KCF, (b) mercerization KCF, and (c) quaternization KCF.
BET analysis revealed that the surface area (SBET) increased from 2 m2/g for NKCF to 4 m2/g for QKCF. The average pore diameter of NKCF is 106 nm, and QKCF has an average pore diameter of 283 nm. Enlargement of the pore size is due to the dissolved lignin and hemicellulose in NaOH solution during the mercerization process. Furthermore, pore volume slightly decreased from 0.1699 cm3/g for NKCF to 0.1128 cm3/g for QKCF. It is attributed to the smoother texture of KCF surface after chemical quaternization.
Figures
Effect of initial RR-RB dye concentrations on the removal percentages of RR-RB dye by QKCF at different pH in the presence of (a) 25 mg/L of RB-5 dye and (b) 100 mg/L of RB-5 dye (QKCF dosage = 0.1 g/100 mL, agitation speed = 200 rpm, time = 4 hr., and temp. = 25°C).
RR-RB dye removals were increased from 93% of removal up to 98% of removal as the initial RR-RB dye concentrations were increased from 25 mg/L up to 100 mg/L (Figure
Figures
Effect of initial RB-5 dye concentrations on the removal percentages of RB-5 dye by QKCF at different pH in the presence of (a) 25 mg/L of RR-RB dye and (b) 100 mg/L of RR-RB dye (QKCF dosage = 0.1 g/100 mL, agitation speed = 200 rpm, time = 4 hr., and temp. = 25°C).
The variation of pH (pH 4, 6, and 8) in adsorption system for both cases (Figures
In RR-RB and RB-5 binary dye systems, RB-5 generally presented preferable adsorption on QKCF (Figure
Effect of equal initial RR-RB and RB-5 dyes concentration on the removal efficiency of both dyes in binary system (QKCF dosage = 0.1 g/100 mL, agitation speed = 200 rpm, time = 3 hr., and temp. = 25°C).
The percentage of removals of RR-RB and RB-5 in a binary system is shown in Figure
Effect of different adsorbent dosages in binary system with (a) 25 mg/L initial concentrations of RR-RB and RB-5, (b) 50 mg/L initial concentrations of RR-RB and RB-5, (c) 75 mg/L initial concentrations of RR-RB and RB-5, and (d) 100 mg/L initial concentrations of RR-RB and RB-5 (temperature = 25°C, agitation speed = 200 rpm, and adsorption time = 4 hr.).
Figure
Effect of contact time on the removal of RR-RB dye in the presence of RB-5 dye (binary system) (temp. = 25°C, speed = 200 rpm, dose = 0.1 g/100 mL, and con. of RR-RB = con. of RB-5).
Effect of contact time on the removal of RB-5 dye in the presence of RR-RB dye (binary system) (temp. = 25°C, speed = 200 rpm, dose = 0.1 g/100 mL, and con. of RR-RB = con. of RB-5).
Adsorption isotherms are basic requirements for any adsorption systems design. To quantify the adsorption capacity of adsorbents for the removal of adsorbate from aqueous solution, the equilibrium of a solute separated between liquid and solid phase is demonstrated by different models of adsorption isotherms. One of these adsorption isotherms is Langmuir isotherm model. The applicability of the isotherm equations was a comparison by referring to the correlation coefficient,
The equilibrium adsorption isotherms for RR-RB and RB-5 dyes adsorption onto QKCF are shown in Figures
Langmuir isotherm constants for RB-5 and RR-RB on QKCF in single system.
Dyes in single system | Langmuir constants | |||
---|---|---|---|---|
|
|
|
| |
RB-5 | 270.3 | 0.9024 | 243.9 | 0.95 |
RR-RB | 169.5 | 0.444 | 75.2 | 0.992 |
Langmuir adsorption isotherm of RR-RB onto QKCF (temp. = 25°C, agitation speed = 200 rpm, time = 24 hr., and initial dye concentration = 100 mg/L).
Langmuir adsorption isotherm of RB-5 onto QKCF (temp. = 25°C, agitation speed = 200 rpm, time = 24 hr., and initial dye concentration = 100 mg/L).
The equilibrium adsorption isotherms parameters for RR-RB and RB-5 dyes adsorption onto QKCF in binary experimental system are shown in Table
Langmuir isotherm constants for RB-5 and RR-RB in binary system.
Dye in binary system | Langmuir constants | |||
---|---|---|---|---|
|
|
|
| |
RB-5 | 142.86 | 2.414 | 344.83 | 0.9912 |
RR-RB | 116.3 | 0.18 | 20.8 | 0.9929 |
The Langmuir model can be extended for binary system dye to give (
Consequently, for the binary system of RR-RB and RB-5 dyes the extended Langmuir equation (after replacing the values of a parameter from Table
To evaluate the best fitted isotherm model, the sum of the squares of the errors (SSE), (
Figures
Extended Langmuir model for RB-5 in binary system with RR-RB (temp. = 25°C, speed = 200 rpm, time = 24 hr., and con. of RR-RB = con. of RB-5 = 100 mg/L).
Extended Langmuir model for RR-RB in binary system with RB-5 (temp. = 25°C, speed = 200 rpm, time = 24 hr., and con. of RR-RB = con. of RB-5 = 100 mg/L).
According to Jain and Snoeyink [
Figures
Jain and Snoeyink model for RB-5 in binary system with RR-RB (temp. = 25°C, speed = 200 rpm, time = 24 hr., and con. of RR-RB = con. of RB-5 = 100 mg/L).
Jain and Snoeyink model for RR-RB in binary system with RB-5 (temp. = 25°C, speed = 200 rpm, time = 24 hr., and con. of RR-RB = con. of RB-5 = 100 mg/L).
Overall, although the extended Langmuir model was failed to describe the data in the binary system, it is better to represent the binary system than the Jain and Snoeyink modified extended Langmuir model.
Kinetics adsorption study provides information about the mechanism of adsorption and also important for the qualification of the adsorption process [
In order to analysis the experimental data for adsorption kinetics of RB-5 and RR-RB onto QKCF, the pseudo-first-order and pseudo-second-order models were utilized. Equation (
The values of constant
Parameters and correlation coefficient (
Dye in binary system | Initial dye concentration (mg/L) |
|
Pseudo-first-order kinetic model | Pseudo-second-order kinetic model | ||||
---|---|---|---|---|---|---|---|---|
|
|
|
|
|
| |||
RB-5 | 20 | 19.5 | 1.83 | 0.01612 | 0.91 | 19.6 | 0.023 | 0.9999 |
40 | 39.3 | 3.57 | 0.028 | 0.9384 | 39.68 | 0.0157 | 1 | |
60 | 59.5 | 3.02 | 0.024 | 0.8213 | 59.88 | 0.0133 | 0.9999 | |
80 | 79.54 | 15.22 | 0.037 | 0.957 | 80.6 | 0.0055 | 1 | |
100 | 99.6 | 23.56 | 0.037 | 0.9812 | 101 | 0.0035 | 0.9999 | |
|
||||||||
RR-RB | 20 | 17.93 | 1.1 | 0.032 | 0.959 | 18.02 | 0.081 | 1 |
40 | 38.1 | 1.68 | 0.017 | 0.833 | 38.3 | 0.025 | 1 | |
60 | 57.88 | 1.71 | 0.0196 | 0.711 | 58.14 | 0.0189 | 1 | |
80 | 77.73 | 8.1 | 0.0341 | 0.928 | 78.7 | 0.0084 | 1 | |
100 | 97.5 | 9.22 | 0.0272 | 0.901 | 99 | 0.0055 | 1 |
Pseudo-first-order kinetic model for adsorption RB-5 in binary system with RR-RB (temp. = 25°C, speed = 200 rpm, dose = 0.1 g/100 mL, and con. of RR-RB = con. of RB-5).
Pseudo-first-order kinetic model for adsorption RR-RB in binary system with RB-5 (temp. = 25°C, speed = 200 rpm, dose = 0.1 g/100 mL, and con. of RR-RB = con. of RB-5).
The values of
Pseudo-second-order kinetic model for adsorption RB-5 in binary system with RR-RB (temp. = 25°C, speed = 200 rpm, dose = 0.1 g/100 mL, and con. of RR-RB = con. of RB-5).
Pseudo-second-order kinetic model for adsorption RR-RB in binary system with RB-5 (temp. = 25°C, speed = 200 rpm, dose = 0.1 g/100 mL, and con. of RR-RB = con. of RB-5).
The results of adsorption RR-RB and RB-5 dyes in binary system showed that QKCF can be effectively used as a bioadsorbent for the removal of anionic dyes. The QKCF bioadsorbent shows high sorption capacities toward RR-RB and RB-5. The kinetic studies stated that the adsorption kinetics of dyes on QKCF followed the pseudo-second-order model at different dye concentrations. According to the present study, one could conclude that the QKCF is an effective adsorbent for anionic dyes removal from coloured textile wastewater.
The authors declare that there is no conflict of interests regarding the publication of this paper.