Sorption Equilibrium Behaviour of Post-Characterized Bio-Filled Waste PET (RIC-1) Bottles Composites

Sorption Equilibrium Behaviour of Post-Characterized Bio-Filled Waste PET (RIC-1) Bottles Composites

Cyprian Yameso Abasi*, Onyinyechi Gift Aliene, Sheila Yabiteighha

Department of Chemical Sciences, Niger Delta University Wilberforce Island Bayelsa State, Nigeria

*Corresponding Author

DOI: https://doi.org/10.51244/IJRSI.2025.12010030

Received: 24 December 2024; Accepted: 03 January 2025; Published: 05 February 2025

ABSTRACT

The sorption equilibrium of characterized bio-filled waste PET(RIC-1) bottle composites was investigated. Composites were made by melt-mixing of PET(RIC-1) matrix and bio-fillers as crab shell, clay, and chitin. The adsorption capacities of the binary and ternary composites for Fe (III) ions were determined through equilibrium methods from adsorption isotherm models. In terms of equilibrium isotherm application, the ternary composites PET/CHITIN/CLAY and PET/CBS/CLAY fitted best with the Langmuir isotherm (R² = 0.9861) than the Freundlich isotherm (R² = 0.9411). The Freundlich isotherm was better suited to the binary composites PET/CBS and PET/CLAY; the physisorption conformity suggested from the Freundlich isotherm was confirmed by the high Polanyi potential (Ɛ²) values greater than 40 kJ/mol in the Dubinin-Radushkevich isotherm. Overall, the findings demonstrate the potential of these composites for adsorption applications and thus open a route of use of PET waste that has become an environmental pollution threat.

INTRODUCTION

Plastics make up part of solid waste whose management is captured in the eleventh and twelfth goals of the United Nations Sustainable Development Goals (SDGs).

Plastic pollution is one of the most pressing environmental challenges of our time. A previous study by Jambeck et al., (2015) estimated that about 8 million tonnes of plastic end up in the oceans every year, which is a huge problem for marine life, fisheries, tourism, and the marine environment as a whole. The problem has become much more pressing due to the doubling of plastic manufacturing worldwide in the last 40 years. According to the study by Jambeck et al., (2015), Nigeria was listed as the ninth largest contributor to marine plastic pollution. Other nations that contribute significantly to plastic trash include China, Indonesia, the Philippines, Vietnam, Sri Lanka, Thailand, Egypt, and Malaysia. A later study on the models of global riverine plastic emissions into the oceans by Meijers et al., (2021) put Nigeria on the eleventh  position.  A most recent study on local-to-global emission of macroplastics by Cottom et al., (2024) ranked Nigeria as the third highest emitter, ahead of China that was the previous highest. The non-biodegradable nature of plastics has presented significant environmental challenges informing the choice of the theme ‘’BEAT PLASTIC POLLUTION’’ for the world environmental day in 2018 (Oladele, 2018) and 2023. Despite various programmes and interventions aimed at addressing the plastic waste problem, such as public awareness campaigns (Alhassan et al., 2010), the progress has been limited. PET waste composites are now being used for treatment of industrial wastewater (Bhuyan et al.,2023).

Another environmental problem and resource loss are caused by the millions of metric tonnes of bio-waste that is generated each year by the worldwide shell-fishery business. A large amount of this garbage consists of crustacean shells (Yan and Chen, 2015). However, according to Su et al., (2019), there is a lot of promise in using crab shells as fillers in polymer composites. Similarly, clay a plentiful and affordable raw material has been recognized as  good for adsorption or combined pollutant removal, because of their surface-bound exchangeable cations and anions (Kim et al., 2004).

In addition to plastic pollution, water contamination by heavy metals is a growing concern, a heavy metal like iron is naturally occurring in ground water formation and can be introduced into water supplies by human activities connected to iron’s industrial uses. Even though it is important for metabolism, it can be harmful in large doses. In water, it is a major cause for worry due to the metallic taste it imparts, which is detectable even at low quantities of 1.8 mg/L (Ujiele and Joel, 2013).

By analyzing the sorption equilibrium behaviour of post-characterized bio-filled waste PET(RIC-1) bottle composites, insights can be gained into their effectiveness in equilibrium adsorption applications, particularly in the removal of contaminants from water such as iron. The kinetic and diffusion behaviour was earlier considered in our article, Aliene and Abasi (2025); herein we present the equilibrium sorption behaviour of bio-filled waste PET(RIC-1) bottle composites.

MATERIALS AND METHODS

Reagents and chemicals

The analytical purity of all the substances utilized was guaranteed. Iron (III) nitrate, nonahydrate, Fe (NO₃)₃·9H₂O was obtained from Sigma-Aldrich, U.S.A. Molychem of India supplied the sodium hydroxide (NaOH) pellets, which were 97% pure. Hydrochloric acid (HCl) 35-38% (1.18 gcm^-3) was obtained from Qualikems Laboratory Reagents, India. Sodium Chloride (NaCl) 99.5% AR/ACS grade was obtained from Loba Chemie PVT. LTD, India.

Preparation of Matrix for Composite Samples

Waste PET(RIC-1) water bottles were collected from drainages, streets, dumpsites and eateries around a University community in Bayelsa state, Nigeria. To get rid of any surface contaminants or commercial labels, the PET bottles were cleaned using a combination of detergent and tap water. The bottles were allowed to air-dry after being rinsed with distilled water. After the bottles were dried and cleaned, they were ground into powder using a stainless-steel grater and then another part was chopped into little pieces using a pair of scissors. The PET powder was then sieved into a fine size by passing it through a 1.0 mm standard sieve.

Preparation of Composite Bio-fillers

Crab shells:  The live crabs were gotten from Abalama in Rivers State, Nigeria. The flesh and tissues of the crab were removed from the shell leaving the crab shell clean.  The empty shells were washed and sun-dried till there was no more water in it for four days. The sun-dried shells were broken into smaller pieces and taken for grinding and thereafter sieved in a 1.0 mm standard sieve.

Clay: The clay was collected from a depth of 10 – 30 cm with a hand tool from the Abana-enem lake fringe subsurface at Ogu-Atissa, Bayelsa State. It was then oven- dried for two days and sieved in a 1.0 mm standard sieve.

Chitin: Chitin was extracted from crab shells through demineralization and deproteinization. 20 g of the ground and sieved crab shells, hydrochloric acid (HCl) and sodium hydroxide (NaOH) were used in the chitin preparation process. Distilled water was also used to prepare desired concentration of the chemical solutions and to wash the sample.
Demineralization experiment: Crab shells contain minerals like calcium carbonate, which needed to be removed to obtain pure chitin. Demineralization was achieved as reported by Aung et al., (2018).This is by treating the ground shells with an acid, such as hydrochloric acid (HCl). The acid dissolves the minerals while leaving the chitin intact. 1M of dilute HCl was prepared and 20 g of the 1.0 mm sieved crab shell was weighed into two separate beakers. The crab shell was soaked in 100 mL of the dilute HCl, stirred continually till frothing subsided. The mixture was allowed to soak for 6 hours. After the 6 hours, the demineralized crab shell was filtered and washed continually till the water ran clean, and then it was oven-dried at a temperature of 105 °C.

Deproteinization: After the demineralization, chitin and protein residues remained. To remove the proteins, an alkaline treatment was used. 1M of sodium hydroxide (NaOH) solution was prepared and used to break down and solubilize the proteins, leaving chitin behind. The dried demineralized shell weighing 16.9 g was soaked in 100 mL of the dilute NaOH for 3 hours and heated to a temperature of 105.0(±1) °C. They were washed and filtered till clean. The wet chitin was weighed at a mass of 26.9 g before drying at a temperature of 105.0(±1) and after every 15 minutes the chitin was weighed until a constant weight of 12.1 g was obtained.

Preparation of Composites

A stainless pan was placed on an electric hot plate for 1 minute and 120 g of the shredded PET was weighed and put inside the pot to melt. When the PET was melted at 80 ºC, 30 g of 150 µm of crab shell was weighed and added to the molten PET. The mixture was whisked together to allow uniformity of the blended mixture. This was then poured unto a flat board for curing for about 15 minutes in air. This whole process was repeated for all different composite: PET/Chitin, PET/Clay, PET/Clay/Chitin and PET/Chitin/Crab shells composites in the ratio 4:1 for the binary composites and 4:1:1 for the ternary composites.

Characterization of Composites

Fourier Transform Infrared Spectrometer (FTIR) Analysis

In order to identify the functional groups that would be employed as adsorption sites for the adsorption of Fe (III)ions, Fourier Transform Spectrometer (FTIR) spectrometer was utilized for all composite analyses.

Physicochemical characterization: Determination of True Density, Bulk Density and Porosity 

An empty density bottle was weighed with stopper as W1. The density bottle was filled with solvent (distilled water) and weighed as W2. The density bottle was emptied, and then 2 g  of the  composite was weighed and transferred into the empty density bottle as W3. Distilled water was added to fill the density bottle containing the 2 g composite and weighed as W4. These measurements were then used to calculate the true density, bulk density and porosity. 

Determination of pH point at zero charge (pHpzc)

20 mL of 0.01M NaCl solution was placed in various sample vials and adjusted with 0.1M HCl and 0.1M NaOH solutions, to pHs of 2, 4, 6, 8, 10 and 12 consecutively. 0.2 g of binary and ternary composites were weighed and added to each sample vials and shaken for an hour with a shaker. After 48 hours, the final pH of the solutions was measured. The final pH was subtracted from the initial pH to obtain the change in pH (ΔpH). A plot of ΔpH versus initial pH was drawn to determine the composites. Determination of surface area

The surface area of the composites was determined using Sear’s method (Ebelegi et al., 2023). 0.2 g of each composite sample was weighed into a beaker containing 25 mL of 0.1M HCl. 1 g of NaCl was added and mixed thoroughly. The mixture was titrated with a standard solution of 0.1M NaOH till a pH of about 9 was achieved.

Effect of Concentration on Adsorption

0.1g was weighed respectively for the different adsorbent (PET, Chitin, Clay, Crabshell, PET/Chitin, PET/Clay, PET/Crabshell, PET/Chitin/Clay and PET/Crabshell/Clay) into various test tubes. 10 mL of serial dilutions 10, 20, 40, 60, 80, 100 and 120 ppm of iron (III) nitrate stock solution was prepared and added to the various test tubes. Each composite and single materials were shaken for 100 minutes and supernatants were taken for UV-Visible analysis.

RESULTS AND DISCUSSION

The results of the equilibrium sorption behaviour of iron(III) ions on bio-filled composites are presented and discussed herewith.

Figure 1:  Effect of concentration on adsorption of iron (III) ions using single materials, binary and ternary composites

Effect of Concentration

Figure 1 shows the adsorption of Fe (III) ions on the single materials, binary composites, and ternary composites at 25°C, with concentrations ranging from 10-120 ppm. With the exception of PET, which showed a continuous decline in adsorption, the data shows that adsorption increases steadily with increasing initial metal ion concentration. The most linear increase of adsorption with concentration was seen in PET/Crabshell/Clay, a ternary composite. The binary composites also had good linear increase but at a lower concentration than  PET/Crabshell/Clay. This trend is  also reflected in the percentage adsorption  values of the composites.

Figure 2: Percentage adsorption of iron (III) ions using single materials, binary and ternary composites

Percentage Adsorption

Among all the composites PET/CBS/CLAY had the best adsorption, supporting the porosity test where PET/CBS/CLAY had the highest porosity of 88.68%, Aliene and Abasi,(2025). The highest adsorption percentage of the composite PET/CBS/CLAY was 90.10% noted at 120 ppm while the lowest was at 28.125% at 10 ppm. PET/CHITIN /CLAY also had a steady rise in its adsorption from 10-80 ppm but began to drop at 100 ppm. Its highest percentage adsorption of 75.39% was observed at 80 ppm while its lowest percentage adsorption was 43.75% at 10 ppm. For the binary composites, PET/CHITIN showed a steady rise from 10-120 ppm and dropped at 100 ppm, its highest adsorption was 83.203% noted at 80 ppm and lowest percentage adsorption was at 21.875%. Similarly, PET/CBS showed a steady rise in its percentage adsorption from 10-80 ppm but dropped at 100 ppm, its highest percentage adsorption 75.39% was noted at 80 ppm while the lowest percentage adsorption was 40.625% at 10 ppm. PET/CLAY had its highest percentage adsorption at 75.39% when the concentration was 80 ppm and its lowest at 37.5% when the concentration was at 20 ppm. The trend of the result can be attributed to the relative availability of vacant sites on the composites for the uptake of ferric ions in the solution. The decline in percent adsorption  in some of the composites apart from  PET/CBS/CLAY towards the equilibrium time may be due to desorption or saturation of available sites.

Equilibrium Behaviour of Composites 

The adsorption data was applied to some adsorption isotherm models in order to know the predominant equilibrium adsorption behaviour of the composites. Figures 3 – 18 show the plots of the isotherm models of the adsorbents (composites) used in the adsorption study.

Figure 3: Langmuir isotherm for the adsorption of Fe (III) ions by PET/CHITIN/CLAY composite

Figure 4: Langmuir isotherm for the adsorption of Fe (III) ions by PET/CBS/CLAY composite

Figure 5: Langmuir isotherm for the adsorption of Fe (III) ions by PET/CBS composite

Figure 6: Langmuir isotherm for the adsorption of Fe (III) ions by PET/CLAY composite

Figure 7: Freundlich isotherm for the adsorption of Fe(III) ions by PET/CBS/CLAY

Figure 8: Freundlich isotherm for the adsorption of Fe(III) ions by PET/CHITIN/CLAY composite

Figure 9: Freundlich isotherm for the adsorption of Fe(III) ions by PET/CLAY composite

Figure 10: Freundlich isotherm for the adsorption of Fe(III) ions by PET/CBS composite

Figure 11: Temkin isotherm for the adsorption of Fe (III) ions by PET/CBS/CLAY composite

Figure 12: Temkin isotherm for the adsorption of Fe (III) ions by PET/CHITIN/CLAY composite

Figure 13: Temkin isotherm for the adsorption of Fe (III) ions by PET/CLAY composite

Figure 14: Temkin isotherm for the adsorption of Fe (III) ions by PET/CBS composite

Figure 15: Dubinin- Radushkevich isotherm for the adsorption of Fe (III) ions by PET/CLAY

Figure 16: Dubinin- Radushkevich isotherm for the adsorption of Fe(III) ions by PET/CBS

Figure 17: Dubinin- Radushkevich isotherm for the adsorption of Fe(III) ions by PET/CLAY

Figure 18: Dubinin-Radushkevich isotherm for the adsorption of Fe(III) ions by PET/CHITIN/CBS

A substance concentration in a solution is related to the amount adsorbed per unit mass of adsorbent, as shown by the adsorption isotherm. To better plan adsorption systems in the future, it is essential to have a firm grasp of the equilibrium parameters (Witek-Krowiak et al., 2011). As stated by Bulgariu and Bulgariu, (2012), these isotherms may be utilized to assess the adsorptive capabilities of different adsorbents for different contaminants. The parameters of these isotherms represent the surface properties and variable affinities of the adsorbent. This work makes use of the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms, among others.

According to the Langmuir isotherm, a monolayer of adsorbed material forms at predetermined, homogeneous locations on the adsorbent. In equation (1), we find the equation that represents this isotherm.

—————————– Equation (1)

In this context, (C_e) refers to the equilibrium concentration in mg/L; (q_e) measures the quantity of adsorbate at equilibrium in mg/g; (q_m) denotes the amount of iron (III) ions adsorbed to create a full monolayer in mg/g, and (K_L) denotes the adsorption equilibrium constant (dm³/mg). From the expression in (1)  the Langmuir isotherm equation can be linearised as in equation (2).

——————– Equation (2)

The values of (q_m) and (K_L) are obtained by analyzing the linear plot of (C_e/q_e) against (C_e) and finding the slope (1/q_m) and intercept (1/K_Lq_m), or a plot of 1/q_e vs.1/C_e.

Thirdly, here we see the Freundlich isotherm, an empirical equation for describing systems with heterogeneity:

The value of q_e is equal to the product of K_F and C_e raised to the power of (1/n), with the formula seen in (3).

q_e = K_F C_e ^1/n ——————————————– Equation (3)

The Freundlich isotherm constants are denoted by (K_F) and (1/n). The linearisation of this equation can be seen in (4):

Log q_{e =} Log K_F +   Log C_e —————————————————- Equation (4)

The uniform distribution of binding energies over several surface exchange sites is proposed using the Temkin isotherm model (Kauser et al., 2013). Equation (5) represents the Temkin isotherm in its linear version:

q_{e =} B In A + B In C_e   —————————————————-Equation (5)

In this case, (B = RT/b_T) where R corresponds to the universal gas constant (8.314 J mol^-1 K^-1) and the absolute temperature in Kelvin is denoted by T. The equilibrium binding constant is denoted by A measured in dm³g^-1, whereas the heat of sorption is represented by B. The adsorption potential of the adsorbent,  b_T, is measured in (Jmol^-1) and C_e equals the equilibrium residual concentration of metal ion (mg/L). Assuming a pore-filling process for adsorption, the Dubinin-Radushkevich (D-R) isotherm model provides a semi-empirical equation for this type of adsorption. It applies to physical adsorption processes, postulating that van der Waals forces are involved, and implying that adsorption is multilayer in nature (Bopari et al., 2011). Equation (6) represents the D-R isotherm model in its linear form:

ln q_e  = ln q_D – 2B_DƐ²   —————————————–Equation (6)

The variables in the equation include q_D, the D-R constant in milligrammes per gramme (mg/g),  Ɛ is the Polanyi potential  given by the equation 7:

Ɛ= RT ln(1+1/C_e) ———————————————Equation (7)

Where R is the universal gas constant 8.314 Jmol^-1K^-1, and T is the absolute temperature in Kelvin.

The type of adsorption can be estimated using the sorption mean free energy, which is represented by E, which can be expressed as in equation 8:

E = (2B_D) ^-1/2———————————————- Equation (8)

Where, B_D is  a constant related to the sorption mean free energy,E. When,

sorption mean free energy (E) is less than 40kJ/mol, physisorption occurs,

sorption mean free energy (E) is greater than 40 kJ/mol, chemisorption occurs,

sorption mean free energy (E) within (8-16) kJ/mol,  it is ion exchange and

sorption mean free energy (E) < 8 kJ/mol, the adsorption is physical  in nature.

The results of the isotherms parameters are given in Table 1.

Table 1: Adsorption isotherms parameters for binary and ternary composites

ISOTHERM	PARAMETERS	PET/CBS	PET/CLAY	PET/CBS/CLAY	PET/CTN/CLAY
Langmuir	qm (mg/g) KL (L/g) R2 r	0.0647 -0.1884 0.8638 0.9294	0.0642 -0.1940 0.7025 0.8315	-0.1741 -0.4079 0.8446 0.919	0.0503 24.15 0.9861 0.9930
Freundlich	kF (mg/g) n R2 r	0.1510 0.5656 0.8874 0.9420	0.5704 1.2742 0.9294 0.9641	0.0000027 0.1550 0.8245 0.9080	0.0176 0.5529 0.9411 0.9701
Temkin	kT (dm3/g) bT (J/mol) R2 r	4.0629 x 107 19,040.15 0.9348 0.9669	3.2766 x 109 23,116.40 0.793 0.8905	2.6092 x 10 15 53,524.89 0.9851 0.9925	3.1641 x 105 15,007.58 0.7907 0.8892
Dubinin Radushkevivh	Qd  (mg/g) BD E (kJ/mol) R2 r	3.0485 x 104 0.0004 35.36 0.9401 0.9696	2.2784 x 106 0.0005 31.62 0.9386 0.9688	3.2801 x 107 0.0001 70.72 0.8611 0.9279	7.3209 x 109 0.00015 58.82 0.7081 0.8415

Table 1 displays the results of equilibrium modelling for Fe (III) ions using various composites to assess adsorption capacity and heat of sorption. A strong correlation coefficient (r) in the PET/CTN/CLAY composite indicated the presence of both chemisorption and physisorption, as it matched both the Freundlich and Langmuir isotherm models. Nonetheless, the Langmuir model was better fitted with high value of r = 0.9930 compared to the Freundlich isotherm model where r = 0.9701, indicating that the adsorption sites were suitable for monolayer  adsorption of Fe (III) ions. This conclusion is in line with what Asuquo and Martin, (2016) found when they investigated the adsorption of cadmium ions from water using sweet potato peel. The high correlation coefficient of 0.9701 in the Freundlich isotherm is also indicative that multilayer adsorption also occurs on the composite. PET/CBS/CLAY ternary composite sample had low coefficient of determination (R²) values of 0.8446 for Langmuir and 0.8245 for Freundlich isotherm model. Despite the poor fitting to the adsorption model it was observed from the result that Langmuir R² value was higher compared to Freundlich indicating the prevalence of chemisorption among the ternary composites. However, the correlation coefficient (r) values were all greater 0.9 which indicates that the strength of the relationship between the variables is high.

The binary composites, PET/CBS and PET/CLAY had a poor fit for the Langmuir and Freundlich adsorption models, with the exception of PET/CLAY that had a nearly perfect fit of R² value of 0.9294 as against Langmuir R² value of 0.7025. Despite, the low fitting of adsorption data to fit the isotherm models, R² value of 0.8874 for the Freundlich isotherm model was higher than R² values of 0.8638 for the Langmuir isotherm model. The correlation coefficient (r) values for the binary composites for the Freundlich model are also greater than 0.94 and so the data were strongly and positively correlated. The adsorption intensity parameter for the Freundlich adsorption isotherm model (n) from the table for the binary composites were seen to be 0.5656 and 1.2742 for PET/CBS and PET/CLAY respectively: this is an indication of a good adsorption, because the range of n values considered to be favourable for adsorption is 0 to 1. The resultant values of the Langmuir and Freundlich  isotherms  of the binary composites indicate that, although there is a simultaneous occurrence of physisorption and chemisorption, adsorption of Fe (III) ions on the binary composites is non-homogeneous.

A robust interaction between the metal and the reactive groups of the sorbent was shown by the composite PET/CBS/Clay’s alignment with the Temkin isotherm, which displayed a R² value of 0.9851 and PET/CBS with a R² value of 0.9348.The adsorption potential parameter b_T for both binary and ternary composites are greater than 1 kJmol^-1;  this is an indication that the composites have very significant adsorption potential for the sorbate.With the exception of PET/CLAY and PET/CTN/CLAY with r values of 0.8905 and 0.8892 respectively,  all other composites had r values greater than  0.96 for the Temkin  model, which implies that the adsorption data of the composites were strongly and positively correlated.

The Dubinin-Radushkevich(D-R) isotherm was appropriately fitted by the PET/CBS and PET/CLAY binary composites, with R² values of 0.9401 and 0.9386, respectively. Except for PET/CTN/CLAY with r value of 0.8415, all the other composites had  r values greater 0.92, and so the data were strongly and positively correlated by this model.The predominance of physisorption among the binary composites PET/CBS and PET/CLAY earlier observed in the Freundlich isotherm parameters was confirmed by D-R  sorption mean free energy (E) values of 35.36 and 31.62 kJ/mol respectively. All the E values for the binary composites were less than 40 kJ/mol. Although, the R² values of the ternary composites, 0.8611 for PET/CBS/CLAY and 0.7081 for PET/CTN/CLAY did not properly fit the adsorption data there mean free energy, were higher than 40 kJ/mol corroborating the chemisorption prevalence indicated by the Langmuir isotherm.

Earlier, in a similar work, Abasi, Ebiyegbagha and Godwin(2023), reported the use of the plastic-derived composites to adsorb samples of iron-contaminated water in real time. These composites in the present study with plastic matrix, can as well be applied  to remediate metal contaminants of water samples in real time. The PET bottle materials used for this study were sourced easily because they are readily available as  environmental waste. The use of Crab shells, though a  covering to natural nutrition  resource from the environment, may not spell a threat to the ecosystem, because they are mostly discarded after extraction of edible parts and the  fractional ratio of use as a filler is very low compared to PET waste bottle matrix.

Suggestions for future work

Poor fitting of some of the isotherms were observed and this  may be due to surface complexities arising from the surface area of contact and desorption  after site saturation. The study needs be extended to the use of surface morphology to determine surface characteristics  and  thermodynamics to determine  sticking probability and other thermodynamic properties of adsorption on these composites.

CONCLUSION

The study on the sorption equilibrium behaviour of post-characterized bio-filled waste PET(RIC-1) bottles composites highlights the potential of these materials as sustainable alternatives for the adsorption of heavy metals like Fe (III). Analyses of the equilibrium data using isotherm models revealed that the sorption process aligns with Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm. Also, it was determined that chemisorption was the main mechanism driving the adsorption process for the ternary composites. E values higher than 40 kJ/mol for Dubinin-Radushkevich isotherm as well as high R² values from Langmuir corroborated the indication of a chemisorption process for the ternary composites; while the binary composites were controlled by physisorption which is supported by E values less than 40 kJ/mol in the Dubinin-Radushkevich isotherm and high R² value in the Freundlich model. Both composites and single materials showed steady increase with rise in initial metal ion concentration. Overall, the sorption equilibrium behaviour of the composites show that they are eco-friendly and  have very significant potential for removal or remediation of aqueous pollutants exemplified by iron (III) ions; their present use in this work presents a low cost material and application  route  for reducing and recycling of waste plastics from the environment.

Conflict Of Interest

There is no conflict of interest among the authors of this work.

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