Suspension polymerization for synthesis of new hypercrosslinked polymers nanoparticles for removal of copper ions from aqueous solutions

Novel hypercrosslinked polymers nanoparticles (HCPNs) were designed by suspension polymerization technique with high surface area as well as HCPNs with functional groups have the affinity to removal of copper ions from aqueous solutions. Two HCPNs were synthesized through a two-step reaction, initially including the suspension polymerization of N-methacryloxytetrachlorophthalimide (NMTPA) with divinyl benzene (DVB) to give poly(NMTPA-co-DVB) and followed by the treatment of poly(NMTP-co-DVB) with triethylenetetramine (TETA) to give HCPNs (1) and with tetraethylenepentamine (TEPA) to give HCPNs (2). Using scanning electron microscopy and transmission electron microscopy, the surface morphology of the particles of the synthesized HCPNs was detected, and also, the particle size was measured. Also, the chemical structures of the synthesized compounds were illustrated by Fourier transform infrared spectroscopy and 1H-nuclear magnetic resonance (1H NMR). Thermal stability of the synthesized HCPNs was characterized by thermogravimetric analysis. The results illustrated that the particle size of the synthesized HCPNs is in range of 25–50 nm. The synthesized HCPNs compounds were reported for the separation of copper ions from wastewater, in which the results showed a very good affinity for these compounds for separation of copper ions from wastewater.


Introduction
The agglomeration of heavy metals produced from the industrial wastes in the water sources caused serious problems, in which these heavy metals are accumulated in the human body and become more harmful and very toxic for human health [1][2][3].
Some of pollutions occur in soil and water sources due to the presence of toxic heavy metals produced from industrial wastes.This caused bio-accumulation of these metals in human body, but is not degradable which stay in the body and need different ways for the separation.Electroplating, electronics and related devices are considered the reason for the presence of Cu 2+ in large scale found in wastewater which endangers human health.To avoid the serious problems caused due to the presence of toxic heavy metals in environment, it is necessary used ways to removal of these metals.The increase in concentration of heavy metals in living organisms and anthropogenic to serious levels can cause damage in human health [4,5].One of these metals is Cu 2+ ions which accumulate in kidneys, livers and with time damaged them.
Some of separations techniques are used for the removal of heavy metals from wastewater such ion exchange, precipitation, reverse osmosis, electrodialysis, adsorption, solvent extraction and separation by membranes technology [6,7].
The chelating sites that are found in resins can facilitate separation of Cu 2+ ions by the combination of the ionic and electrostatic interactions or through coordination with a high selectivity.A type of interactions is known as coordination which occurs due to the combination of chelating resins and Cu 2+ ions with a good selectivity.
Hypercrosslinked polymers (HCPs) are considered type of microporous organic materials.HCPs can be prepared by the crosslinking of linear polymer-precursors or through rarely crosslinked polymer.HCPs can be obtained by the two-or onestep methods.One of the methods is two steps for the synthesis where linear or low crosslinked polymer is first prepared and then hypercrosslinked obtained by free unreacted groups [8,9].The second method is characterized by one step for synthesis where the HCPs are directly formed through alkylation polymerization of monomers by Friedel-Crafts [10].
HCPs considered as new class of microporous organic materials [8,11].This is due to their chemical and thermal stability, the highly surface area and the simplicity with low cost in their preparation.HCPs showed a wide range in their applications, these applications in different fields as storage of the gas [12], carbon capture [13], catalysis applications [14], carriers for drug delivery system [15], sensing [16], and separation of heavy metals present in wastewater [17,18].Coulomb interactions in the material can be generated through the polymer containing ionic units, which can attract molecules or ions in the pores of material [19,20].So, the presence of ionic unit in HCP has great important.In 1970s, Davankov and Tsyurupa were the first which reported the HCPs [21,22].With high properties of HCPs for the catalysis, some of their limitations are shown like hydrophobicity and the absence of acid and base sites [23].

3
Resins with bis-picolylamine, iminodiacetate and sulfonic groups showed a high effectively for the separation of Cu 2+ ions.Through nitrogen and two oxygen atoms in iminodiacetate group which present three donated ligands that combined with Cu 2+ ions by cation exchange to form two types of bonds that represent in coordination and electrostatic bonds [24,25].
In this work, hypercrosslinked polymers nanoparticles (HCPNs) were synthesized by suspension polymerization technique with high surface area as well as HCPNs with functional groups which have the affinity to removal of copper ions from aqueous solutions.Two HCPNs were synthesized through two steps, the first step including the suspension polymerization of NMTPA with DVB to give poly(NMTPA-co-DVB) and the second step including the treated of poly(NMTPA-co-DVB) with TETA to give HCPNs (1) and with TEPA to give HCPNs (2).The chemical structure of the compounds was studied by different techniques.The sorption behavior of the HCPNs was studied for the separation of copper ions from wastewater.

Synthesis of N-Hydroxytetrachlorophthalimide (NHTPA)
N-Hydroxytetrachlorophthalimide is readily obtained in good yields by the treatment of tetrachlorophthalic anhydride with hydroxylamine hydrochloride in the presence of pyridine under reflux for 2 h.After 2 h, the solution was poured into crushed ice and neutralized with hydrochloric acid.Filtrate and wash the precipitate several times with water and leave it to dry at room temperature.

Synthesis of N-methacryloxytetrachlorophthalimide (NMTPA)
NMTPA was prepared by dissolving 0.01 mol of NHTPA and 0.01 mol of MAA in dry dichloromethane (DCM), and the reaction was kept under cooling.Drop by drop, the solution of DDC (0.01 mol of DDC dissolved in dry dichloromethane) was added to the above mixture.After completing the addition, the reaction was kept under stirring for 24 h.After completing the reaction, the precipitate (dicyclohexyl urea) was removed by filtration.The filtrate was evaporated using rotary evaporator to obtain product (NMTPA).The NMTPA monomer was recrystallized by mixture 1 3 of benzene and petroleum ether (40-60 °C) (20:80) (yield 93% and melting point 126-128 °C.

Synthesis of poly(NMTPA-co-DVB)
Polymerization through suspension method was used to synthesis of poly(NMTPAco-DVB).0.1 g of PVA dissolved in 100 mL distilled water and then added 10% aqueous NaCl solution.Dissolving 3.0 g of NMTPA and 2.0 g of DVB in 15 ml ethyl acetate (EA), then 0.05 g of the initiator (BP) was added.This solution was added to solution of PVA and heated at 90 °C under reflux, nitrogen and stirring for 24 h.After finishing copolymerization, centrifuge was used to obtain the fine precipitate.The removal of PVA, NaCl required washing the product with distilled H 2 O, and also, the removal of ethyl acetate and residue of unreacted NMTPA and DVB; the product washed with ethyl alcohol and acetone.The product was dried at room temperature.

Synthesis of hypercrosslinked polymers nanoparticles (HCPNs)
HCPNs were prepared by exchange reaction of poly(NMTPA-co-DVB) with different amines.In 10 ml toluene, add 0.5 g of poly (NMTPA-co-DVB) and 1 ml of TETA; then, the mixture was heated at 100 °C under reflux and stirring for 48 h.By using centrifuge, The HCPNs (1) was collected.The removal of NMTPA produced from exchange reaction and excess of TETA is necessary, so the product was washed several times with ethyl alcohol and acetone, respectively.The product was dried at room temperature to produce HCPNs (1).All steps were carried but with TEPA instead of TETA to give HCPNs (2).

Techniques and instrumentals for characterization
The spectra of Fourier transform infrared spectroscopy (FTIR) of the produced compounds were measured using FTIR-BRUKER, Vector 22 (Germany) Spectrophotometer in KBr phase in the region of 4000-400 cm −1 .The proton magnetic resonance spectrum (in dimethylsulfoxide (DMSO) as a solvent) for prepared monomer was recorded on Bruker 400 MHZ spectrophotometer.The chemical shift (Ϩ) is given downfield relative to tetramethyle silan (TMS) as internal standard.Morphology of the synthesized samples was reported using FE-SEM attached with EDX (ZEISS Sigma 300 VP, Germany) at an acceleration voltage of 10 kV.The transmission electron microscopy (TEM) images were obtained by using JEOL[JEM-2100 Electron Microscopy], which can also determine the particle size of HCPNs (1) and HCPNs (2).The samples of HCPNs (1) and HCPNs (2) were prepared as follows: the fine particles were dispersed in water by ultra-sonication.On a carbon coated copper grid, one drop of the dispersion was put and evaporated.The thermal behaviors of the prepared HCPNs were studied by lab Sys evo thermogravimetric analyzer under conditions of nitrogen as the atmosphere and temperature reach to 1000 °C at 10 °C/min represents the heating rate.To show the porous structure of the HCPNs, 1 3 surface area of the prepared HCPNs can be studied by Quantachrome TouchWin™ under nitrogen as adsorbent at 77.35 K.The concentration of copper ions was illustrated by using Hitachi atomic absorption Z-6100 polarized Zeeman spectrometer.

Experiments of the sorption process
All the following studies were reported by shaking 0.1 g of HCPNs in a solution of Cu 2+ ions (100 ml) at 300 rpm, 3 h and at 25 °C except the experiments for studying the influence of temperature.By using drops of solutions of hydrochloric acid and sodium hydroxide, the pH of the solution can be adjusted.After shaking the solution of Cu 2+ ions for 3 h, the HCPNs were separated from Cu 2+ ions solution using centrifuge and the remaining concentration of Cu 2+ ions in the filtrate was determined by atomic absorption.These studies were reported at different pH, initial concentration of Cu 2+ ions, shaking time and different temperatures to reach optimum conditions for adsorption process of Cu 2+ ions onto HCPNs.At the equilibrium, the capacity (q e ) (mmol/g) of sorption of Cu 2+ ions onto HCPNs can be given as following equation: where C o (mmol L −1 ) is the initial concentration of Cu 2+ ions and C e (mmol L −1 ) is the concentration of Cu 2+ ions remaining in the filtrate.V (L) and W (g) represent the taken volume of Cu 2+ solution and the weight (g) of HCPNs, respectively.

Synthesis
HCPNs (1,2) were synthesized by suspension polymerization of NMTPA monomer with DVB as crosslinking agent in the presence of PVA as stabilizer agent to control the average particle size to obtain poly(NMTPA-co-DVB), followed by exchange reaction with TETA and TEPA to obtain HCPNs (1,2) (Scheme 1).

FTIR spectra
Figure 1a, b shows spectra of FTIR and 1 HNMR for the prepared NMTPA.The bands obtained from spectra of FTIR for the prepared compounds showed the presence of functional groups in each compound to prove the occurring of the reaction by introducing a new group.The structure for NMTPA monomer was investigated through the spectrum of FTIR (Fig. 1a), which showed important bands at 2926 and 2854 cm −1 due to stretching vibration of C-H aliphatic and also at 1744 cm −1 related to stretching vibration of carbonyl group of phthalimide.The presence of C=CH 2 group was confirmed by the presence of band at 1628 cm −1 , which proved the reaction occurs between MAA and NHTPA to obtain NMTPA monomer.Also, Polymer Bulletin (2023) 80:12249-12270 1 3 a very characteristic band showed at 930 cm −1 for N-O. 1 H NMR was used to confirm the structure of NMTPA monomer (Fig. 1b), which showed Ϩ at 2.05 ppm (3H, CH 3 ) and Ϩ at 6.17-6.44 ppm (2H, CH 2 ).The spectra of poly(NMTPA-co-DVB), HCPNs (1) and HCPNs (2) are shown in Fig. 2a-c.The spectrum (Fig. 2a) showed also the presence of all bands in Fig. 1a.except band of C=CH 2 group which Scheme 1. Synthesis of HCPNs (1) and HCPNs (2) Polymer Bulletin (2023) 80:12249-12270 12254 disappeared due to the copolymerization process, but two new bands at 669 cm −1 and 3090 cm −1 were appeared attributed to four adjacent hydrogen atoms present in DVB and stretching vibration of C-H aromatic, respectively, which proved the introducing of DVB in copolymerization with NMTPA monomer to form the copolymer.The spectra of HCPNs (1) and HCPNs (2) (Fig. 2b, c) give two important bands at 3429 and 1631 cm −1 for N-H and carbonyl group of amide, respectively, in which the band of carbonyl group of phthalimide disappeared, and this proves the occurring of exchange reaction between different amine and copolymer to form HCPNs (1) and HCPNs (2).and HCPNs (2) can be determined by EDX analysis (Fig. 4), in which the percentage of exchange reaction with amine can be calculated.The results showed that the yield of the exchange reactions is 99.8% for HCPNs (1) and is 99.6% for HCPNs (2).

Surface area
The mesoporous structure of the prepared HCPNS (1) and HCPNs (2) was studied.The surface area, pore volume and average pore diameter for HCPNs (1) and HCPNs (2) were determined and are collected in Table 1.These data showed that the HCPNs (1) and HCPNs (2) have a high surface area.These data showed microporous structure for the prepared HCPNs (1) and HCPNs (2) [26] and also showed a good efficiency of these compounds toward adsorption and transfer of metals ions to internal sites due to the presence of pores in these compounds.

Thermal analysis
HCPNs are characterized by high thermal stability, so the thermal stability for HCPNs (1) and HCPNs (2) was examined by thermogravimetric analysis (TGA).
The TGA curves of HCPNs (1) and HCPNs (2) are shown in Fig. 5.In these curves, four decomposition stages were observed.The first stage from 25 to 94 °C and 27 to 122 °C for HCPNs (1) and HCPNs (2), respectively which this loss is due to evaporation of water and loss of volatile materials present out of the surface of HCPNs and also found into pores of the HCPNs.Due to high surface area of HCPNs (1) and HCPNs (2), these compounds can adsorb water vapor and some of volatile organic materials (VOCs) [27] and polar compounds found in samples of water [28].Second stage is starting from 94 to 242 °C and 122 to 262 °C for HCPNs (1) and HCPNs (2), respectively, which is due to the decomposition of grafted group in HCPNs (1) and HCPNs (2).From 242 to 584 °C and 262 to 830 °C for HCPNs (1) and HCPNs (2), respectively, the third stage begins.The fourth stage is from 584 to 928 °C and 830 to 984 °C for HCPNs (1) and HCPNs (2), respectively.Two latter stages can be due to decomposition of chain of polymer and crosslinking agents.

Studies for adsorption process
The effect of pH of solution One of important factors, that effect on the adsorption process through the coordination and electrostatic interaction of Cu 2+ ions and chelation sites is pH of solution.By using solutions of different pH, the sorption studies were investigated.The different pH of Cu 2+ solutions were prepared by using HCl and NaOH solutions.The pH ranging from 1.5 to 6 to obtain the optimum pH.The obtained results are shown in Fig. 6.We concluded that the capacity increased with increasing in pH of solution.Also, the data revealed that the sorption capacities of Cu 2+ ions are low at low pH values.The obtained results may be returned to competitive sorption of hydrogen ions against ions of Cu 2+ , which H + ions formed positive charge on chelating sites so the active adsorption sites are limited to Cu 2+ ions; for this reason, the adsorption capacities are low at low pH values.However, the increase in pH value showed decreasing in the concentration of H + , so this followed by increasing in sorption capacities.At pH equal to 6.0, the maximum adsorption capacities were obtained for both HCPNs (1) and HCPNs (2), in which this pH is the optimum pH.After pH 6.0, the precipitation of copper ions as metal(II) hydroxide was observed.

The sorption studies with change in initial Cu 2+ concentration
To study the role of initial copper concentration on the sorption process as well as the value of capacity, it is necessary to study the sorption process at different concentration of Cu 2+ ions at optimum pH.The initial Cu 2+ ion concentrations were 20, 40, 60, 80, 100 and 120 ppm.At these concentrations, the process was carried out with fixing all the factors as pH, mass of HCPNs and shaking time.In Fig. 7, the results illustrated that the sorption capacity increased with the concentration of Cu 2+ ions until all the chelating sites present in HCPNs become coordinated with the adsorbent, which this attend to equilibrium.At low concentrations, the sorption is very fast due to the availability of large number of chelating sites.Whereas, at the high concentrations the number of chelating sites decreased which attend to equilibrium.

Adsorption isotherm
The sorption isotherm can be expressed by studying the relation between the concentration of Cu 2+ ions in the interface and their concentration in bulk.Therefore, the sorption isotherms can explain the mechanism of sorption process.Langmuir, Freundlich and Temkin models are good tools used to explain this mechanism, and through the data obtained from these models, the explanation becomes more easily.The first model is known as Langmuir, in which, by this model, the relation between sorption capacity (q e ) with the concentration of Cu 2+ ions at equilibrium phase (C e ) can be explained.This model equation can be represented as follows [29]: where q e (mmol g −1 ) is the sorption capacity of Cu 2+ ions that adsorbed onto HCPNs, C e (mmol L −1 ) is the reaming concentration of Cu 2+ ions in the solution at the equilibrium, Q max is the theoretical maximum sorption capacity at monolayer and K presents constant (Lmmol −1 ) of Langmuir.By plotting the relation between 1/q e and 1/C e , a straight line is shown and Q max and K are calculated from the intercept and slope, respectively (Fig. 8).
R L is constant separation factor [30], which is dimensionless parameter and considered one of characteristic parameter for Langmuir model and by Eq. 3. R L can be obtained as follows: (2) where k is constant of Langmuir and C o (mmol/L) is the initial Cu 2+ ions concentration.The structure of the isotherm can be determined by the values of R L .If the value of R L is more than one, the shape of isotherm is unfavorable, and if R L is equal to one or zero, the shape of isotherm is linear or irreversible, respectively.But the shape of isotherm is favorable, when R L is less than one and more than zero [31].
According to the values of R L are given in Fig. 8, the isotherm is considered favorable due to values of R L lie between 0 and 1 for copper ions adsorbed through HCPNs (1) and HCPNs (2).
A second model described the heterogeneous of sorption process.This model is known as Freundlich.Equation 4 expressed on this model [32].
where q e (mmol/L) is the sorption capacity at equilibrium, C e (mmol/L) is the remaining concentration of Cu 2+ ions in solution at equilibrium, K F and N are constants of Freundlich.K F and N can be calculated from the slope and the intercept, respectively, from plotting log q e against log C e (Fig. 8).N is the most important parameter for Freundlich.This parameter can describe the nature of isotherm depending on it value.If the value of N is more than one, the isotherm is unfavorable, but if the value of N is equal to zero, the isotherm is irreversible.In the last case, when N is less than one and more than zero, the isotherm is favorable.In the results obtained from our work, the value of N is less than one and more than zero, and this indicated that the sorption of Cu 2+ ions through the HCPNs (1) and HCPNs (2) was favorable.
The following equation (Eq.5) is used to express on Temkin model [33] where B is known as constant of Temkin constant and K T is the constant of binding at equilibrium.All parameters from the three models are located in Table 2, in which results showed that Langmuir recorded a high value of correlation coefficient (R 2 ) for the Cu 2+ ions than Freundlich and Temkin.
In Table 3, the comparison of the present HCPNs (1) and HCPNs (2) with those of various types of adsorbents in other reported literatures is listed.

Sorption process with different contact time
The different shaking time between HCPNs (1) and HCPNs (2) and solution of Cu 2+ ions on the adsorption process was studied by change in adsorption capacity (q e ) values versus time (Fig. 9).In this figure, we observed that the sorption capacity of Cu 2+ ions is increased with increasing in contact time until the equilibrium is reached.This equilibrium is achieved after 3.5 hrs.Thus, the time, where the equilibrium occurred, was selected for the experiment of studding the effect of temperature.Fig. 9 The role of shaking time on the sorption process; 100 ml of Cu 2+ , 0.1 g HCPNs (1) and HCPNS (2), pH 6, 100 ppm, shaking rate 300 rpm and 25 °C 1 3

Kinetic studies
The mechanism of the sorption process can be explained by studying the kinetics of this process.From Lagergrens' pseudo-first-order, pseudo-second-order and intra-particle diffusion models, the kinetics of this process can be illustrated [40][41][42].
Lagergren and Svenska [40] illustrated the linear form of pseudo-first-order model in Eq. ( 6), while a pseudo-second-order model is expressed in Eq. 7.This model was fitted with the sorption of divalent heavy metals through adsorbent.At a short time, separation of Cu 2+ ions was achieved; this is due to the coordination and strong interaction between Cu 2+ ions and surface containing negative charges in chelating resin (active sites).The second-order equation is developed by Ho (Eq.( 7)) [41].
A diffusion mechanism cannot be explained through two above models; thus, Weber and Morris were applied equation for intra-particle diffusion model.Intra-particle diffusion model (Eq.8) [42].
The parameters from Eq. (6-8) can be defined as follows: q and q t represent the sorption capacity of Cu 2+ ions (mmol/g) at the equilibrium and at any time (t), respectively.K ads (min −1 ), K 2 and K id (mmolg −1 /min 0.5 ) are the rate constants for pseudo-first-order, pseudo-second-order and intra-particle diffusion, respectively.Intra-particle diffusion can be given some of explanation for sorption process according to the relation between q t and t 0.5 .If this relation gives straight line, this means that only rate limiting step was achieved for intra-particle diffusion.Whereas, two or more stages for the sorption of Cu 2+ ions were achieved in case of multilinearity [43].As shown in plotting present in Fig. 10, three steps were achieved for the sorption process: (a) First step involved the transfer or diffusion of Cu 2+ ions into the surface of HCPNs, (b) in second step (intra-particle diffusion), the Cu 2+ ions transfer from surface of HCPNs into the pores found inside the HCPNs and (c) the final step is achieved by the coordination of Cu 2+ ions with active sites, which in this step equilibrium is achieved.The parameters of three kinetic models and correlation factor (R 2 ) were estimated and are listed in Table 4.The data showed the fitting of pseudo-second-order model for the sorption of Cu 2+ ions into HCPNs (1) and HCPNS (2) than other models, in which the result gives an explanation for the sorption process that this process occurred through chemical reaction by complexation occurs between Cu 2+ ions and HCPNs (1) and HCPNS (2).
(6) log q − q t = log q − K ads 2.303 t

Influence of temperature and thermodynamics studies
One of the factors, which showed an influence on the sorption of Cu 2+ ions into the HCPNs (1) and HCPNs (2), is the temperature of solution.The experiments were applied at temperatures of 25, 40 and 60 °C, respectively, at optimum pH, concentration of Cu 2+ ions and contact time.
K d (ml g −1 ) is parameter known as distribution coefficient for the sorption process, which can be obtained by using the following equation: C o and C e (mmol L −1 ) are the initial and equilibrium Cu 2+ ions concentrations, respectively.V (L) is the volume taken from copper solution and W (g) is the weight taken from dry HCPNs to each experiment.
From Eq. 10, change in Free energy (ΔG o ads ) for the sorption study at different temperatures can be calculated.By using Eq.11, the relation between lnK d versus 1/T (Fig. 11) is plotted, in which the standard enthalpy change (ΔH o ads ) can be calculated from the slope and entropy change (ΔS o ads ) can be obtained from the intercept of this equation.
T (K) is the absolute temperature and R (8.314 Jmol −1 K −1 ) is the universal gas constant.
The parameters of ΔG o ads , ΔH o ads and ΔS o ads are collected in Table 5.The obtained results showed that the sorption process is endothermic process due to the positive values of ΔH o ads .Also, the positive values of ΔS o ads mean that the sorption process is random process.As results obtained in Table 5, the sorption process is spontaneous process due to ΔG o ads of the sorption process is negative value.Also, we observed that the sorption process is more effective at high temperature.This is due to the negative value of ΔG o ads increased with increasing in temperature.

Conclusion
Novel HCPNs were synthesized by suspension polymerization of the synthesized monomer (NMTPA) with DVB in the presence of PVA as stabilizer, followed by exchange reaction with TETA and TEPA to produce HCPNs (1) and HCPNs (2), respectively.The synthesized HCPNs can be applied in removal of copper ions from aqueous solutions due to high surface area.The nanoparticles structure and particle size were studied by SEM and TEM.The functional groups in the monomer, copolymer and HCPNs were investigated by FTIR.Also, the obtained data from TG analysis showed the thermal stability of the prepared HCPNs.The synthesized HCPNs showed a good affinity toward Cu 2+ ions.The adsorption process was studied in different conditions as pH of the prepared solution, initial Cu 2+ ions concentration, shaking time and temperature.The results showed that Langmuir model recorded the best results for the sorption process than Freundlich and Temkin models with the highest R 2 for the Cu 2+ ions, so the adsorption process fitted with Langmuir isotherm.The data obtained from kinetic studies showed the fitting of pseudo-secondorder model for the sorption of Cu 2+ ions into HCPNs (1) and HCPNS (2) than other models, in which the result gives an explanation for the sorption process that this process occurred through chemical reaction by complexation occurs between Cu 2+ ions and HCPNs (1) and HCPNS (2).The obtained results from thermodynamic studies showed that the sorption process is endothermic process due to the positive Table 4 The obtained results produced from Pseudo-first-order, Pseudo-second-order and Intra-particle diffusion model for sorption of Cu 2+ ions on the HCPNs (1) and HCPNS (2) Chelating resin Pseudo-first-order Pseudo-second-order Intra-particle diffusion HCPNs values of ΔH o ads .Also, the positive values of ΔS o ads mean that the sorption process is random process.The sorption process is spontaneous due to ΔG o ads of the sorption process is negative value.Also, we observed that the sorption process is more effective at high temperature.This is due to the negative value of ΔG o ads increased with increasing in temperature.
Funding Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB).
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Fig. 8 a
Fig. 8 a Langmuir isotherm, b Freundlich isotherm, c Temkin isothertm and d plotting R L with the initial Cu 2+ ions concentration (C o )

Fig. 10
Fig. 10 Intra-particle diffusion model for the sorption of Cu 2+ ions onto HCPNs

Table 1
The parameters obtained from BET surface area for HCPNs (1) and HCPNs (2)

Table 3
Comparison of maximum adsorption capacity of HCPNs (1) and HCPNs (2) with those of some other chelating resins reported in literature for the adsorption of Cu(II)

Table 5
The obtained parameters for thermodynamic studies of sorption Cu 2+ ions through the synthesized HCPNs (1) and HCPNs (2)