Poly(amidoxime) ligand derived from waste palm fiber for the removal of heavy metals from electroplating wastewater

Synthesis of amidoxime adsorbent prepared by radiation grafting on upcycled low-density polyethylene sheet for removal of heavy metals from wastewater

The issue of discharging waste, especially heavy metals from industrial activities into the environment, not only adversely impacts environmental quality but also has impacts on communities and human health. Removal and reduction of heavy metal contamination in rivers and wastewater are, therefore, critical initiatives that require significant attention. This work studied the removal of heavy metals, including Zn(II), Cu(II), As(III), and Pb(II) by utilizing an upcycled amidoxime low-density polyethylene sheet (AO-sheet). The synthesized AO-sheet was analyzed for various physical properties, including scanning electron microscope, energy-dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. For the batch adsorption experiment, parameters affecting adsorption capacity were studied: initial concentration, submerging time, and pH. Adsorption isotherms were also studied. The results of the heavy metal adsorption study showed that the initial concentration was the most significant parameter; the higher the initial concentration, the greater the adsorption capacity. The adsorption capacity of Zn(II) and Pb(II) increased with submersion time, which achieved 21.07 and 0.855 mg/g-adsorbent, respectively, after four weeks of submersion under the highest initial concentration studied. The adsorption capacity of Cu(II) was 7.98 mg/g-adsorbent after two weeks of optimal adsorption duration under the highest initial concentration studied. The adsorption capacity of As(II) was 1.07 mg/g-adsorbent after one week of optimal submersion time under the highest initial concentration studied. Moreover, the appropriate pH range for effective adsorption of Zn(II), Cu(II), and Pb(II) was identified as 8-9, while for As(III), it was 6-8, with an adsorption duration of 0.43 weeks (3 days). From the Langmuir isotherm, it was found that the adsorption of this work was characterized by monolayer adsorption. The results demonstrate that the AO-sheet can be effectively used to remove heavy metals from wastewater. Its potential for reusability was up to 8 cycles, with the Zn(II) adsorption capacity being reduced to about 20.37%.

Sustainable grafted chitosan-dialdehyde cellulose with high adsorption capacity of heavy metal

A novel adsorbent was prepared using a backbone comprising chemically hybridized dialdehyde cellulose (DAC) with chitosan via Schiff base reaction, followed by graft copolymerization of acrylic acid. Fourier transform infrared spectroscopy (FTIR) confirmed the hybridization while scanning electron microscopy (SEM) revealed intensive covering of chitosan onto the surface of DAC. At the same time, energy dispersive X-ray (EDX) proved the emergence of nitrogen derived from chitosan. The X-ray diffraction (XRD) indicated that the crystallinity of the backbone and graft copolymer structures was neither affected post the hybridization nor the grafting polymerization. The adsorbent showed high swelling capacity (872%) and highly efficient removal and selectivity of Ni2+ in the presence of other disturbing ions such as Pb2+ or Cu2+. The kinetic study found that the second-order kinetic model could better describe the adsorption process of (Cu2+, Ni2+) on the graft copolymer. In contrast, the first-order kinetic model prevails for the binary mixture (Pb2+, Ni2+). Moreover, the correlation coefficient values for the adsorption process of these binary elements using Langmuir and Freundlich isotherms confirmed that the developed grafted DAC/chitosan exhibits a good fit with both isotherm models, which indicates its broadened and complicated structure. Furthermore, the grafted DAC/chitosan exhibited high efficient regeneration and high adsorption capacity for Pb2+, Cu2+ and Ni2+.

Perspectives and prospects of chelation extraction of heavy metals from wastewater: A review

Heavy metals' contamination of water resources is a global environmental issue due to their detrimental effects on human health. To safeguard humans and the environment, toxic heavy metals must be removed from contaminated water because they cannot be broken down. Diverse technologies are employed to reduce the levels of heavy metals in wastewater. However, these technologies suffer from being either costly or ineffective, particularly when the effluent has extremely low residual amounts. This review outlines the main accomplishments and promising future directions for solvent extraction as one of the potential methods of extracting heavy metals from water, utilizing literature reports. In addition to reviewing some of the commercial chelating reagents now in use, this article also discusses some of the obnoxious effects on human health that are associated with exposure to heavy metals.

Removal of Cu (II) Ions from Aqueous Solution Using Poly-Amidoxime Resin from Grafted Millet Husk Cellulose

Poly-amidoxime ligand was synthesized on the cellulose isolated from millet husk through a graft copolymerization process for adsorption of Cu (II) ion from aqueous solution. The functional group, thermal degradation and morphology of the adsorbent were investigated by Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA) and scanning electron microscope (SEM), respectively. The FTIR results showed that grafting was successful due to the presences of 2244 cm-1 for cyano group (CN) and also band at 1640 cm-1 and 1380 cm-1 that replaced 2244 cm-1 which successfully confirmed the synthesis of poly(amidoxime) functional group. The TGA showed two stages of thermal degradation 12 % weight loss observed in amidoxime at 240 0C which is due degradation of amidoxime functional group then it reduces to 2% in second stage at 530 0C which revealed the improved thermal stability of the material. The SEM image showed a clear morphology of the absorbent before adsorption and after adsorption. The Initial concentration, adsorbent dosage and contact time were taken as independent variables. The adsorption process was optimized by central composite design (CCD) in Response surface methodology (RSM). The predicted value is in good agreement with experimental value and also the ANOVA result showed that all the independent variables have significant impact with the adsorbent. The optimum condition achieved in the experiment was at initial concentration of 150 mg/L, adsorbent dosage of 0.3 g and contact time of 90 min for Cu2+ with percentage removal of 55.41 % predictably and 54.92 % experimentally.

Efficient remediation of chlorpyrifos pesticide from contaminated water by superparamagnetic adsorbent based on Arabic gum-grafted-polyamidoxime

A novel organic/inorganic biosorbent hydrogel nanocomposite based on Arabic Gum-grafted-polyamidoxime and CuFe₂O₄ magnetic nanoparticles (AG-g-PAO/CuFe₂O₄) was prepared in three steps. The prepared hydrogel nanocomposite was well characterized using Fourier transform infrared (FT-IR), energy-dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), CHN, zeta potential, and Brunauer-Emmett-Teller (BET) analyses. The adsorption efficiency of the AG-g-PAO/CuFe₂O₄ for removing an organophosphorus pesticide (OPP) (chlorpyrifos) from aqueous solutions was studied. Effect of different experimental conditions such as the pH of the solution, adsorbent dosage, contact time, initial concentration on adsorption efficiency was evaluated. The experimental adsorption data described well by the Langmuir isotherm model and the maximum adsorption capacity (Q_max) of the prepared biosorbent for chlorpyrifos was found 769.23 mg/g. The adsorption kinetic data were well fitted by the pseudo-second-order model. It was suggested that the chlorpyrifos was adsorbed onto AG-g-PAO/CuFe₂O₄ hydrogel biosorbent mainly through electrostatic interaction and hydrogen bonding. The result of adsorption-desorption experiments revealed that the AG-g-PAO/CuFe₂O₄ can be excellently regenerated and reused after three sequential runs without a considerable decline in its adsorption performance.

Nitrile-Functionalized Poly(2-oxazoline)s as a Versatile Platform for the Development of Polymer Therapeutics

In recent years, polymers bearing reactive groups have received significant interest for biomedical applications. Numerous functional polymer platforms have been introduced, which allow for the preparation of materials with tailored properties via post-polymerization modifications. However, because of their reactivity, many functional groups are not compatible with the initial polymerization. The nitrile group is a highly interesting and relatively inert functionality that has mainly received attention in radical polymerizations. In this Article, a nitrile-functionalized 2-oxazoline monomer (2-(4-nitrile-butyl)-2-oxazoline, BuNiOx) is introduced, and its compatibility with the cationic ring-opening polymerization is demonstrated. Subsequently, the versatility of nitrile-functionalized poly(2-oxazoline)s (POx) is presented. To this end, diverse (co)polymers are synthesized and characterized by nuclear resonance spectroscopy, size-exclusion chromatography, and mass spectrometry. Amphiphilic block copolymers are shown to efficiently encapsulate the hydrophobic drug curcumin (CUR) in aqueous solution, and the anti-inflammatory effect of the CUR-containing nanostructures is presented in BV-2 microglia. Furthermore, the availability of the BuNiOx repeating units for post-polymerization modifications with hydroxylamine to yield amidoxime (AO)-functionalized POx is demonstrated. These AO-containing POx were successfully applied for the complexation of Fe(III) in a quantitative manner. In addition, AO-functionalized POx were shown to release nitric oxide intracellularly in BV-2 microglia. Thus nitrile-functionalized POx represent a promising and robust platform for the design of polymer therapeutics for a wide range of applications.

Adsorption of Metallic Ions on Amidoxime-Chitosan/Cellulose Hydrogels

Adsorption using natural compounds is an attractive separation technique for recovering heavy metals from aqueous media. Although chitosan, which is a natural polysaccharide, is an environmentally benign adsorbent, it dissolves in an acidic aqueous medium. In this study, we prepared adsorbents consisting of chitosan modified with amidoxime groups for improving metal adsorptivity, and cellulose for improving gel stability using an ionic liquid, and examined their adsorption characteristics for metal ions. The prepared amidoxime-chitosan/cellulose hydrogels had a mechanical strength without cross-linking. All the investigated metals were adsorbed on the amidoxime-chitosan/cellulose hydrogels in the following adsorptivity order: Cu ≈ Ag > Ni > Zn. The adsorptivity of the metal ions increased with pH due to a proton exchange reaction. From the Langmuir adsorption isotherm, the Langmuir constant for Cu exceeded those of other metals because amidoxime has higher Cu affinity. The pseudo-second-order reaction model best described the adsorption kinetics with metal chelate formation being the rate-determining step. Because amidoxime-chitosan/cellulose hydrogels had higher physical stability and higher Cu selectivity, they were found to be a promising, environmentally benign adsorbent.

Heavy Metals Removal from Water by Efficient Adsorbents

Natural occurrence and anthropogenic practices contribute to the release of pollutants, specifically heavy metals, in water over the years. Therefore, this leads to a demand of proper water treatment to minimize the harmful effects of the toxic heavy metals in water, so that a supply of clean water can be distributed into the environment or household. This review highlights several water treatment methods that can be used in removing heavy metal from water. Among various treatment methods, the adsorption process is considered as one of the highly effective treatments of heavy metals and the functionalization of adsorbents can fully enhance the adsorption process. Therefore, four classes of adsorbent sources are highlighted: polymeric, natural mineral, industrial by-product, and carbon nanomaterial adsorbent. The major purpose of this review is to gather up-to-date information on research and development on various adsorbents in the treatment of heavy metal from water by emphasizing the adsorption capability, effect of pH, isotherm and kinetic model, removal efficiency and the contact of time of every adsorbent.

Waste Fiber-Based Poly(hydroxamic acid) Ligand for Toxic Metals Removal from Industrial Wastewater

Toxic metals in the industrial wastewaters have been liable for drastic pollution hence a powerful and economical treatment technology is needed for water purification. For this reason, some pure cellulosic materials were derived from waste fiber to obtain an economical adsorbent for wastewater treatment. Conversion of cellulose into grafting materials such as poly(methyl acrylate)-grafted cellulose was performed by free radical grafting process. Consequently, poly(hydroxamic acid) ligand was produced from the grafted cellulose. The intermediate products and poly(hydroxamic acid) ligand were analyzed by FT-IR, FE-SEM, TEM, EDX, and XPS spectroscopy. The adsorption capacity (q_e) of some toxic metals ions by the polymer ligand was found to be excellent, e.g., copper capacity (q_e) was 346.7 mg·g⁻¹ at pH 6. On the other hand, several metal ions such as cobalt chromium and nickel also demonstrated noteworthy sorption capacity at pH 6. The adsorption mechanism obeyed the pseudo second-order rate kinetic model due to the satisfactory correlated experimental sorption values (q_e). Langmuir model isotherm study showed the significant correlation coefficient with all metal ions (R² > 0.99), indicating that the single or monolayer adsorption was the dominant mode on the surface of the adsorbent. This polymer ligand showed good properties on reusability. The result shows that the adsorbent may be recycled for 6 cycles without any dropping of starting sorption capabilities. This polymeric ligand showed outstanding toxic metals removal magnitude, up to 90–99% of toxic metal ions can be removed from industrial wastewater.

Heavy Metals Removal from Electroplating Wastewater by Waste Fiber-Based Poly(amidoxime) Ligand

An efficient and economical treatment technology for heavy metal removal from the electroplating wastewaters is needed for the water purification. Therefore, pure cellulosic materials were derived from two waste fiber (pandanus fruit and durian rind) and conversion of the cellulose into the poly(acrylonitrile)-grafted material was accomplished by free radical grafting system. Thereafter, poly(amidoxime) ligand was produced from the grafted materials. Sorption capacity (qe) of several toxic metals ions was found to be high, e.g., copper capacity (qe) was 298.4 mg g−1 at pH 6. In fact, other metal ions, such as cobalt chromium and nickel also demonstrated significant sorption capacity at pH 6. Sorption mechanism played acceptable meet with pseudo second-order rate of kinetic pattern due to the satisfactory correlation with the experimental sorption values. A significant correlation coefficient (R2 > 0.99) with Langmuir model isotherm showed the single or monolayer sorption occurred on the surfaces. The reusability study showed that the polymer ligand can be useful up to six cycles with minimum loss (7%) of efficiency and can be used in the extraction of toxic metal ions present in the wastewaters. Therefore, two types of electroplating wastewater were used in this study, one containing high concentration of copper (23 ppm) and iron (32 ppm) with trace level of others heavy metals (IWS 1) and another containing high concentration of copper (85.7 ppm) only with trace level of others heavy metals (IWS 2). This polymeric ligand showed acceptable removal magnitude, up to 98% of toxic metal ions can be removed from electroplating wastewater.

Highly Active Cellulose-Supported Poly(hydroxamic acid)-Cu(II) Complex for Ullmann Etherification

Highly active natural pandanus-extracted cellulose-supported poly(hydroxamic acid)-Cu(II) complex 4 was synthesized. The surface of pandanus cellulose was modified through graft copolymerization using purified methyl acrylate as a monomer. Then, copolymer methyl acrylate was converted into a bidentate chelating ligand poly(hydroxamic acid) via a Loosen rearrangement in the presence of an aqueous solution of hydroxylamine. Finally, copper species were incorporated into poly(hydroxamic acid) via the adsorption process. Cu(II) complex 4 was fully characterized by Fourier transform infrared (FTIR), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectrometry (ICP-OES), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses. The cellulose-supported Cu(II) complex 4 was successfully applied (0.005 mol %) to the Ullmann etherification of aryl, benzyl halides, and phenacyl bromide with a number of aromatic phenols to provide the corresponding ethers with excellent yield [benzyl halide (70-99%); aryl halide (20-90%)]. Cu(II) complex 4 showed high stability and was easily recovered from the reaction mixture. It could be reused up to seven times without loss of its original catalytic activity. Therefore, Cu(II) complex 4 can be commercially utilized for the preparation of various ethers, and this synthetic technique could be a part in the synthesis of natural products and medicinal compounds.

Amidoxime-functionalized bead cellulose for the decomposition of highly toxic organophosphates

Regenerated bead cellulose is a promising material with excellent mechanical and rheological properties, ideally suited for advanced environmental applications. By introducing the amidoxime functional group into the glucose unit at the C-6 position, highly effective reactive sorbent was prepared and used to destroy priority hazardous substances such as organophosphate pesticides or nerve-paralytic chemical warfare agents (CWAs). Quantum mechanical (QM) calculations were performed to study the interactions of organophosphates with amidoxime functional groups at the molecular level. It was found that the energetic reaction barrier of the rate-limiting step is markedly reduced (from 31.40 to 11.37 kcal mol⁻¹) in the case of the amidoxime-catalysed degradation of parathion methyl, which resulted in a dramatic increase in the degradation rate; this was fully confirmed by experiments, in which the pesticide degradation proceeded at the time scale of several hours (t_1/2 = 20–30 hours at pH 7.22).

Amidoxime-functionalized bead cellulose accelerates the cleavage of phosphoester bonds in toxic organophosphates.

Polymer Ligands Derived from Jute Fiber for Heavy Metal Removal from Electroplating Wastewater

Industrial operations, domestic and agricultural activities worldwide have had major problems with various contaminants caused by environmental pollution. Heavy metal pollution in wastewater also a prominent issue; therefore, a well built and economical treatment technology is demanded for pollution-free wastewater. The present work emphasized pure cellulose extracted from jute fiber and further modification was performed by a free radical grafting reaction, which resulted in poly(methyl acrylate) (PMA)-grafted cellulose and poly(acrylonitrile)-grafted cellulose. Subsequently, poly(hydroxamic acid) and poly(amidoxime) ligands were prepared from the PMA-grafted cellulose and PAN-grafted cellulose, respectively. An adsorption study was performed using the desired ligands with heavy metals such as copper, cobalt, chromium and nickel ions. The binding capacity (qe) with copper ions for poly(hydroxamic acid) is 352 mg g-1 whereas qe for poly(amidoxime) ligand it was exhibited as 310 mg g-1. Other metal ions (chromium, cobalt and nickel) show significance binding properties at pH 6. The Langmuir and Freundlich isotherm study was also performed. The Freundlich isotherm model showed good correlation coefficients for all metal ions, indicating that multiple-layers adsorption was occurred by the polymer ligands. The reusability was evaluated and the adsorbents can be reused for 7 cycles without significant loss of removal performance. Both ligands showed outstanding metals removal capacity from the industrial wastewater as such 98% of copper can be removed from electroplating wastewater and other metals (cobalt, chromium, nickel and lead) can also be removed up to 90%.