Grafted Polyacrylamide Chains Research Articles

Enhanced separation of base metal sulfides in flotation systems using Chitosan-grafted-Polyacrylamides

• Chitosan-grafted-Polyacrylamide (Chi-g-PAM) was prepared and characterized. • Adsorption studies of Chi-g-PAM on metal sulfide surfaces were conducted. • Chi-g-PAM was tested as pyrite’s depressant in metal sulfide flotation. • Chi-g-PAM outperformed other depressants at producing less pyrite-diluted products. In this study, chitosan-grafted-polyacrylamide (Chi-g-PAM), a synthetic biocompatible polymer was investigated as a selective depressant of iron sulfide minerals [i.e., pyrite (FeS 2 )] in the flotation process of base metal sulfide minerals [i.e., galena (PbS), chalcopyrite (CuFeS 2 ), and sphalerite (ZnS)]. Chi-g-PAM was successfully synthesized by grafting polyacrylamide chains onto chitosan backbone. The synthesized polymer was characterized using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (SEM), and X-ray Powder Diffraction (XRD) analysis. Adsorption studies of Chi-g-PAM on mineral surfaces were conducted using zeta potential, contact angle, and total organic carbon (TOC) measurements in addition to X-ray Photoelectron Spectroscopy (XPS). Adsorption tests showed that Chi-g-PAM was most selective to pyrite as compared to the base metal sulfides indicating that this polymer may have the potential to be used as pyrite’s depressant in the flotation of base metal sulfides under specific conditions. XPS studies suggested that the depression of pyrite by Chi-g-PAM was due to chemisorption of the amine, amide, and hydroxyl groups of Chi-g-PAM at pyrite-water interface. The impact of Chi-g-PAM on the flotation response of sulfide minerals was investigated in both microflotation and batch flotation systems using model minerals and real sulfide ore, respectively. In microflotation tests of model minerals, the best separation efficiencies between valuable base metal sulfides and pyrite were achieved at pH 7. In batch flotation tests of complex sulfide ore of Mississippi Valley type (MVT) at natural pH (7.8), a separation efficiency of 61% was achieved between galena and pyrite when Chi-g-PAM was used compared to 35% with sodium cyanide (NaCN), the depressant that is commonly applied for this type of ore. However, the separation efficiency between chalcopyrite and pyrite was 15% and 21% with Chi-g-PAM and NaCN, respectively. Comparative studies indicated that Chi-g-PAM outperformed other depressants at producing less pyrite-diluted flotation concentrates.

Effect of gold nanocomposite treatment on male reproductive function

Recently, it has been proved that polymers with a dextran core and grafted polyacrylamide chains dextran–polyacrylamide are effective in photodynamic chemotherapy, which gives confidence in the prospect of drug nanosystem. However, further research is needed to determine the effect of the treatment on male reproductive function. Experiments have been conducted on 50 male and 50 females Albino white laboratory mice (25–30 g). Copolymer dextran-graft-polyacrylamide in nonionic (D-g-PAA) and anionic forms (D-g-PAA(PE) was used as a polymer matrix for in situ synthesis of gold nanoparticles (AuNPs). D-g-PAA consists of dextran core and five grafted PAA chains. The copolymer in anionic form was prepared by alkaline hydrolysis. Polymer/AuNP systems contain AuNPs of 2–11 nm in size and have spherical shape. The treatment of substances was carried out in the following way: D-g-PAA and D-g-PAA(PE) (10,00 mg/kg), D-g-PAA/AuNPs and D-g-PAA(PE)/AuNPs (9.78 mg/kg), saline solution was introduced intravenously (in the tail vein, in 0.3 mL) once a day, five times. For the first time, it has been shown that treatment with D-g-PAA, D-g-PAA(PE), and D-g-PAA/AuNPs did not affect reproductive function in male mice. Disorder of the male reproductive function occurs under conditions of treatment with D-g-PAA(PE)/AuNPs. Significant changes in the values of were established in: (1) pre- and post-implantation mortality of embryos; (2) the number of live newborns (pups); (3) sperm and abnormal sperm forms (%); (4) spermatocytes (primary) and spermatids (%); (5) living, apoptotic and necrotic cells in the testis (spermatocytes (primary)) and in the epididymis (spermatozoa).

The process of nickel nanoparticle formation in hydrophilic polymer/inorganic matrices

Polymer/inorganic hybrid based on silica sol and grafted polyacrylamide chains (SiO2/PAAm) was obtained by radical graft polymerization of acrylamide “from” unmodified silica surface. Its main parameters: RavSiO2, MvPAAm and N (the number of grafts per inorganic particle) were determined using static light scattering, elemental analysis, DTGA and viscometry. The hybrid was used as effective matrix in synthesis of NiNPs by borohydride reduction of Ni2+-ions in aqueous medium. A special approach to characterizing the kinetics and efficiency of NiNPs formation in pure water and hybrid solutions using UV-Vis spectroscopy was proposed and implemented. Due to this, an increase in the rate of accumulation and yield of NiNPs both in pure water and hybrid solutions with an increase in the Ni-salt concentration was established. In addition, a decrease in this rate with an increase in the concentration of hybrid matrices was found, as well as a slowdown in the reduction reaction in hybrid solutions compared to pure water. It was shown by TEM that the separate structural elements of the NiNPs/hybrid compositions are the swollen “hairy-type” hybrid structures with a size of ∼8.0–49.2 nm containing small (∼1.0–5.4 nm) NiNPs in PAAm “coronas.”

Experimental Approach to the Creation of Efficient Multicomponent Nanocomposites for Antitumor Therapy

Water-soluble polymers with special characteristics can be used as carriers in which the active ingredients are entrapped, encapsulated, adsorbed, or chemically attached. The understanding of the processes occurring during the formation of multicomponent nanosystems is the urgent task for the synthesis of antitumor nanocomposites. Gold nanoparticles (AuNPs), photosensitizer Chlorine e6 (Ce6), and Doxorubicin (Dox) are currently used for the photodynamic therapy and chemotherapy. We have been focused on the study of three-component nanosystems Polymer/AuNPs/Ce6, and four-component nanosystems Polymer/AuNPs/Ce6/Dox at physiological temperatures (37 ∘C). The star-like copolymer with Dextran core and grafted Polyacrylamide chains in nonionic and anionic forms are used as a matrix for the synthesis of nanocomposites. The nanosystems are characterized by the dynamic light scattering and transmission electron microscopy. The increasing of the aggregation processes for the four-component nanosystem Polymer/AuNPs/Ce6/Dox in comparison with the three-component one Polymer/AuNPs/Ce6 is registered. These nanosystems are tested in vitro against the subline of breast carcinoma MCF-7/S – sensitive to cytostatics. It is demonstrated that the increase of the aggregation process occurring in four-component systems leads to the loss of the antitumor activity of multicomponent drugs.

Tough, stretchable chemically cross-linked hydrogel using core–shell polymer microspheres as cross-linking junctions

A series of chemically cross-linked microgel composite hydrogels (MCH gels) with excellent toughness and stretchability were prepared using core–shell polymer microspheres as cross-linking junctions. In our strategy, MCH gels are obtained by connecting microspheres with polyacrylamide (PAAm) chains chemically grafted onto their surfaces, where an organic cross-linking agent is completely unnecessary. The mechanical behavior of the MCH gels was analyzed, and superresolution fluorescence microscopy and scanning electron microscopy were used to investigate their toughening mechanism. The results indicated that the homogeneous network structure resulting from the good compatibility between the core–shell microspheres and matrix was an important reason for the excellent toughness of the MCH gels. In addition to interactions among H bonds in the grafted PAAm chains, reversible deformation of the core–shell microspheres acting as cross-linking junctions, which arises from the flexibility of the microspheres, and the effect of cavitation between the microspheres and matrix could also effectively dissipate energy during deformation of the MCH gels.

Flocculation of both anionic and cationic dyes in aqueous solutions by the amphoteric grafting flocculant carboxymethyl chitosan-graft-polyacrylamide

In the current work, a series of amphoteric grafting chitosan-based flocculants (carboxymethyl chitosan-graft-polyacrylamide, denoted as CMC-g-PAM) was designed and prepared successfully. The flocculants were applied to eliminate various dyes from aqueous solutions. Among different graft copolymers, CMC-g-PAM11 with a PAM grafting ratio of 74% demonstrated the most efficient performance for removal of both the anionic dye (Methyl Orange, MO) and the cationic dye (Basic Bright Yellow, 7GL) under the corresponding favored conditions (80mg/L of the flocculant at pH 4.0, and 160mg/L at pH 11.0). In comparison with its precursors, chitosan and carboxymethyl chitosan, CMC-g-PAM11 showed higher removal efficiencies and wider flocculation windows. More importantly, the graft copolymer produced notably more compacted flocs based on image analysis in combination with fractal theory, which was of great significance in practical water treatment. Furthermore, the flocculation mechanism was discussed in detail. The grafted polyacrylamide chains were found to contribute much to the improved bridging and sweeping flocculation effects, but reduced charge neutralization flocculation for the effect of charge screening.

Microwave assisted polymer stabilized synthesis of silver nanoparticles and its application in the degradation of environmental pollutants

Abstract Graft copolymers of polyacrylamide (PAM) and dextran (Dx) are synthesized by grafting PAM chains onto a Dx backbone (Dx-g-PAM) with ceric ion induced solution polymerization technique. Partial hydrolysis of Dx-g-PAM is carried out with sodium hydroxide solution to obtain HDx-g-PAM. To synthesize silver nanoparticles dispersed copolymer nano-composite (Ag-HDx-g-PAM), reduction of silver ions with HDx-g-PAM is carried out using microwave heating. The environmentally benign and biodegradable copolymer, HDx-g-PAM acts as both stabilizer and reducing agent. The copolymer nano-composite, Ag-HDx-g-PAM is characterized by FT-IR, transmission electron microscopy, scanning electron microscopy and optical spectroscopy. Further, the catalytic activity of Ag-HDx-g-PAM nano-composite towards the reduction of environmental pollutants like phenosafranine dye and aromatic nitro compounds are studied.

Flocculation properties of polyacrylamide grafted carboxymethyl guar gum (CMG-g-PAM) synthesised by conventional and microwave assisted method

A novel polymeric flocculant based on polyacrylamide grafted carboxymethyl guar gum (CMG-g-PAM) has been synthesised by grafting polyacrylamide chains onto CMG backbone using conventional redox grafting and microwave assisted grafting methods. Under optimum grafting conditions, 82% and 96% grafting efficiencies have been observed in case of conventional and microwave assisted methods respectively. The optimum sample has been characterized using viscometry, spectroscopic analysis, elemental analysis, molecular weight and radius of gyration determination. The flocculation characteristics of grafted and ungrafted polysaccharides have been evaluated in kaolin suspension, municipal sewage wastewater and decolourization efficiency of a dye solution (methylene blue). It is evident from results that CMG-g-PAM synthesised by microwave assisted grafting method is showing best flocculation characteristics.

Synthesis and characterization of grafted carboxymethyl guar gum

AbstractGraft copolymers of carboxymethyl guar gum (CMGG) and polyacrylamide (PAM) have been synthesized by grafting polyacrylamide chains onto carboxymethyl guar gum backbone using a ceric‐ion‐induced solution polymerization technique. By varying the amount of initiator, three different grades of graft copolymers are synthesized. The characterization of graft copolymer is carried out by FTIR, NMR, intrinsic viscosity measurement, SEM, SLS, DTG, and rheology. A comparison of flocculation efficiency of CMGG and its graft copolymer shows that the graft copolymer exhibits better flocculation performance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

High performance polymeric flocculant based on hydrolyzed polyacrylamide grafted tamarind kernel polysaccharide (Hyd. TKP-g-PAM)

A high performance anionic flocculant was synthesized by partial alkaline hydrolysis of polyacrylamide grafted tamarind kernel polysaccharide. Various macromolecular characterizations were employed to confirm that partial alkaline hydrolysis of grafted polyacrylamide chains does take place. The flocculation characteristics of the hydrolyzed and unhydrolyzed grafted products were carried out in kaolin suspension and municipal sewage wastewater and it has been found that hydrolyzed product outperforms the unhydrolyzed grafted TKP.

Microwave assisted synthesis of polyacrylamide grafted dextrin (Dxt-g-PAM): Development and application of a novel polymeric flocculant

An efficient polymeric flocculant was synthesized by microwave assisted grafting of polyacrylamide to dextrin. By varying the reaction conditions, various grades of graft copolymers were synthesized to obtain the optimized one. Viscometry, elemental analysis, FTIR spectroscopy, 13C NMR spectroscopy, determination of molecular weight and radius of gyration using SLS analysis, thermal analysis and SEM analysis were employed to confirm that polyacrylamide has been grafted onto the dextrin backbone. The flocculation efficiency of the grafted products in kaolin suspension was dependent on the molecular weight, radius of gyration and length of the grafted polyacrylamide chains. The flocculant obtained by microwave assisted grafting method was superior to dextrin and polyacrylamide-based commercial flocculant (Rishfloc 226 LV) in flocculation tests.

Novel polymeric flocculants based on polyacrylamide grafted dextran in kaolin suspension

AbstractA study is done on ceric‐ammonium‐nitrate (CAN) initiated graft copolymerization of polyacrylamide (PAM) on to dextran (Dx) by solution polymerization technique. The average molecular weight of dextran is 7.0 × 10−6 g/mole. By changing the concentrations of the initiator in the reaction feed, a series of graft copolymer (Dx‐g‐PAM1 to Dx‐g‐PAM4) with variation in the number and length of the grafted PAM chains are obtained. The flocculation characteristics of various polymers are investigated by the use of settling tests in 2 wt % using kaolin suspensions. Among the series of graft copolymers, the one with highest molecular weight shows superior performance. The flocculation characteristics of the best‐performing graft copolymer (Dx‐g‐PAM3) are compared with those of various commercially available flocculants and PAM in the kaolin suspension. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Chelating resins for mercury extraction based on grafting of polyacrylamide chains onto styrene–divinylbenzene copolymers by gamma irradiation

Chelating resins for mercury adsorption were prepared by grafting polyacrylamide chains onto styrene–divinylbenzene (Sty–DVB) copolymers by applying gamma radiation. Sty–DVB copolymers were synthesized by aqueous suspension polymerization employing different synthesis conditions. The copolymers were characterized by apparent density, surface area, pore size distribution and swelling capacity. The copolymers were irradiated using a 60Co-γ source at room temperature in the presence of acrylamide solution in methanol. The grafting reaction was evaluated with the aid of elemental analysis, FTIR and thermogravimetric analysis (TGA). Hg(II) uptake measurements were carried out in batch experiments. The results showed that these resins can be successfully used for Hg(II) adsorption at ppm levels. The porosity degree of the copolymers influences the grafting yield as well as the Hg(II) complexation capacity of the chelating resins.

Studies on Mechanical and Antithrombogenic Behaviors of Polyvinyl Alcohol and Gelatin Based Novel Binary Polymer Blends with Grafted Polyacrylamide Chains

The aim of this study was to design a hydrophilic but mechanically strong macromolecular matrix to discover possible application as polymer scaffolds for tissue engineering and wound healing dressings. To achieve the objectives, acrylamide was polymerized by a redox couple in the immediate presence of polyvinyl alcohol, gelatin and a crosslinking agent (N, N′–methylene bis acrylamide). The structural and thermal characterization of the prepared hydrogels were carried out by Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC) which confirmed the formation of polyacrylamide grafted network and presented combined thermal features of the constituent polymers in their thermogram. The Environmental Scanning Electron Microscopy (ESEM) techniques were utilized for morphological characterization and the hydrogels were found to exhibit a highly porous structure. The hydrogels were also investigated for water sorption capacity and the extent of water intake was found to depend on the chemical composition of the gel. The blend hydrogels were also tested for their tensile strength and it was found that for a definite composition of the constituents of the gel the hydrogel offered optimum mechanical properties like tensile strength, percent elongation and Young's modulus. Thus, the intended objectives to design mechanically strong and blood compatible hydrogels were achieved.

Water‐Soluble Carbon Nanotubes by Redox Radical Polymerization

AbstractWater‐soluble single‐ and multi‐walled carbon nanotubes (CNTs) were prepared by grafting polyacrylamide chains from the graphitic surface via ceric ion‐induced redox radical polymerization. The reducing functionalities were covalently attached to the tubes by peroxide‐assisted radical reaction. The results showed that polymer chains were grafted onto CNTs by the redox process. The redox radical polymerization initiated by carbon nanotube‐bearing functionalities not only provides a powerful strategy for modifying the carbon nanostructures but also gives us the knowledge of their sidewall chemistry.magnified image

Modified Copolymers Dextran-graft-Polyacrylamide

The peculiarities of the alkaline hydrolysis of graft copolymers dextran-polyacrylamide with different molecular weights of the main polysaccharide and long grafted chains are studied by the potentiometric titration method. It is established that the degree of copolymers modification depends on the conformation of grafted polyacrylamide chains.

Characterization of graft copolymer based on polyacrylamide and dextran

Graft copolymers of dextran and polyacrylamide have been synthesized by grafting polyacrylamide chains onto dextran backbone using a ceric-ion-induced solution polymerization technique. By varying the amount of CAN (ceric ammonium nitrate) initiator, four different grades of graft copolymers (Dx-g-PAM) are synthesized. These graft copolymers are characterized by elemental analysis, infrared spectroscopy, intrinsic viscosity measurement, molecular weight determination, rheological technique, scanning electron microscopy, thermal analysis (DTG) and X-ray diffractometry. They exhibit efficient flocculation characteristics in various suspensions and viscosifying characteristics as well.

Development of graft copolymer flocculating agents based on hydroxypropyl guar gum and acrylamide

AbstractGraft copolymers of hydroxypropyl guar gum (HPG) with polyacrylamide (PAM) have been synthesized using a ceric ion‐induced solution polymerization technique at 28°C. Six graft copolymers have been synthesized with variation in the number and length of grafted PAM chains. The graft copolymers were characterized by viscometry, infrared (IR) spectroscopy, and thermal analysis studies. Flocculation jar tests were carried out in 0.25 wt % kaolin, iron ore, and silica suspensions. Among the series of graft copolymers, the one with fewest but longest PAM chains shows the better performance. The flocculation characteristics of this best performing graft copolymer are compared with various commercially available flocculants in the three suspensions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1776–1785, 2001

Shear and extensional investigations in solutions of grafted/ungrafted amylopectin and polyacrylamide

Various polysaccharides, such as starch and its constituent amylopectin, are used as flocculants in industrial effluent treatment. Grafting them with polyacrylamide branches enhances their flocculating and turbulent drag-reducing characteristics drastically. Aqueous solutions of the graft copolymer of amylopectin with polyacrylamide show a shear thinning non-Newtonian behavior. It is also expected that the solutions exhibit extensional effects. When the aqueous solution at 1000 ppm was subjected to a stretching device, the formation of a thread and reduction of the thread diameter with time were observed. The extensional relaxation time was thus estimated and compared with that of polyacrylamide. The measured relaxation time indicates that the performance of the rigid branched amylopectin, when grafted with fewer and longer polyacrylamide branches, is overwhelmed by the grafted polyacrylamide chains and the reduction of rigidity by the grafting process itself. This article reports the details of the investigations that led to these conclusions.

Novel flocculating agent based on sodium alginate and acrylamide

Graft copolymers of sodium alginate with polyacrylamide were synthesized using a ceric ion initiated solution polymerization technique at 27±1°C. Six graft copolymers have been synthesized with a variation in the number and length of grafted polyacrylamide chains. The graft copolymers have been characterized by viscometry, IR spectroscopy, SEM and XRD study. Their flocculation characteristics were evaluated in 0.25 wt% kaolin and 10 wt% iron ore suspensions. The flocculation behaviour of one of the above grades has been studied on a 1 wt% coal suspension. The flocculation characteristics of these grafted polymers were also compared with various commercially available polymeric flocculants. Among the grafted alginates, it was observed that, the graft copolymers containing longer polyacrylamide chains were the most efficient.