Synthesis and characterization of carboxyl terminated poly(methacrylic acid) grafted chitosan/bentonite composite and its application for the recovery of uranium(VI) from aqueous media

Adsorption of uranium(VI) from aqueous solution using a novel magnetic hydrothermal cross-linking chitosan

“…Similar results had been reported for the uranium(VI) adsorption [17,24,25]. The positive value of DS indicated that randomness increase at the solid-solution interface in the adsorption reaction [26] and that the influence of entropy was more remarkable than enthalpy of activation [27].…”

A new extractant impregnated resin for separation of traces of uranium and thorium followed by their spectrophotometric determination in some geological samples

“…The band at 1022 cm −1 is assigned to the stretching vibration of S=O group. Moreover the bands were assigned to C-O at 1061 and 1105 cm −1 and the C=O band at 1635 cm −1 [46,48,49,[51][52][53]. The above mentioned bands indicate the modification of amberlite XAD 2010 with ARS.…”

“…The IR spectrum of amberlite XAD 2010 resin exhibited less intense band at 3436 cm −1 , which can be attributed to the stretching vibrations of adsorbed water [45]. The bands at 2924 and 1632 cm −1 are assigned to the aliphatic -CH 2 -CH 2 chains and the phenyl rings, respectively [46][47][48][49]. Upon modification with ARS, the phenolic-OH band appears at 3432 cm −1 [46,50].…”

Organic-Inorganic Hybrid Polymers as Adsorbents for Removal of Heavy Metal Ions from Solutions: A Review

“…Poly(methacrylic acid)-grafted chitosan/bentonite (CTS–g–PMAA/Bent) composite (Supporting information Figure S6) was synthesized for the adsorption of U(VI) [216]. They used N , N’ -methylenebisacrylamide as a crosslinking agent.…”

“…To study Sections 3.1–3.5, the characteristics of different kinds of organic-inorganic hybrid polymers were as follows: (1) Some functional groups of these adsorbents are –SH, –COOH, amines and –S–S–, –OH, –SO 3 − and ion exchange sites of hybrid polymer; (2) adsorption processes mostly obey the Langmuir isotherm that shows the adsorption is monolayer and there is a uniform distribution of sites on the surface of adsorbents; (3) the adsorption capacity of each certain organic functional group changes depending on its content [181,214], the used organic compound, inorganic support [166,195], crosslinking agent [212], aggregation of nanoparticles [253] and the used synthesis method [182,189]; (4) in some cases, organic compounds are used only for increasing thermal and mechanical stability of adsorbents and without adsorbing heavy metal ions [224]; (5) mesoprous compounds, due to their porous structures have a rather higher adsorption capacities compared to those of organically-functionalized layered, core-shell compounds and products of sol-gel method; (6) heavy metals as cations and oxyanions are adsorbed via electrostatic interactions and the increase in the hydrophobicity of functional groups of adsorbent (e.g., –N(C 2 H 5 ) 2 [156] or from –NH 2 to –NH(propyl) to –N(propyl) 2 [178]) decreases their adsorption capacity for metal cations and increases their q max values (e.g., from trimethylammonium to tri- n -butylammonium functional groups) for the adsorption of some hydrophobic oxyanions [183]; (7) In the most cases, for example [141–147,216,221,225,241,243,249,252], the used adsorbents are recovered by acid treatment and in the cases that acid dissolves the adsorbent [199], they have used another washing solutions; (8) some ions may react with metallic ions, e.g., Cl − with Hg 2+ [226], and inhibit their adsorption; (9) some ions, e.g., Cl − [183], SO 4 2− [196] or metallic cations [252], may react with functional groups of hybrid adsorbents and decrease their adsorption capacity for heavy metal ions; (10) steric hindrance on functional group decreases its adsorption capacity [151]; (11) in most cases, adsorption capacities of organic-inorganic hybrid polymers are bigger than those of their organic or inorganic constituents; (12) most of heavy metals were adsorbed in the pH range 4–7. With the increase in alkalinity of solution, heavy metal ions convert to metal hydroxides and this decreases their affinity for interaction with binding sites of adsorbents […”