Environmentally friendly Pd(II) recovery from spent automotive catalysts using resins impregnated with a pincer-type extractant.

Extractant-impregnated resins have potential for recovering platinum group metals selectively and efficiently. Herein, 1,3-bis(2-(octylthio)propan-2-yl)benzene (1), a pincer-type extractant, was impregnated in Amberlite XAD-7 resin (1-EIR), and the batch Pd(II) sorption conditions, including impregnated amount, shaking time, Pd(II) concentration, HCl concentration, and Pd(II) desorption reagents, were optimized. The maximum Pd(II) sorption capacity of 1-EIR was 49 mg g after 24 h in a 700 ppm Pd(II) solution.

Rapid and selective recovery of palladium from platinum group metals and base metals using a thioamide-modified calix[4]arene extractant in environmentally friendly hydrocarbon fluids.

A novel macrocyclic calix[4]arene extractant having a long alkyl chain thioamide, 25,26,27,28-tetrakis(N-n-octylthiocarbamoyl)methoxy-5,11,17,23-tetra-tert-butylcalix[4]arene (1), was synthesized from 25,26,27,28-tetrakis(N-n-octylcarbamoyl)methoxy-5,11,17,23-tetra-tert-butylcalix[4]arene (2) using Lawesson's reagent. Extractant 1 was characterized using H NMR, C NMR, FT-IR spectroscopy, and elemental analysis. The Pd(II) extraction abilities of 1 and 2 were studied in high-boiling-point and environmentally friendly hydrocarbon diluents.

Crystal structure of a supra-molecular lithium complex of --butyl-calix[4]arene.

Crystals of a supra-molecular lithium complex with a calix[4]arene derivative, namely tetra-methano-llithium 5,11,17,23-tetra--butyl-25,26,27-trihy-droxy-28-oxidocalix[4]arene methanol monosolvate, [Li(CHOH)](CHO)·CHOH or [Li(CHOH)]·(calix[4]arene)]·CHOH (where calix[4]arene represents a mono-anion species because of deprotonation of one H atom of the calixarene hy-droxy groups), were obtained from --butyl-calix[4]arene reacted with LiH in tetra-hydro-furan, followed by recrystallization from methanol. The asymmetric unit comprises one mono-anionic calixarene mol-ecule, one Li cation coordinated to four methanol mol-ecules, and one methanol mol-ecule included in the calixarene cavity. The calixarene mol-ecule maintains a cone conformation by intra-molecular hydrogen bonding between one phenoxide (-O) and three pendent calixarene hy-droxy groups (-OH).

Synthesis of pincer-type extractants for selective extraction of palladium from PGMs: An improved liquid-liquid extraction approach to current refining processes.

SCS pincer ligands 1-4 were synthesised, and their ability to extract Pd(II) from HCl and HNO media was studied. The Pd(II) extraction properties of 1-4 were compared with those of commercial extractants (DOS and LIX84-I) in kerosene. 1 and 2 showed superior Pd(II) extractability (E% = 99.

Preparation of amino terminated polyamidoamine functionalized chitosan beads and its Cr(VI) uptake studies.

Chitosan beads, functionalized by amino terminated hyperbranched dendritic polyamidoamine (up to 3rd generation) were prepared by Michael addition of methyl acrylate to amino groups on the chitosan surface and amidation of terminal ester groups by ethylene diamine. All the three generation chitosan beads were used for chromium removal along with raw chitosan beads. However, the 3rd generation polyamidoamine chitosan beads (3ACB) have been protonated using HCl (3ACBP)/loaded with zirconium using ZrOCl(2)·8H(2)O (3ACBZr) to enhance the sorption capacity towards Cr(VI).

Preparation and characterization of silica gel/chitosan composite for the removal of Cu(II) and Pb(II).

Silica gel/chitosan composite (SiCS) was prepared via., sol-gel method by mixing silica gel and chitosan and cross-linked with bifunctional cross-linker glutaraldhyde. The SiCS composite was characterized using FT-IR, SEM-EDAX, XRD and BET methods.

Preparation and characterization of La(III) encapsulated silica gel/chitosan composite and its metal uptake studies.

Lanthanum loaded silica gel/chitosan composite (LaSiCS) was prepared by mixing silica gel, LaCl(3) · 7H(2)O and chitosan which was then cross-linked with glutaraldhyde. The LaSiCS composite was characterized using FT-IR, SEM-EDAX, XRD and BET. The adsorption of chromium(VI) ions onto LaSiCS composite has been investigated.

WITHDRAWN: Preparation and characterization of silica gel/chitosan composite for the removal of Cu(II) and Pb(II).

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Removal of copper(II) using chitin/chitosan nano-hydroxyapatite composite.

Polymeric composites made up of nano-hydroxyapatite (n-HAp) with chitin and chitosan have been prepared and studied for the removal of Cu(II) ions from the aqueous solution. The sorption capacity (SC) of n-HAp, n-HAp/chitin (n-HApC) composite and n-HAp/chitosan (n-HApCs) composite were found to be 4.7, 5.

Preparation and metal uptake studies of modified forms of chitin.

Chitin (C), a biopolymer which showed moderate sorption capacity (SC) towards Cu(II) and Fe(III) was suitably modified to enhance the SC. Three types of modifications viz., protonated chitin (PC), carboxylated chitin (CC) and grafted chitin (GC) were carried out to increase the SC.

Preparation and application of alumina/chitosan biocomposite.

A new chitosan based biocomposite was prepared using alumina and used for the removal of chromium from the aqueous solution. The synthesized alumina/chitosan (AlCs) composite possesses an enhanced chromium sorption capacity (SC) of 8.62 mg/g than the original alumina and chitosan flakes that possess the SCs of 3.

Sorption of chromium(VI) using modified forms of chitosan beads.

Modified forms of chitosan beads were prepared and used for chromium removal from the aqueous solution. The prepared chitosan beads viz., protonated chitosan beads (PCB), carboxylated chitosan beads (CCB) and grafted chitosan beads (GCB) possess enhanced chromium sorption capacities (SCs) of 3239, 3647 and 4057 mg/kg respectively than the raw chitosan beads (CB) which possess the SC of 1298 mg/kg with a minimum contact time of 10min.