Adsorptive separation of copper, nickel, lead, zinc and cadmium from aqueous solution using MWCNTs impregnated with D2EHPA and prior to their determination by FAAS: Kinetic and equilibrium studies

Adsorptive detoxification of Cd2+ and Pb2+ from wastewater using MWCNTs functionalized with -di-(2-ethyl hexyl phosphoric acid) and bis-(2,4,4-trimethyl pentyl) phosphonic acid

Selective and rapid determination of procedure for Cd2+ and Pb2+ samples using MWCNT surfaces can be modified by loading ligands such as D2EHPA and Cyanex 272 which is described. The adsorbent was modified with D2EHPA and Cyanex 272. Effect of pH, amount of adsorbent, contact time for adsorption, and the optimum eluent for the quantitative recovery of Cd2+ and Pb2+ were investigated and the subsequent determination by FAAS. The adsorption was found to be mainly due to the chemical interactions between the metal ions and functional groups -COO- and -OH which were characterized by FT-IR. The adsorption of metal occurs at pH 4.5 with 500 mg of MWCNTs. The enrichment factor was 40 and 30. The detection limit was 0.03 and 0.05 μg L-1. The quantitative recovery of metal ion used 1 mol L-1 HNO3. The thermodynamic parameter of Langmuir and Freundlich adsorption isotherm revealed that the adsorption of free energy (ΔG) was spontaneous and the monolayer adsorption of Cd2+ and Pb2+ was mainly on the surfaces. The adsorbent performance of R2 in the range of 0.93-0.99 and also the identified adsorption efficiency of Cd2+ and Pb2+ are linear or non-linear curves respectively. The proposed method was applied to heavy metals from environmental samples.

Development of Armillae mellea immobilized nanodiamond for the preconcentrations of Cr(III), Hg(II) and Zn(II)

In this study, we present an environmental friend and easy procedure for simultaneous preconcentration of Cr(III), Hg(II) and Zn(II) by solid-phase extraction before their determination by inductively coupled plasma optical emission spectrometry. Armillae mellea immobilized nanodiamond was used as sorbent. During the study, critical parameters influencing the extraction performance were investigated in detail. The best parameters were found as pH 5.0, 2.0 mL min^-1 of flow rate, 200 mg of Armillae mellea, 300 mL of sample volume. LOD values were found as 0.025, 0.13 and 0.038 ng mL^-1, respectively for Cr(III), Hg(II) and Zn(II). By applying the developed procedure, sensitivities of ICP-OES were improved for 60 fold for Cr(III), Hg(II) and Zn(II). Their concentrations in different food samples were measured after microwave digestion and solid-phase extraction.

Sorption and Desorption Studies of Pb(II) and Ni(II) from Aqueous Solutions by a New Composite Based on Alginate and Magadiite Materials

A new composite material based on alginate and magadiite/Di-(2-ethylhexyl) phosphoric acid (CAM-D2EHPA) was successfully prepared by previous impregnation of layered magadiite with D2EHPA extractant, and then immobilized into the alginate matrix. Air dried beads of CAM-D2EHPA were characterized by FTIR and SEM⁻EDX techniques. The sorbent was used for the separation of lead and nickel from nitrate solutions; the main parameters of sorption such as contact time, pH of the solution, and initial metal concentration were studied. The beads recovered 94% of Pb(II) and 65% of Ni(II) at pH 4 from dilute solutions containing 10 mg L-1 of metal (sorbent dosage, S.D. 1 g L-1). The equilibrium data gave a better fit using the Langmuir model, and kinetic profiles were fitted using a pseudo-second order rate equation. The maximum sorption capacities obtained (at pH 4) were 197 mg g-1 and 44 mg g-1 for lead and nickel, respectively. The regeneration of the sorbent was efficiently carried out with a dilute solution of HNO₃ (0.5 M). The composite material was reused in 10 sorption⁻elution cycles with no significant differences on sorption uptake. A study with synthetic effluents containing an equimolar concentration of both metals indicated a better selectivity towards lead ions.

Effect of MWCNT-modified graphite felts on hexavalent chromium removal in biocathode microbial fuel cells

Oxidized MWCNT-modified graphite felt significantly improved Cr(vi) removal in biocathode MFCs due to its affinity towards microbes and Cr(vi).