Preparation, characterization of cellulose-grafted with calix[4]arene polymers for the adsorption of heavy metals and dichromate anions

Remediation technologies for heavy metal contaminated groundwater

The contamination of groundwater by heavy metal, originating either from natural soil sources or from anthropogenic sources is a matter of utmost concern to the public health. Remediation of contaminated groundwater is of highest priority since billions of people all over the world use it for drinking purpose. In this paper, thirty five approaches for groundwater treatment have been reviewed and classified under three large categories viz chemical, biochemical/biological/biosorption and physico-chemical treatment processes. Comparison tables have been provided at the end of each process for a better understanding of each category. Selection of a suitable technology for contamination remediation at a particular site is one of the most challenging job due to extremely complex soil chemistry and aquifer characteristics and no thumb-rule can be suggested regarding this issue. In the past decade, iron based technologies, microbial remediation, biological sulphate reduction and various adsorbents played versatile and efficient remediation roles. Keeping the sustainability issues and environmental ethics in mind, the technologies encompassing natural chemistry, bioremediation and biosorption are recommended to be adopted in appropriate cases. In many places, two or more techniques can work synergistically for better results. Processes such as chelate extraction and chemical soil washings are advisable only for recovery of valuable metals in highly contaminated industrial sites depending on economical feasibility.

Succinate-bonded cellulose: a regenerable and powerful sorbent for cadmium-removal from spiked high-hardness groundwater

The primary objective of this work was to evaluate a chemically modified cellulose for the sorption efficiency and selectivity to remove cadmium from spiked high-hardness groundwater. Heterogeneous esterification of cellulose with succinic anhydride in toluene under basic conditions has proceeded very efficiently to yield the succinylated cellulose (SC) with fairly high DS value, as confirmed by FTIR and solid-state MAS (13)C NMR spectroscopies. Deprotonation of the free carboxylic acid group was achieved by alkaline treatment of SC with saturated NaHCO(3) aqueous solution. Batch experiments were carried out on the resulting sodic material (NaSC) to examine its cadmium-removing capability in both distilled water (DW) and spiked groundwater (GW). The results obtained from the sorption characteristics (kinetics, isotherms and pH effect) have revealed that NaSC material is particularly effective in removing cadmium from both DW and GW solutions, with a maximum uptake of 185.2 and 178.6 mg g(-1), respectively. These comparable sorption capacities strongly suggest that NaSC sorbent is highly selective to heavy metal over alkaline earth cations (Ca(2+) and Mg(2+)) and therefore less susceptible to interference from background ions, naturally present in groundwater. On the other hand, cadmium sorption is shown to decrease with a decrease in pH which is indubitably inherent to the competing proton during the ion-exchange process. Furthermore, the material has proven to be efficiently regenerable by using a NaCl brine solution. Thus, the use of the sorbent sequentially to the first regeneration led to nearly no attenuation in the material's capacity for cadmium-removal. Finally, the sorption effectiveness of NaSC is compared to those of other low-cost sorbents so far reported in the literature.

Preparation of p-tert[(dimethylamino)methyl]-calix[4]arene functionalized aminopropylpolysiloxane resin for selective solid-phase extraction and preconcentration of metal ions

A new p-tert-[(dimethylamino)methyl]-1,3-bisglyciyl-calix[4]arene functionalized aminopropylpolysiloxane resin (APPS-CA) has been prepared and investigated for selective solid-phase extraction (SPE) of trace Cr (III), Cu (II), Ni (II), Co (II) and Zn (II) prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The characterization of the surface modification was performed on the basis of FT-IR spectroscopy, elemental analysis and thermal gravimetric analysis. The separation/preconcentration conditions of analytes were investigated, including effect of pH, the shaking time, the sample flow rate and volume, the elution condition, the interfering ions and stability test. At pH 4.0, the maximum adsorption capacity of Cr (III), Cu (II), Ni (II), Co (II) and Zn (II) were 47.2, 34.3, 52.8, 29.8 and 36.4 mg g(-1), respectively. The adsorbed metal ions were quantitatively eluted by 2.0 mL of 0.5 mol L(-1) HCl. Common coexisting ions did not interfere with the separation. According to the definition of International Union of Pure and Applied Chemistry, the detection limits (3 sigma) of this method were found to be 0.58, 0.33, 0.47, 0.61 and 0.14 ng mL(-1) for Cr (III), Cu (II), Ni (II), Co (II) and Zn (II), respectively. The relative standard deviation under optimum conditions is less than 4.0%. The application of this new adsorbent to preconcentration trace Cr (III), Cu (II), Ni (II), Co (II) and Zn (II) of two water samples gave high accurate and precise results.

Solid-phase extraction of copper, iron and zinc ions on Bacillus thuringiensis israelensis loaded on Dowex optipore V-493

Bacillus thuringiensis israelensis loaded on Dowex optipore V-493 as new adsorbent for the separation-preconcentration of heavy metal ions has been proposed. The analytical conditions for the quantitative recoveries of copper(II), iron(III) and zinc(II) including pH, amounts of adsorbent, sample volume, etc. were investigated. The influences of alkaline and earth alkaline ions were also reported. The recovery values for the analytes are generally higher than 95%. The preconcentration factor was 37. The limit of detections of the analyte ions (k=3, N=21) were 1.14 microgL(-1) for copper, 2.01 microgL(-1) for iron and 0.14 microgL(-1) for zinc. The relative standard deviations of the determinations were found to be lower than 9%. The procedure was validated by analyzing copper, iron and zinc contents in two certified reference materials, NRCC-SLRS-4 Riverine water and NIST SRM 1515 Apple leaves. Agreements between the obtained results and the certified values were achieved. The developed preconcentration method was applied in the flame atomic absorption spectrometric determination of copper, iron and zinc in several samples including a multivitamin-multimineral tablet, dialysis solutions, natural waters and some food samples.