Bina Gupta

A comparative investigation on adsorption performances of mesoporous activated carbon prepared from waste rubber tire and activated carbon for a hazardous azo dye—Acid Blue 113

A mesoporous carbon developed from waste tire rubber, characterized by chemical analysis, FTIR, and SEM studies, was used as an adsorbent for the removal and recovery of a hazardous azo dye, Acid Blue 113. Surface area, porosity, and density were determined. The adsorption of the dye over the prepared adsorbent and a commercial activated carbon was achieved under different pH, adsorbate concentration, sieve size, adsorbent dosage, contact time and temperature conditions. Langmuir and Freundlich adsorption isotherm models were applied and thermodynamic parameters were calculated. Kinetic studies indicated that the adsorption process follow first order kinetics and particle diffusion mechanisms are operative. By percolating the dye solution through fixed-bed columns the bulk removal of the Acid Blue 113 was carried out and necessary parameters were determined to find out the percentage saturation of both the columns. Recovery of the dye was made by eluting 0.1 M NaOH through the column.

Pesticides removal from waste water by activated carbon prepared from waste rubber tire

Waste rubber tire has been used for the removal of pesticides from waste water by adsorption phenomenon. By applying successive chemical and thermal treatment, a basically cabonaceous adsorbent is prepared which has not only a higher mesopore, macropore content but also has a favorable surface chemistry. Presence of oxygen functional groups as evidenced by FTIR spectra along with excellent porous and surface properties were the driving force for good adsorption efficiency observed for the studied pesticides: methoxychlor, methyl parathion and atrazine. Batch adsorption studies revealed maximum adsorption of 112.0 mg g(-1), 104.9 mg g(-1) and 88.9 mg g(-1) for methoxychlor, atrazine and methyl parathion respectively occurring at a contact time of 60 min at pH 2 from an initial pesticide concentration of 12 mg/L. These promising results were confirmed by column experiments; thereby establishing the practicality of the developed system. Effect of various operating parameters along with equilibrium, kinetic and thermodynamic studies reveal the efficacy of the adsorbent with a higher adsorption capacity than most other adsorbents. The adsorption equilibrium data obey Langmuir model and the kinetic data were well described by the pseudo-first-order model. Applicability of Banghams equation indicates that diffusion of pesticide molecules into pores of the adsorbent mainly controls the adsorption process. Spontaneous, exothermic and random characteristics of the process are confirmed by thermodynamic studies. The developed sorbent is inexpensive in comparison to commercial carbon and has a far better efficiency for pesticide removal than most other adsorbents reported in literature.

Extraction and recovery of cadmium using Cyanex 923

Studies have been carried out in the extraction of Cd(II) along with Al(III), Fe(III), In(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Hg(II) and Pb(II) from hydrochloric acid medium using Cyanex 923. The effect of different variables influencing the extraction of Cd(II) such as the concentration of acid, metal ion and extractant and the nature of the diluent has been investigated. The extracting species of Cd(II) is proposed. Based on the partition data, some binary separations of topical interest from Cd(II) have been achieved. The potential of the extractant for the recovery of pure cadmium from some zinc and copper matrices is assessed.

Extraction of uranium, thorium and lanthanides using Cyanex-923: Their separations and recovery from monazite

The extraction behavior of uranium, thorium and lanthanides, represented by cerium and ytterbium, by Cyanex-923 has been investigated. The effect of different variables like the concentration of acids, metal ion and extractant, nature of diluent and temperature has been studied. A composition for the extracted U(VI) and Th(IV) species has been proposed. Based on the partition data some important binary and ternary separations involving the aforesaid metal ions have been achieved. The proposed procedure has been applied for the recovery of uranium, thorium and lanthanide fraction from monazite sand. The stability and regeneration capacity of the extractant have been evaluated.

Recovery of cobalt, nickel, and copper from sea nodules by their extraction with alkylphosphines

The paper describes a process for the recovery of pure Co(II), Ni(II), and Cu(II) from a hydrochloric acid solution of polymetallic sea nodules. An overnight contact of the nodule powder with 4 M HCl almost quantitatively leaches these metal ions. From the leachate, Co(II) and Cu(II) were recovered by their extraction with Cyanex 923 and Ni(II) by extraction with Cyanex 301. Co(II) and Cu(II) are partitioned in the organic phase as H2CoCl4·2 Cyanex 923 and CuCl2·2 Cyanex 923, whereas Ni(II) is extracted in the form of NiR2 (HR=Cyanex 301). A solution of 0.001 M H2SO4 is used for the stripping of Co(II) and Cu(II) and 5% NH4Cl in 75% NH3 for Ni(II). Both extractants are found to be stable toward prolonged contact with HCl and show negligible loss in their extraction capacity even after recycling them for 20 cycles. The partition data have been utilized in developing conditions for the separation of Co(II), Ni(II), and Cu(II) mutually and from other metal ions, namely Ti(IV), Al(III), Fe(III), Mn(II), and Zn(II). The procedure of separation thus developed has been extended for the recovery of around 90% Co(II), Ni(II), and Cu(II) from sea nodules. The purity of the metal ions thus obtained is around 99%.

Solvent Extraction and Separation of Tervalent Lanthanides and Yttrium Using Cyanex 923

Abstract The paper embodies extraction behavior of some tervalent lanthanides [La, Ce, Nd, Eu, Gd, Ho, Yb] along with Y(III) from HNO3, HCl, H2SO4, and H3PO4 media in a toluene solution of Cyanex 923. The effect of some important variables like equilibration time, nature of diluent and the concentration of acid, extractant and metal ion on the extraction is investigated. Based on the partition data the stoichiometry of the extracting species is formulated as Ln(NO3)3·2Cyanex 923. The reagents like 5.0 mol L−1 HNO3, 0.5 mol L−1 H2SO4/HCl and 1.0 mol L−1 H3PO4 have been found effective for stripping of the metal ions. Cyanex 923 is stable even after prolonged acid contact and the extraction efficiency remains unaffected even after 20 recycling steps. Based on the partition data the lanthanides can be divided into four distinct groups namely light (La, Ce, Nd), middle (Eu, Gd), holmium (Ho), and heavy (Yb). The separation factors indicate that the separation of light and heavy fractions can be conveniently achieved from all the four investigated acid media. However, the separation of lanthanides into the said four fractions is more apparent from nitric acid medium. The data have been successfully employed for the separation of lanthanides and yttrium in different fractions from a synthetic mixture.

Degradation of thiram in water, soil and plants: a study by high-performance liquid chromatography

A comprehensive study was conducted to evaluate the persistence of thiram in water and soil under controlled conditions and on two plants, namely tomato and radish, in field conditions. In order to follow the decay of the pesticide, an HPLC procedure was developed employing an octadecyl endcapped RP-C18 column using a mixture of acetonitrile and water as the mobile phase and an ultraviolet detector. Studies conducted in water at different temperature, pH and organic content revealed that the persistence of the pesticide decreases with the increase in all the three variables. In the three different types of soils studied, the effect of pH was more or less apparent on a similar line. On average a slower decay was observed in the case of plants than in water and soil.

Extraction and separation of nickel(II) using bis(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex 301) and its recovery from spent catalyst and electroplating bath residue

ABSTRACT The paper embodies the details on the extraction behaviour ofNi(II) along with Cr(III), Fe(ni), Mn(II), Co(II), Cu(II) and Zn(II) from sulfuric acid media employing Cyanex 301-toluene system. The effect of various parameters like concentration of acid, metal ion and extractant and nature of diluent on the extraction of Ni(II) has been studied. On the basis of the distribution data the extracting species has been proposed. The recycling capacity of the extractant has been assessed. Some binary and ternary separations have also been achieved. The practical utility of the extractant has been demonstrated by recovering Ni(II) from spent catalyst and electroplating bath residue.

Decay profile and metabolic pathways of quinalphos in water, soil and plants

The widespread occurrence of pesticide residues in different agricultural and food commodities has raised concern among the environmentalists and food chemists. In order to keep a proper track of these materials, studies on their decay profiles in the various segments of ecosystem under varying environmental conditions are needed. In view of this, the metabolites of quinalphos in water and soil under controlled conditions and in plants, namely tomato and radish in field conditions have been analysed and possible pathways suggested. In order to follow the decay of the pesticide, an HPLC procedure has been developed. Studies conducted in water at different temperatures, pH and organic content reveal that the persistence of the pesticide decreases with the increase in all the three variables. In the three different types of soils studied, the effect of pH is more or less apparent on a similar line. On an average a faster decay is observed in the case of plants than in water and soil. The decay profiles in all these cases follow first order kinetics. The metabolites were identified by GC-MS. The investigations reflect that degradation occurs through hydrolysis, S-oxidation, dealkylation and thiono-thiol rearrangement. The pathways seem to be complex and different metabolites were observed with the change in the matrix. Quinalphos oxon, O-ethyl-O-quinoxalin-2-yl phosphoric acid, 2-hydroxy quinoxaline and quinoxaline-2-thiol were observed in all the matrices. Results further indicate that the metabolites, 2-hydroxy quinoxaline and oxon, which are more toxic than parent compound, persist for a longer time.

EXTRACTION AND SEPARATION OF SOME 3d TRANSITION METAL IONS USING CYANEX 923

The paper embodies details on the extraction of different 3d transition metal ions namely Ti(IV), V(IV), Cr(III), Fe(III), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) in a toluene solution of Cyanex 923 from different mineral acid media. Effect of some important parameters such as the concentration of extractant and metal ion and nature of the diluent on the partition of Ti(IV), V(IV), Fe(III), Cu(II) and Zn(II) is examined. The extracting species of these metal ions are proposed and the loading capacity of Cyanex 923 is checked. The hydrolytic stability of the extractant solution has been examined and a procedure developed for its recycling. The extraction behavior of a number of commonly associated elements like Ce(IV), Al(III), Ga(III), Mg(II), Cd(II) and Pb(II) encountered in some of the matrices has also been investigated. Based on the distribution data it has been possible to achieve various binary separations of analytical interest involving 3d transition metal ions.