Low cost sorbents for the removal of methyl parathion pesticide from aqueous solutions.

Sorptive potential of selected agricultural waste materials i.e. rice (Oryza sativa) bran (RB), bagasse fly ash (BFA) of sugarcane (Saccharum officinarum), Moringa oleifera pods (MOP) and rice husk (RH) for the removal of methyl parathion pesticide (MP) from surface and ground waters has been investigated. Optimization of operating parameters of sorption process, i.e. sorbent dose, agitation time, pH, initial concentration of sorbate, and temperature have been studied. The sorption data fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) sorption isotherms. The maximum capacities of RB, BFA, MOP and RH for MP were calculated to be 3.6+/-0.8, 5.3+/-1.4, 5.2+/-1.5 and 4.7+/-1.0 mmolg(-1) by Freundlich, 0.39+/-0.009, 0.39+/-0.005, 0.36+/-0.004 and 0.35+/-0.008 mmolg(-1) by Langmuir and 0.9+/-0.08, 1.0+/-0.10, 1.0+/-0.10 and 0.9+/-0.07 mmolg(-1) by D-R isotherms respectively, employing 0.1g of each sorbent, at pH 6, 90 min agitation time and at 303 K. Application of first order Lagergren and Morris-Weber equations to the kinetic data yielded correlation coefficients, close to unity. Thermodynamic parameters of sorption process, i.e. DeltaH, DeltaS and DeltaG were computed and their negative values indicated the exothermic and spontaneous nature of sorption process. The pesticide may be stripped by sonication with methanol, making the regeneration and reutilization of sorbents promising. The sorbents investigated exhibited their potential applications in water decontamination, treatment of industrial and agricultural waste waters.

Sorption profile of Cd(II) ions onto beach sand from aqueous solutions.

Sorption of traces of Cd(II) ions onto beach sand is investigated as a function of nature and concentration of electrolyte (10(-4) to 10(-2)M nitric, hydrochloric and perchloric acids, pH 2-10 buffers and deionized water), shaking time 5-40min, shaking speed 50-200strokes/min, dosage of sand (50-1000mg/15cm(3)), concentration of sorbate (1.04x10(-6) to 1.9x10(-4)M) and temperature (293-323K). Maximum sorption of Cd(II) ions (approximately 66%) is achieved from deionized water using 300mg/15cm(3) sand in 20min. The data are successfully tested by Langmuir, Freundlich and Dubinin-Redushkevich (D-R) sorption isotherms. The values for characteristic Langmuir constants Q=13.31+/-0.20micromol/g and of b=(6.56+/-0.53)x10(3)dm(3)/mol, Freundlich constants A=2.23+/-1.16mmol/g and 1/n=0.70+/-0.05 of (D-R) constants beta=-0.005068+/-0.000328kJ(2)/mol(2), X(m)=46.91+/-11.91micromol/g and energy E=9.92+/-0.32kJ/mol have been estimated. Kinetics of sorption has been studied by applying Morris-Weber, Richenberg and Lagergren equations. The sorption follows first order rate equation resulting 0.182+/-0.004min(-1) The thermodynamic parameters DeltaH=32.09+/-2.92kJ/mol, DeltaS=111.0+/-9.5J/molK and DeltaG=-1.68+/-0.02kJ/mol are evaluated. The influence of common ions on the sorption of Cd(II) ions is also examined. Some common ions reduce the sorption while most of the ions have very little effect. It can be concluded that beach sand may be used as an alternative for the expensive synthetic sorbents.

The potential of cost-effective coconut husk for the removal of toxic metal ions for environmental protection.

Coconut (Cocos nucifera) husk, an agricultural waste, has been thoroughly investigated for the removal of toxic Cd(II), Cr(III) and Hg(II) ions from aqueous media. The parameters like nature and composition of electrolyte, concentration of toxic ions, dosage of coconut husk, and equilibration time between the two phases were optimized for their maximum accumulation onto the solid surface. The effect of common ions on the uptake of metal ions has been monitored under optimal conditions. The variation of retention of each metal ion with temperature was used to compute the thermodynamic quantities DeltaH, DeltaS and DeltaG. The values 18.1+/-0.6 kJmol(-1), 74+/-2 Jmol(-1)K(-1), and -3.8+/-0.04 kJmol(-1) at 298 K; 10.8+/-0.8 kJmol(-1), 48.8+/-2.7 Jmol(-1)K(-1), and -4.6+/-0.3 kJmol(-1) at 298 K; and -37.4+/-2k Jmol(-1), 105+/-7 Jmol(-1)K(-1) and -2.58+/-0.5 kJmol(-1) at 298 K were obtained for Cd(II), Cr(III) and Hg(II) ions, respectively. The sorption data were analysed by applying different sorption isotherms. The sorption capacity and energy were evaluated for each metal ion. The values of the Freundlich constants 1/n and C(m) were 0.92+/-0.04 and 52.6+/-22.2 mmolg(-1); 0.85+/-0.05 and 56.0+/-0.03 mmolg(-1); and 0.88+/-0.03 and 6.84+/-0.45 mmolg(-1) for Cd(II) Cr(III) and Hg(II) ions, respectively. Similarly, the Dubinin-Radushkevich (D-R) constants beta, X(m,) and E were evaluated for the three metal ions. To check the selectivity of the sorbent, sorption of a number of elements was measured under similar conditions. Separation of Zn(II) from Cd(II); Cr(III) from I(I), Zr(IV), Se(IV), and Hg(II) from Se(IV) and Zn(II) can be achieved using this sorbent. This cheap material has potential applications in analytical chemistry, water decontamination, industrial effluent treatment and in pollution abatement.

Sorptive potential of sunflower stem for Cr(III) ions from aqueous solutions and its kinetic and thermodynamic profile.

The sorptive potential of sunflower stem (180-300mum) for Cr(III) ions has been investigated in detail. The maximum sorption (>/=85%) of Cr(III) ions (70.2muM) has been accomplished using 30mg of high density sunflower stem in 10min from 0.001M nitric and 0.0001M hydrochloric acid solutions. The accumulation of Cr(III) ions on the sorbent follows Dubinin-Radushkevich (D-R), Freundlich and Langmuir isotherms. The isotherm yields D-R saturation capacity X(m)=1.60+/-0.23mmolg(-1), beta=-0.00654+/-0.00017kJ(2)mol(-2), mean free energy E=8.74+/-0.12kJmol(-1), Freundlich sorption capacity K(F)=0.24+/-0.11molg(-1), 1/n=0.90+/-0.04 and of Langmuir constant K(L)=6800+/-600dm(3)mol(-1) and C(m)=120+/-18micromolg(-1). The variation of sorption with temperature (283-323K) gives DeltaH=-23.3+/-0.8kJmol(-1), DeltaS=-64.0+/-2.7Jmol(-1)K(-1) and DeltaG(298k)=-4.04+/-0.09kJmol(-1). The negative enthalpy and free energy envisage exothermic and spontaneous nature of sorption, respectively. Bisulphate, Fe(III), molybdate, citrate, Fe(II), Y(III) suppress the sorption significantly. The selectivity studies indicate that Cr(III), Eu(III) and Tb(III) ions can be separated from Tc(VII) and I(I). Sunflower stem can be used for the preconcentration and removal of Cr(III) ions from aqueous medium. This cheaper and novel sorbent has potential applications in analytical and environmental chemistry, in water decontamination, industrial waste treatment and in pollution abatement. A possible mechanism of biosorption of Cr(III) ions onto the sunflower stem has been proposed.