Authors:S. Husaini, J. Zaidi, Matiullah, and M. Akram
The industrial pollution is exponentially growing in the developing countries due to the discharge of untreated effluents
from the industries in the open atmosphere. This may cause severe health hazards in the general public. To reduce this effect,
it is essential to remove the toxic and heavy metals from the effluents before their disposal into the biosphere. In this
context, samples of the effluents were collected from the textile/yarn, ceramics and pulp/paper industries and the concentrations
of the toxic metal ions were determined using neutron activation analysis (NAA) technique. The observed concentration values
of the As, Cr and Fe ions, in the unprocessed industrial effluents, were 4.91 ± 0.8, 9.67 ± 0.7 and 9.71 ± 0.8 mg/L, respectively
which was well above the standard recommended limits (i.e. 1.0, 1.0 and 2.0 mg/L, respectively). In order to remove the toxic metal ions from the effluents, the samples were treated with pea nut husk fence.
After this treatment, 91.5% arsenic, 81.9% chromium and 66.5% iron metal ions were successfully removed from the effluents.
Then the treated effluents contained concerned toxic metal ions concentrations within the permissible limits as recommended
by the national environmental quality standards (NEQS).
The sorption of hafnium on hydrous titanium oxide (TiO2·1.94 H2O) has been studied in detail. Maximum sorption of hafnium can be achieved from a pH 7 buffer solution containing boric acid and sodium hydroxide using 50 mg of the oxide after 30 minutes shaking. The value ofkd, the rate constant of intraparticle transport for hafnium sorption, from 0.01M hydrochloric and perchloric acid and pH 7 buffer solutions has been found to be 17 mmole·g–1·min–2. The kinetics of hafnium sorption follows Lagergren equation in 0.01M HCl solution only. The values of the overall rate constantK
=6.33·10–2 min–1 and of the rate constant for sorptionk1=6.32·10–2 min–1 and desorptionk2=2.28·10–5 min–1 have been evaluated using linear regression analysis. The value of correlation factor() is 0.9824. The influence of hafnium concentration on its sorption has been examined from 4.55·10–5 to 9.01·10–4 M from pH 7 buffer solution. The sorption data followed only the Langmuir sorption isotherm. The saturation capacity of 9.52 mmole·g–1 and of a constant related to sorption energy have been estimated to be 2917 dm3·mole–1. Among all the additional anions and cations tested only citrate ions reduce the sorption significantly. Under optimal experimental conditions selected for hafnium sorption, As(III), Sn(V), Co(II), Se(IV) and Eu(III) have shown higher sorption whereas Mn(II), Ag(I) and Sc(III) are sorbed to a lesser extent. It can be concluded that a titanium oxide bed can be used for the preconcentration and removal of hafnium and other metal ions showing higher sorption from their very dilute solutions. The oxide can also be employed for the decontamination of radioactive liquid waste and for pollution abatement studies.