Hydrology: Current Research

The adsorption of phenol and lead (II) onto granular activated carbon (GAC) in single and binary system has been studied using fixed bed adsorber. A general rate multi-component model has been utilized to predict the fixed bed breakthrough curves for dual-component system. This model considers both external and internal mass transfer resistances as well as axial dispersion with non-liner multi-component isotherm. The effect of important parameter, such as flow rate, bed height and initial concentration on the behavior of breakthrough curves have been studied. The equilibrium isotherm Model parameters such as isotherm model constants, pore diffusion coefficients (Dp) were obtained from batch experiments, while the external mass transfer coefficients and axial dispersion (kf, Dz) were calculated from empirical correlations. The results shows that the general rate model was found suitable for describing the adsorption process of the dynamic behavior of the GAC adsorber column.

Alumina was synthesized by surface hydrolysis of thin aluminium plate and then applied as an adsorbent to treat the refinery effluent water to reduce the levels of COD(Chemical Oxygen Demand), BOD(Biological Oxygen Demand) and OG(Oil and Grease) content in the effluent to satisfy the prescribed limit. The prepared alumina was characterized based on BET surface area, X-ray diffraction analysis and scanning electron microscopy. The effects of the amount of adsorbent, temperature and the dilution of the effluent on the reduction of COD, BOD and OG levels were studied. COD, BOD and OG reduction were observed to be 87.83%, 86.6% and 83% at 20°C with an alumina dose of 15 gms per 100 ml effluent. In the equilibrium study, it has been noted that the adsorption capacities of alumina for COD and OG at equilibrium are linearly co-related. The adsorption is of first order and the initial rate constant obtained is 3×10-6 min-1 at 20°C.

The presence of heavy metals in industrial effluents as a single component is generally very rare. The present study provides information about adsorption behaviour of lead, cadmium and copper in single and multi-component system using triticum aestivum (wheat straw) as adsorbent. It has been shown that adsorption of a certain metal ion is greatly affected by the presence of other metal ions. Effects of process parameters (adsorbent dose, contact time, pH, agitation speed etc.) have been studied. pH 4-6 have been found suitable for metal removal. Adsorption mechanism has been evaluated using five adsorption isotherm models (Langmuir, Freundlich, Temkin, Harkin- Jura and Halsey Isotherms). Removal of cadmium in multi-component system is greater as compared in single component system indicating the metal competition for adsorption sites. Kinetic and thermodynamic parameters have also been calculated and obtained results were found closely related to the reported literature. Positive values of ?H° for lead, cadmium and copper shows feasibility of the process and the spontaneous nature of adsorption.