C. Raji

Bio: C. Raji is an academic researcher from University of Kerala. The author has contributed to research in topics: Adsorption & Langmuir adsorption model. The author has an hindex of 4, co-authored 5 publications receiving 840 citations.

Removal of heavy metal ions from water using sawdust-based activated carbon

Abstract: The removal of Pb(II), Hg(II) and Cd(II) by activated carbon prepared from bicarbonate-treated rubber wood sawdust has been found to be concentration, pH and temperature dependent. The percentage adsorption of metal ions increased with decrease in initial concentration of metal ions, increase in adsorbent dosage and temperature. The optimum pH range for the removal of ~b(II) and Hg(II) is 4-8 whereas maximum uptake for Cd(II) is in the pH range 5-9. The applicability of Lagergren kinetic model has also been investigated. The equilibrium data at different temperatures fit well with the Langmuir isotherm. Thermodynamic constant (Ko) and standard free energy (t.GO), enthalpy (M?) and entropy (&5°) changes were calculated for predicting the nature of adsorption. The surface mass transfer coefficient as a function of initial adsorbate concentration has been determined. Desorption studies revealed that spent adsorbent can be regenerated and reused by 0.2 M HC!. The presence of heavy metals in the environment can be detrimental to a variety of living species. Therefore, the elimination of heavy metals from water and wastewater is important to protect public health. Many reports have appeared on the development of activated carbon from cheaper and readily available materials for the removal of metals from water':'. Activated carbon derived from rice husk', coconut shell", waste slurry generated from fertilizer plant', peanut huW' and waste tea leaves" has been successfully employed for the removal of heavy metals from aqueous solutions. Our search for a cheap readily available starting material has identified sawdust as a potentially attractive material for the production of activated carbon for water treatment. Sawdust is a cheap raw material and in abundant supply. The huge deposit of sawdust around sawmills poses problems in its disposal. Besides its utilization in preparing packing materials it has also been recently used in water pollution control"!". The present investigation aims at using bicarbonate treated activated carbon prepared from sawdust, a low cost and highly effective adsorbent for the removal of hea vy metals namely Pb(II), Hg(II) and Cd(I1) from aqueous systems.

Batch metal removal by modified hydrous titanium (IV) oxide gel : Kinetics and thermodynamics

Abstract: The adsorption ability of polyacrylamide grafted hydrous titanium(lV) 'Oxidegel for heavy metals in aqueous solutions has been investigated by means of batch adsorption tests. The adsorbent material on IR spectral characterization showed the presence of peripheral - COOH group and exhibits a very high adsorption potential for Pb(II), Hg(II) and Cd(II). Kinetic measurements have been made as a function of agitation time, initial metal concentration, adsorbent dose, pH and temperature. The process follows a first - order kinetics. The intraparticie diffusion of metal ions through pores in the adsorbent was shown to be the main rate limiting step. The sorbent is effective for the quantitative removal of metal ions at pH 6.0. Temperature dependence indicates the endothermic nature of the process. A Langmuir isotherm model fits the equilibrium data well. Thermodynamic parameters were ,calculated for predicting the nature of adsorption. The method was applied for synthetic wastewaters. Acid regeneration of the adsorbent has been tried. The processes developed to remove heavy metals from wastewater include chemical precipitation, coagulation, complexing, solvent extraction, ion exchange and adsorption. At low concentrations, the removal of such pollutants is more effective by ion exchange or adsorption on solid adsorbents. Different types of polymeric materials and synthetic resins are used as adsorbents for the removal of metal pollutants from chemical process industries in certain developed countries'. Surface modifications by chemical treatment of the adsorbent materials usually improve the physical characteristics and adsorption efficiency of the adsorbents=', Silica gel modified with pyridinium ions' and clay impregnated with 2mercaptobenzothiazol' have been developed for the adsorption of heavy metals from water. Formaldehyde polymerized onion skin", tree bark', tea leaves" and sawdust" were also used as adsorbents for heavy metals. Previous research has suggested that polymer coated metal oxide gels represent a new and promising class of sorbent materials for the removal of heavy metals from waste waters. The materials such as silica gel'", iron (III) oxide!', tin *For correspondence

Citation review of Lagergren kinetic rate equation on adsorption reactions

Abstract: This study presents a literature review concerning the preciseness of over 170 publications citing the original Lagergren's paper in kinetics equation for solute adsorption on various adsorbents. This equation applies to a range of solid-liquid systems such as metal ions, dyestuffs and several organic substances in aqueous systems onto various adsorbents. The main objectives are to manifest different forms of citations presented and offers a correct reference style for citing the original Lagergren's paper published in 1898.

Agricultural residues as precursors for activated carbon production—A review

Abstract: A review of the production of activated carbons from agricultural residues is presented. The effects of various process parameters on the pyrolysis stage are reviewed. Influences of activating conditions, physical and chemical, on the active carbon properties are discussed. Under certain process conditions several active carbons with BET surface areas, ranging between 250 and 2410 m 2 /g and pore volumes of 0.022 and 91.4 cm 3 /g, have been produced. A comparison in characteristics and uses of activated carbons from agricultural residues with those issued from tires, and commercial carbons, have been made. A review is carried out of the reaction kinetic modelling, applied to pyrolysis of agricultural wastes and activation of their pyrolytic char.