Iron Oxide-coated Sand Research Articles

Adsorption-Dissolution Reactions Affecting the Distribution and Stability of CoIIEDTA in Iron Oxide-Coated Sand

The time-variant chemical behavior of Co[sup II]EDTA (and other metal-EDTA complexes) was investigated in suspensions of iron oxide-coated sand to identify equilibrium and kinetic reactions that control the mobility of Me[sup II]-EDTA complexes in subsurface environments. Batch experiments were conducted to evaluate the adsorption as a function of pH, concentration, and time and to quantify the rate-controlling step(s) of dissolution of the iron oxide by EDTA complexes. Ionic Co[sup 2+] exhibited typical cation-like adsorption, whereas Me[sup II]EDTA adsorption was ligand-like, increasing with decreasing pH. Adsorption isotherms for all reactive species exhibited Langmuir behavior, with site saturation occurring at molar values of <0.5% of Fe[sub tot]. The adsorption of Me[sup II]EDTA enhanced the apparent solubility of the iron oxide phase, which destabilized the Co[sup II]EDTA complex, liberating Co[sup 2+] and Fe[sup III]EDTA. The dissolution rate was an order of magnitude slower at pH 6.5 than at pH 4.5 and was influenced by the re-adsorption of solubilized Fe[sup III]EDTA. Two multireaction kinetic models were developed that each included Langmuir adsorption for Co[sup 2+] and metal-EDTA species but differed in their depiction of the dissolution mechanism (i.e., ligand-versus proton-promoted dissolution). 45 refs., 8 figs., 6 tabs.

A NOVEL TREATMENT OF DYE WASTEWATER OF BATIK INDUSTRY BY A COMBINATION OF ALUMINIUM SULFATE AND NATURAL IRON COATED-SAND

This paper presents the results of dye wastewater treatment of a batik industry in a batch experiment. Theexperiment was carried out by adding a mixture of aluminium sulfate as coagulant and natural iron oxide-coated sand (NICS) into the wastewater. Sedimentation rate of the formed flock was enhanced by a magnet. Initial COD concentration of the dye wastewater of 1060 mg/L was used in the experiment. Results of this research showed that the efficiency of the dye removal and settling time were affected by iron sandentrapped in the formed flocks. The highest efficiency of COD removal was 95%, or similar to the finalCOD concentration of 45 mg/L at settling time of 10 minutes. It could be concluded that the combination ofaluminium sulfate and NICS could effectively be used in the treatment of the dye wastewater from batikindustry.