REMOVAL OF ARSENIC FROM AQUEOUS-SOLUTION BY ADSORBING COLLOID FLOTATION

Adsorbing colloid flotation (ACF) with ferric hydroxide as the copreci pitant, anionic surfactant sodium dodecyl sulfate (SDS) as the collect or, and nitrogen microbubbles has been shown to be effective in removi ng arsenic from low concentration of arsenic aqueous solution (approxi mately 10 mg/dM3). Experiments were conducted to assess the effects of pH, dosages of SDS and Fe(III), gas flow rate, foreign anions includi ng NO3-, SO42-, and PO43-, and Al(III) addition on the efficiency of t he arsenic removal by ACF. When pH is at the range of 4-5,99.5 % arsen ic removal efficiency can be achieved. The optimal operating condition s are 35 ppm SDS, 80 ppm Fe(III), 40 cm3/min gas flow rate, 500 rpm ro tary speed of stirrer, and 5 min ferric hydroxide floc formation time. The analysis results indicate that foreign anions SO42- and PO43- hav e an inhibiting effect on the removal of arsenic, while AI(III) additi ons can compensate for the effect. An actual mine wastewater sample co ntaining 10.4 ppm arsenic(V), 0.76 ppm chromium(VI), and 0.55 ppm lead was tested by adsorbing colloid flotation at the optimal operation co nditions. The residual arsenic, chromium, and lead are 0.07, 0.06, and 0.04 ppm, respectively. The interaction mechanisms between Fe(OH)3-be aring arsenic floc and SDS were analyzed and interpreted by means of z eta-potential, infrared spectra analysis, and molecular orbital theory . The adsorption of SDS can occur physically and chemically on Fe(OH)3 at the pH range of 4-5.