Treatment of Cyanide Bearing Water/Wastewater by Plain and Biological Activated Carbon

Phytoremediation of cyanide containing steel industrial wastewater by Eichhornia crassipes

Water pollution has become one of the serious problems of today's civilization. Free cyanide and complex cyanide, including HCN and CN^- is the most reactive and toxic substance of all industrial pollutants. R&D, Tata Steel preliminary investigation reports have established that cyanide in the blast furnace (BF) blows down water above permissible limit. Presently, chemical treatment has been applied to attenuate the cyanide level 0.2 ppm (permissible limit of free cyanide as per environmental norms). From the economic point of view, phytoremediation could be an attractive technology in dealing with this dangerous pollutant. Cyanide BF blow down water could possibly be removed by the water hyacinth because of its high biomass production, and tolerance to cyanide (CN). This investigation is related to the study of the potential of water hyacinth on the cyanide ion pollutant removal from BF water using cost-effective biological technology-Phytoremediation. The experimental results have shown that about 95% removal of cyanide from blast furnace water could be achieved by water hyacinth in 3 days in 6 L and also in 100 L water. Water hyacinth is also effective for reducing biochemical oxygen demand (BOD) and chemical oxygen demand (COD). This aquatic plant is also capable of reducing ammonia, TDS, and hardness of water.

Subchronic cyanide toxicity on male reproductive system of albino rat

Sexually mature albino rats were orally treated with sodium cyanide, NaCN (0, 0.64, 1.2 and 3.2 mg kg⁻¹BW) for 90 days.

Kinetics and pathways of cyanide degradation at high temperatures and pressures

The degradation of cyanide was performed in a 1-L semibatch reactor at temperatures between 393 and 473 K and at total pressures in the range of 2.0-8.0 MPa. The initial pH of the solution was set at 11, whereas initial concentrations ranged from 3.85 to 25 mM, which resemble the typical concentrations of cyanide-containing wastewater. The change with time of cyanide concentration, intermediates, and final products was analyzed in order to elucidate the reaction pathways. The experimental results suggest two parallel pathways of alkaline hydrolysis for the degradation of the pollutant. Formate and ammonia were identified as the final reaction products for one of the pathways, whereas carbon dioxide, nitrogen, and hydrogen were considered to be the final products for the other one. The degradation reaction results were fitted to first-order kinetic equations with respect to cyanide, giving respectively activation energies of 108.2 ± 3.3 and 77.6 ± 3.0 kJ/mol. Consequently, the formation of formate and ammonia is favored at high temperatures, whereas low temperatures favored the pathway leading to the formation of carbon dioxide and nitrogen.

Enhanced carbon adsorption treatment for removing cyanide from coking plant effluent

Batch experiments were conducted to determine the effects of metal loading and fixing methods on the capacity of granular activated carbon (GAC) for removing cyanide from KCN (pH 11), K(3)Fe(CN)(6) solutions and several SCP effluent samples. KI fixed carbon (Cu/KI-GAC) was the most effective among the GAC samples tested. Adsorption was the primary mechanism of cyanide removal; catalytic oxidation of the adsorbed cyanide on carbon surface contributed a minor amount of the observed removal. Four small adsorbers containing the base GAC and 0-100% of Cu/KI-GAC were employed for treating a Fenton oxidized/precipitated SCP effluent sample. After the start-up period (<3-week) to establish the effective biological activated carbon (BAC) function in the adsorbers, the effluents became stable and met the discharge limits (COD(Cr)<50mg/L and TCN<0.5mg/L); with >30% Cu/KI-GAC in the adsorber, the effluent would meet the discharge limits during the start-up phase.