methods of nickel removal from valerian irrigating waste water

industrial development and extensive use of heavy metals have led to the problem of environmental pollution. nickel compounds are toxic to plants and have detrimental effects on their growth. valerian is a plant used in herbal medicine. considering the hazards of nickel, various methods have been developed to remove this contaminant from herbs irrigation wastewater, including the common chemical precipitation and the novel electrocoagulation methods. an advantage of electrocoagulation is its high efficiency in removal of contaminants. in this study, nickel at a concentration of 500 mg/l in a synthetic wastewater was removed by chemical precipitation with sodium hydroxide, lime, and sodium sulfide, as well as by electrocoagulation; the removal efficacy was 80.66%, 78.92%, 86.02 and 99.96, respectively. the pilot used for electrocoagulation was made of plexiglass with 10 metallic electrodes of 11×7×0.2 cm. comparison of the results showed high efficiency of electrocoagulation. in these experiments, ph was considered about 6.