Adsorption Properties Of Modified Steel Slag For Removal Of Mercury And Arsenic From Seawater

Mercury and arsenic represent heavy metal pollutants in the Chinese coastalwaters. They may bio-accumulate through the food chain, disrupt normal circadianphysiological and behavioral rhythms of marine life, and are potentially toxic tohumans. In foreign countries, it becomes a trend that using industrial waste as anadsorbent for removal of heavy metal from aqueous solution. Steel slag is the wastegenerated in the steelmaking process. It is ideal adsorbent material with low cost, highdensity, large specific surface area, and porous structure. In addition, it containstitanium and iron which have good adsorption properties. There are many reportsabout the adsorption properties of steel slag and modified steel slag for removal ofphosphate, ammonia nitrogen and lead. However, using modified steel slag to remedyheavy metals pollution in marine has not been reported in China. Therefore, this studyuse steel slag as experimental material and prepared the modified steel slag in in fourways, through modifying acid, alkali, salt and heat. Effects of contact time, initialconcentration, temperature and pH on adsorption of mercury and arsenic wereinvestigated. The the security of steel slag was analysed. These results indicated that:(1) When the contact time is120min, temperature is15-35℃and in weaklyacidic conditions,5kinds of slag will remove mercury effectly. The removal of steelslag is no significant difference in the pH between6and8. The change of initialconcentration has diffenert effects on different steel slags. Alkali, hot and acidmodified steel slags can adapt to the changes in the concentration of mercury inseawater. Mercury removal is improved by using the modified steel slag and theremoval of acid and alkali modification is better than others. Maximum removals ofmercury and arsenic are95.9%and91.9%. Under the same conditions, they areimproved compared with unmodified slag. The adsorption of mercury by5kinds ofsteel slag follows the Freundlich isotherm model，and the correlation coefficient isabove0.9except acid modified steel slag. (2) When the contact time is120min, temperature is15-35℃and in weaklyacidic conditions,5kinds of slag will remove mercury effectly. But the removal ofmodified steel slag is no significant difference in the pH between6and8. The changeof initial concentration has diffenert effects on different steel slags, and alkalimodified steel slag can adapt to changes in the concentration of arsenic in seawater.Mercury removal is improved by using the modified steel slag and the removal ofalkali and heat modification is better than others. Maximum removals of mercury andarsenic are90.9%and85.1%. Under the same conditions, they are improvedcompared with unmodified slag. The adsorption of arsenic by unmodified and acidmodified steel slags follows the Langmuir isotherm model，and the correlationcoefficient is above0.9, the adsorption of arsenic by alkali, salt and heat modifiedsteel slags follows the Freundlich isotherm model，and the correlation coefficient isabove0.9except heat modified steel slag.(3) It is security of using alkali alkali modified steel slag to remedy heavy metalspollution in marine. Steel slag will increase the inorganic nitrogen and activephosphate concentration, but they can meet the2nd seawater quality standards;decrease the concentration of heavy metals such as mercury, arsenic, copper, lead,zinc and cadmium, and meet1st class seawater quality standard; impact the pH, buttaking into account the ocean is a huge, open buffer system and put in the appropriateamount of slag does not have a greater impact of pH.In summary, using modified steel slag to remedy heavy metals pollution inmarine can not only slove the problem of mercury and arsenic pollution in marine, butalso achieve “waste by waste” and solve the problem of slag accumulation. It willconducive to the sustainable development of steel industry and have broad applicationprospects.