Effect Of Additives On Heavy Metals Adsorption On Sediments In Inner Mongolia Section Of The Yellow River

Surficial sediments are one of the most important components in the watersystem. Surficial sediments are the source and the sink of heavy metals inwater. Adsorption is one of the most important reactions of heavy metalsamong the series of migration and transformation of heavy metals onsediment-water interface. Hydrous metal oxides and organic matters whichare the content of surficial sediments would affect the absorption of heavymetals. The heavy metals absorbed on sediment would desorb with the tinychanges of environment around. Hence it is necessary to investigate theremediation of heavy metals in contaminative sediments. The Yellow Riversection of Inner Mongolia is a typical and representative section for studyingthe heavy metal pollution of the Yellow River. There are lots of pollutants,which have heavy industrial wastewater, production wastewater, agriculturaland domestic wastewater discharged into the Yellow River, resulting indifferent degrees of pollution of the Yellow River in Inner Mongolia is boundto affect masses’ health.In this research organic matters （humic acid and tannin）, Fe oxides（ferrihydrite and goethite） were added respectively as additives to surficialsediments. Considering that the additives may affect the physiochemicalproperty of surficial sediments, the components of surficial sediments（organic matters and Fe oxides） were selected in this study. This researchcompared the effect of additives on the adsorption of Cd²⁺, Cu²⁺and Pb²⁺ontosurficial sediments. The influencing factor of adsorption time, various initialconcentrations, temperature, pH and diameter of particulates sediments toadsorption of Cd²⁺, Cu²⁺and Pb²⁺were discussed. The adsorption isothermsand adsorption kinetics were fitted and distribution coefficients werecalculated. The results illustrated that:（1） According to the the Yellow River sediments in the whole rock analysisand clay mineral composition analysis of the mineral composition ofsediments in Inner Mongolia section of the Yellow River. Organic matter in sediment on heavy metal adsorption process has a certain intermediatebridging effect. The effect of organic additives on the adsorption quantity ofCd²⁺, Cu²⁺and Pb²⁺onto surficial sediments is different with each other.Compare to tannin, the humic acid increase adsorbance more easily. Theorganic additives dissolution may be one of the reasons that affect theadsorption quantity of heavy metals. Adsorption of Cd²⁺, Cu²⁺and Pb²⁺ontosediments increases after the addition of ferrihydrite or goethite. Themechanism of heavy metals absorbed onto Fe oxides additives may be theeffect of ligand exchange shown in quoted passage. Fe oxides would all moreor less increase the adsorption of Cd²⁺, Cu²⁺and Pb²⁺onto sediments.（2） In a certain period of time, Cd²⁺, Cu²⁺and Pb²⁺adsorption capacity andsurface sediments with contact time extending linearly, at1h after sedimenton heavy metal adsorption curve flattened,2h after reaching the adsorptionequilibrium. After2h in sediments on Cd²⁺, Cu²⁺, Pb²⁺maximum adsorptionquantities of respectively98.3%,99.2%and97.8%, and the effects ofadditives on humic acid and ferrihydrite after sediment on heavy metaladsorption quantity increases significantly, doped with tannic acid effect isrelatively poor. Adsorption of heavy metal sediment as the reaction process isin accordance with Elovich equation（R²>0.93）, but the doped additivereaction with double constant rate equation of dynamics. Different additiveshave different effect on adsorption anddesorption of different heavy metals.The order of difficulty about heavy metals’ fixing is: Pb²⁺> Cu²⁺> Cd²⁺.（3） The results illustrated that the adsorption processes of sediments withdifferent proportions of surficial sediments main constituents to Cd²⁺, Cu²⁺and Pb²⁺were consistent with Langmuir adsorption isotherm curves（R²≧0.95,p≦0.01, n=7）. Doping of humic acid, tannic acid, ferrihydrite after surfacesediments of Cd²⁺, Cu²⁺and Pb²⁺maximum adsorption capacity were higherthan those of sediments as tannic acid is inhibited, and the doped on surfacesediments of Cd²⁺, Cu²⁺and Pb²⁺absorption.（4） Sediments of main chemical constituents in iron oxides and organicmatter on Cd²⁺, Cu²⁺, Pb²⁺adsorption contribution exists difference, the distribution coefficient of3kinds of heavy metals in the solid–liquid and ithas made a detailed description of distribution. Effects of additives with aheavy metal sorption capability influence order: humic acid> ferrihydrite>goethite> tannic acid. Under the30℃system of Cd adsorption on sedimentsis higher than the overall system at25℃and18℃, indicating that theadsorption reaction is endothermic. Experiment in the control of solution pHin5⁷between, removing both H+on the adsorption were investigated, alsoexcludes the Cd²⁺, Cu²⁺, Pb²⁺sedimentation. Cd²⁺, Cu²⁺and Pb²⁺adsorptioncapacities of sediments with additives increased with the decrease of diameterof suspended particulates in water. The operating process of the experimentselected150mm sediments.