Studies On The Competitive Adsorption Of Pb, Cd And Cu To Solid Matters In Multi-solid Coexisting Natural Aquatic System

Solid materials in natural water environments exist in the patterns of surface coatings, suspended particulate materials and deposited sediment, which compose the complex coexistence system with water that conducts heavy metals pollution. However, heavy metals pollutants in water coexist as well, and the really single metals assimilation is rare, yet the absorption between heavy metals are frequent. Before, the research on the coexistence of the variety of heavy metals pollutants and solid materials are rare. This research simulates the coexistence system of variety of solid materials in natural water environment and thermodynamics of variety of solid materials'absorption to heavy metals, which could reflect the reality of water environment better.The research selects water in Songhua River the representative sample and take advantages of selective SC, DC, and SPA samples, in the simulation of specific conditions, Study of the adsorption thermodynamic characteristics of Pb,Cd and Cu in single solid material system, including the situation of each stand alone,two of them exist and all exist; and the same stduies in multiple solid material coexistence system.Besides, for the same solid-phase material,compare the two systems in the competitive adsorption of metal,and study the metal selectivity of solid material. This research is mainly on the analysis of thermodynamics of Pb, Cd,Cu in natural water with Langmuir adsorption isotherm, and therefore distribution coefficient would be used to represent absorption capacity of solid materials to heavy metals and nonlinear least squares fitting would also be used to analyze different absorption data to confirm absorption parameters.Following conclusions were drawn,1.It presents competitive between metals. When two or three of three metals coexist, it would present that the metal that have stronger absorption capability would reach the absorption point earlier than others, to influence the absorption to other metals. For surface coatings, suspended particulate materials and deposited sediment, coexistence of metals makes the volume lower and the metals would make the competition as they struggle to reach the absorption point against each other. At the beginning, the volume of metals absorption would not be affected much and the competition does not strongly present as the metal ions'density is low, the competition capacity is weak and the absorption accommodation is not fully occupied. Coexistence of three metals presents the least absorption volume and the competition is the most obvious.2.There are similarities and differences between the metals absorptions in two systems. For surface coatings, suspended particulate materials and deposited sediment, no matter in single or Varity of solid materials system, to the same system, when metals coexist, the absorption capacity of each metal would be lower. To add to outside metal ions, they struggle for the absorption point that makes the absorption volume of each metal influenced by different senses.3.For Cd and Cu, the absorption volume is lower in multiple solid materials system than when they are in single system. Competition in the variety of solid materials makes the absorption volume reduced and the absorption capacity influenced. But for Pb, it presents the opposite. In some sense, in the system of the coexistence of variety of solid materials, the original absorption advantage that the deposits have is replaced by surface coatings, suspended particulate materials. When surface coatings, suspended particulate materials and deposited sediment coexist, they would be able to get more Pb in competitive absorption.4.The choice for metals is Pb, Cu and Cd. In single and variety system, the absorption order and choice are the same with when they exist independently when surface coatings, suspended particulate materials and deposited sediment coexist. When the metal density is higher than 0.25μmol/L, the absorption volume of Pb would be lower than Cu. The absorption choice to heavy metals for solid materials, which perhaps is related to the composition and the nature of surface coatings, suspended particulate materials and deposited sediment and their components, their forms. Besides, perhaps they are related to the nature of metals'physics and chemicals, such as first-level hydrolysis constant, nic radius, ectronegativity.5.Distribution coefficient presents similar regularity, and the order is Pb>Cu>Cd. The distribution situation is the same in single metal system from in variety of metals. When metals exist independently, the distribution order is Pb>Cu>Cd, the same with the absorption capacity and choice order. The distribution coefficient reduces a lot when the medals coexist than they exist independently, which means the competitive absorption happens between them when they coexist and the distribution has inverse relationship with the original density. When varieties of metals coexist is equal to increase the total density and the influence between each other, the competition to struggle for the absorption potential, induced the distribution coefficient. No matter in single system or in variety system, it is almost the same about the absorption order and choice when metals coexist. This implies the coexistence of metals does not change the absorption system but induces the absorption capacity.