Studies Of The Effect Of DOM On The Adsorption Of Cu And OTC In Combined System

By now, many scholars have research efforts on on the effect of dissolvedorganic matter (DOM) on the adsorption behavior of heavy metals or antibiotics. Infact, in the environment, the absolute single pollutant does not exist, in general,various pollutants coexist and form the combined pollution.Hence, we investigatedthe effect of DOM on the adsorption of Cu and oxyteracycline (OTC) in combinedsystem”.This studies included the following aspects:(1) the adsorption of DOM, Cu,OTC on the black soil and the relevant influencing factors (pH, temperature and ionstrength);(2) the DOM effect of the adsorption behavior of Cu and OTC on the blacksoil in the DOM-Cu/DOM-OTC adsorption system, and the interaction between theadsorption and the concentrations, pH and OTC landing sequence;(3) the effect of Cuon the adsorption of OTC and relevant mechanism of the influence of Cu on theadsorption of OTC in the presence of DOM in the DOM-Cu-OTC system.. The mainconclusions are as follows:1. As the time increasing, the adsorption amount of Cu, DOM, OTC firstincreased significantly then tend to reach equilibrium in24h. Proposed second-orderequation can fit the Cu, DOM and OTC adsorption kinetics well. The adsorptionprocess of Cu, DOM, OTC was mainly dominated by chemical adsorption,,andinter-particle diffusion can be one of the main controlling step.2. The adsorption of DOM was affected by pH value, temperature and ionstrength greatly. With pH increasing, the adsorption of DOM tended to be downwardtrend. The increase of the ionic strength can promote the adsorption of the DOM, andthe increase of the temperature can suppress the adsorption of the DOM. Under thedifferent ionic strength and temperature, the DOM adsorption thermodynamics can bewell fitted by Langmuir equation. The adsorption process of DOM on the black soilwas non-spontaneous exothermic entropy reaction, and was enthalpy control process.And the process of DOM adsorption to soil was dominated by chemical adsorption, the main adsorption force was inferred as the bond effect.3. The ionic strength had the same inhibition effect on the adsorption of Cu andOTC to black soil, while the increase of the temperature can promote the adsorptionof Cu and OTC on the black soil. Under different ionic strength and temperature, theadsorption process of Cu and OTC can be well fitted by Freundlich and Langmuirequation. The adsorption of Cu and OTC on black soil was spontaneous endothermicand entropy increase process, and it’s controlled by entropy increase. The enthalpychange showed that this process was mainly dominated by chemical adsorption. Theadsorption forces of Cu in black soil may have hydrogen bonding and dipole bondforce, while the adsorption force of OTC in black soil may have hydrogen bonding.4. In the DOM-Cu combined system, the presences of DOM inhibited theadsorption of Cu on the black soil, and the greater the concentration of DOM, thegreater the inhibition. The DOM significantly reduced Kfvalue, the greater theconcentration of DOM, the smaller the value of Kf. With the increase of pH, theinhibition of Cu adsorption on the black soil by DOM was gradually increased. In theDOM-OTC combined system, the presence of DOM promoted the adsorption of OTCon black soil. When DOM existed, the OTC adsorption process can be well fitted byLangmuir and Freundlich isotherm equation. With the increase of pH value, thepromotion of the adsorption of OTC by DOM was increasing. The order of OTCjoining into the system also influenced the adsorption of OTC, the order of adsorptioncapacity was added simultaneously> added OTC first> added DOM first. Underdifferent order of adding OTC, the OTC adsorption process on black soil can also begood fitted by Langmuir isotherm equation.5. In the OTC-Cu combined system, the presence of OTC inhibited theadsorption of Cu, and the greater the OTC concentration, the stronger the inhibition.The presence of Cu promoted the adsorption of OTC on the black soil, and the greaterthe concentration of Cu, the greater the promote effect. In the presence of OTC, theCu adsorption by soil can be well fitted by Freundlich and Langmuir equation. Withthe pH decreasing, the inhibition of Cu by OTC was increasing. In the presence of Cu, the adsorption process of OTC in the black soil can be well fitted by Langmuirand Freundlich isotherm equation. With the increase of pH, the promotion of OTC byCu enhanced. The order of OTC adding into the system had a significant impact onthe adsorption OTC to black soil, the order of the adsorption capacity was addedsimultaneously> added the OTC first> added the Cu first.6. In the DOM-Cu-OTC combined system, in the presence of Cu, the greater theDOM concentration, the greater the inhibition to OTC, which it was opposite with thatin the binary system, indicating the presence of Cu changed the binding way betweenthe DOM and OTC. When the concentration of the DOM and Cu was certain, with theincrease of pH, the adsorption of OTC to black soil was gradually decreased.