Preparation Of Clay-based Ceramics And Its Adsorption Behaviors For Cu²⁺ And Zn²⁺

Adsorption is widely applied in wastewater treatment because of its advantages of easy operation, convenient use and effective processing. Therefore, the exploitation of new adsorption materials with low cost, strong regeneration and non-secondary pollution has become the research focus in the filed of environmental material.In order to treat heavy metal wastewater, this research used clay as the main material, vermiculite as the modifier, pulverized coal and/or graphite as the single or composite pore-forming agent to prepare clay-based ceramsite adsorbent. The affects of the variety, particle size, and quantity of the additives and particle proportion on the apparent porosity, volume density and pore structure were investigated. With the increase of the particle size of pulverized coal, graphite and vermiculite, the apparent porosity of porous ceramics first increased and then decreased, and the volume density showed the opposite trend. While the particle size of coal, graphite and vermiculite was 60-80,60-80 and 100-120 meshes respectively, the best quality of porous ceramics was achieved. With the increase of the particle size of the pulverized coal, the microscopic pore structure of porous ceramics changed from 3D transfixion type to closed micropore type, the porosity reduced and the pore volume increased. Compared with the single pore-forming agent, the composite pore-forming agent increased the apparent porosity and decreased the volume density. When pulverized coal (15%) and graphite (5%) were used as composite pore-forming agent, the apparent porosity was 45.49%, the volume density reached 1.296g/cm3. Under this condition, the apparent porosity was 58%, the volume density reached 1.081g/cm3 as the amount of vermiculite was 2%.With Cu2+and Zn2+solution as model wastewater, the adsorption performance and influencing factors of the clay-based ceramsite were investigated. The adsorption of the ceramsite was directly influenced by the quality of the adsorbent, the solution pH value, the metal ions'initial concentration and interfering cations'variety and quantity.The experimental data was analyzed on the basis of adsorption principles to reveal the porous ceramics'adsorption mechanism and dynamic rules on heavy metal wastewater. The analysis showed that the porous ceramics' adsorption to metal wastewater included three stages:the initial fast adsorption, the slow adsorption, and the equilibrium adsorption. The Cu2+adsorption process was in line with Langmuir equation and Freundlich equation, while the Zn2+adsorption dynamics well abided by the Quasi-two adsorption rate equation and Intragranular transport model. This result indicates that the adsorption rate was mainly controlled by chemical adsorption and more adsorption stages were involved. The EDS and XRD analysis show that copper and zinc was adsorbed to the surface of the ceramsite in the forms of Cu2O and ZnO.