Preparation Of Modified K-feldspar And Its Adsorption On Heavy Metal Ni(Ⅱ) In Waste Water And Soil

Under the concept of clean,circular economy and economical society,the development of environmentally-friendly,low-cost,high-recovery environmental mineral materials is the current mainstream trend.K-feldspar is a kind of natural aluminosilicate with abundant and wide distribution.It has special pores or channels and some ion exchange properties,which makes it have some potential in the field of treatment environmental pollution.However,because of its poor adsorption properties and stable properties,K-feldspar can not be directly used in the treatment of waste water or soil that polluted by heavy metals.Unless,disadvantages of K-feldspar were conquered by modifications.In this paper,two kinds of K-feldspar adsorbents materials were prepared by the modification of K-feldspar high-temperature calcining and surface-loaded hydroxyapatite（HAP）.They were respectively used for adsorption of Ni²⁺in waste water and soil.The main contents are as follows:1.Preparation and Characterization of Modified K-feldsparUnder the condition of high temperature,K-feldspar is calcined by mixed with Calcium compound additive,and the single-factor experiment and orthogonal experiment are used to determine the optimal scheme for the preparation of the adsorption material（Ca-K）.The preparation conditions are as follows:K-feldspar mass of 1g,CaSO₄ mass of 0.08g,CaCO₃ mass of 0.3g,calcining temperature of900℃,calcining time of 3h.;Under this preparation condition,the adsorption rate of0.5g Ca-K to 10mL Ni²⁺solution with pH of 4 and initial concentration of 200mg·L^-1could reached 96.70%.K-feldspar was chosed as material to produce hydroxyapatite/K-feldspar composite absorbing materials（HAP-K）via liquid phase synthesis,The optimum modification conditions of the HAP-K adsorption materials are also determined:m（K-feldspar:HAP）of 0.4,stirring temperature of 25℃,maturing time of 18h,stirring time of 1.5 hour,Under this experimental condition,the adsorption rate of0.5g HAP-K to 10mL Ni²⁺solution with pH of 6 and initial concentration of 200mg·L^-11 could reached 98.34%.XRD,SEM,and BET instruments are used to characterize the phase,morphology and pore structure of K-feldspar respectively before and after calcined modification by mixed with Calcium compound additive and loaded HAP modification.The results show that the Ca-K modified material present rodlike structure and new phase CaSiO₃.The surface of HAP-K became fine and loose with a larger superficial area and total pore volume apparently after K-feldspar loaded HAP.2.Study on the adsorption of Ni²⁺in waste water by Ca-KAfter the K-feldspar calcined by mixed with Calcium compound additive,the adsorption properties of Ca-K on Ni²⁺is studied.The effects of Ca-K on Ni²⁺adsorption,including Ca-K addition,the initial pH value of the solution,the shaking adsorption time and the initial concentration were discussed.At the same time,this adsorption mechanism was explored in conbining adsorption thermodynamics with adsorption kinetics.The specific performance is as follows:Ca-K addition is obviously effect Ca-K on Ni²⁺adsorption,and the adsorption rate increases rapidly with the increase of Ca-K addition amount,and it tends to be stable when the additive amount is more than 0.2g.When the initial pH of the solution is less than 4,the adsorption of Ca-K modified materials on Ni²⁺is inhibited,but when the initial pH of the solution is higher than 4,it is favorable for the adsorption of Ni²⁺by Ca-K.The whole adsorption process needs 24 hour to reach the equilibrium of adsorption,and the adsorption rate is slow.It is mainly controlled by the intra-particle diffusion and adsorption reaction,which fit the pseudo-first-order kinetic model.The adsorption behavior of Ca-K on Ni²⁺can be adequately described by Langmuir isothermal model.The maximum adsorption capacity of Ca-K is 14.97 mg·g^-1,which was improved about four times over the raw materials.3.Study on the adsorption of Ni²⁺in waste water by HAP-KAfter K-feldspar Loaded with HAP,the adsorption of HAP-K on Ni²⁺in wastewater is studied.The effect of HAP-K on the adsorption of Ni²⁺was discussed.And conbining with adsorption thermodynamics and adsorption kinetics to explore this process.The specific performance is as follows:The adsorption rate of HAP-K to Ni²⁺increases with the increase of HAP-K addition amount,but the unit adsorption capacity of HAP-K modified material decreases with the increase of HAP-K addition amount;The strong acid environment is disadvantageous to the adsorption of HAP-K,and the adsorption of HAP-K is better when the initial pH is 6⁸.Under different Ni²⁺concentrations,the adsorption rate of HAP-K is both fast and slow with the shaking time.The whole adsorption process reach to adsorption equilibrium in 180min and fit the pseudo-second-order kinetic model.The adsorption capacity of HAP-K is up to17.63mg·g^-11 at 25℃,which is 5 times approximately than the raw material.Increasing the reaction temperature is beneficial to enhance the adsorption capacity of HAP-K modified materials,and Langmuir Isothermal model is more suitable for describing this adsorption behavior.4.Study on passivation of Ni²⁺in soil by Ca-K and HAP-KRK,Ca-K and HAP-K are used as passivation agents to investigate the effect of the soil on the adsorption of Ni²⁺and passivation.The results showed that the addition of passivating agent in soil could significantly improve the adsorption and passivation of heavy metals.The modified k-feldspar had better treatment effect than the before modification,especially HAP-K adsorption material.Compared with the original soil,when 5%HAP-K,8%Ca-K or 10%RK is applied to the soil,the soil on the adsorption rate of Ni²⁺were respectively increased by 42.33%,36.90%,and 10.19%,and the passivation effects were respectively improved by 60.23%,54.08%,and23.09%.