| Humans have suffered a lot from rapid increase of using organic dyestuffs and heavy metals in industrial processes. Thus, the removal of organic dyestuffs and heavy metal ions from contaminated water is a urgent task. Among the techniques used in removaling organic dyestuffs and heavy metal ions, adsorption method is more reliable for its advantages such as high efficiency, easy operation, variety of adsorption materials, low cost and so on. In this paper, the thermo-sensitive adsorbent of calcium alginate/methyl cellulose beads?CAMCBs? were prepared. CAMCBs have good adsorption capacity of methylene blue?MB? and Ni??? at low temperature, good desorption capacity at:-high temperature, and also can be easily recycled.The preparation conditions, the properties of adsorption and desorption were investigated. Experimental results showed that with the preparing CAMCBs conditions of mMc:mSA of 0.1:0.1?g:g?, calcification solution at calcium chloride mass concentration of 5%, the agitation speed of 200 r·min-1, the calcification time of 240 min, solution temperature of 30?,CAMCBs had the integrated optimal properties of thermo-sensitive adsorption and strength. CAMCBs pepared in this condition had the biggest difference of 57.5% for MB removal rates at 30? and 60?,and the intensity of 2.12 N. By using 1% mass concentration of calcium chloride, or calcium lactate, or calcium acetate as desorption solvent, the MB desorption rates for CAMCBs after MB saturated adsorption were 90.5%,87.8% and 83.8%, respectively. The MB desorption equilibrium times of CAMCBs at 30? and 60? using calcium chloride as desorbing agent were 15 min, while using calcium lactate or calcium acetate as desorbing agent which were 30 min and 15 min, respectively. The MB adsorption capacities of CAMCBs with calcium chloride as desorbing agent in first time and fifth time were 73.7 and 73.1 mg·g-1, respectively. The difference of both MB adsorption capacities was only 0.6 mg·g-1. While Calcium lactate or calcium acetate was used as desorbing agent, the difference of both MB adsorption capacities was 2.3 and 5.3 mg·g-1, respectively. These results showed the CAMCBs had good reusable property. With the CAMCBs dosage of 2 g·L-1 and Ni??? mass concentration of 30 mg·L-1, the Ni??? removal rate of CAMCBs at 30? was 65.9%, and the adsorption equilibrium time was 45 min. The Ni??? equilibrium adsorption capacity of CAMCBs decreased with the increase of temperature. The best pH for CAMCBs adsorption Ni??? was 8, and the adsorption capacity increases with the increase of initial concentration.The adsorption behaviours of Ni??? on CAMCBs were analyzed by the following three kinds of dynamic models:the pseudo-first-order kinetics, the pseudo-second-order kinetics, Bangham equation, and four kinds of isothermal adsorption models:Langmuir equation, Freundlich equation, Temkin equation, D-R equation, and thermodynamic equation. The adsorption property of Ni??? on CAMCBs obeys pseudo-second-order kinetics equation and Langmuir equation. According to negative values of ?H and ?S, the adsorption is an exothermic process of entropy reduction. Rising temperature is not conducive to the adsorption. |
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