Research On The Adsorption Of Dyes And Phenolic Pollutants From Aqueous Solution Employing Activated Carbon Based On Salix Psammophila

Organic phenol compounds and anionic dyes are typically teratogenic,carcinogenic, mutagenic pollutants, which are used in a wide range of application,such as pharmacy, mining, metallurgy and dyes preparation. Activated carbon was regarded as one of the superior adsorption materials due to its huge specific surface area and well-developed pore structure. Salix psammophila is generalized to plant in the Ordos of Inner Mongolia, and rejuvenates every 3-5 years. The branches are processed to Salix Psammophila, but the scraps are wasted seriously. In this paper,according to one step of pyrolysis and activation, Activated Carbon based on Salix Psammophila(SPAC) is prepared through activating Salix Psammophila(NSP)employing NH4H2PO4 as activator, and then SPAC is employed as adsorbent for removal of organic phenol(2,4-dichlorophenol(2,4-DCP), catechol(CA) and p-nitrophenol(p-NP)) and anionic dye(Alizarin Red(AR)) from aqueous solution in hope of making waste profitable.Firstly, the best condition of preparation activated carbon was discussed,including the factors of NH4H2PO4 concentration, activation time, activation temperature and activation agent impregnated time. The SPAC was characterized by Fourier transform infrared spectrum(FT-IR), Scanning electron microscope(SEM),X-ray diffraction(XRD) and Boehm titration. It is found that SPAC possesses high specific surface area, abundant mesoporous structure and functional groups(e.g.-OH、-NH2).Secondly, the influence factors of adsorption behaviors of 2,4-DCP, CA, p-NP and anionic dye AR on SPAC, such as contact time, dosage of adsorbent, pH value,initial concentration, temperature, and then the optimized adsorption conditions were selected. Whereafter, the experiment data was analyzed by isothermal equations and dynamic models. In addition, the competitive adsorption behavior of the binary systems of AR, 2,4-DCP and AR, p-NP as well as three component system of2,4-DCP, p-NP and AR were also investigated. The main details were summaried asfollows:(1) According to the adsorption performance of 2,4-DCP, CA, and p-NP by SPAC in single component system, it is observed that pH play an important role on adsorption and the optimum adsorption pH were 5.5, 4.5 and 4.5 for 2,4-DCP, CA,and p-NP, respectively. The saturated adsorption capacity of 2,4-DCP, CA and p-NP were 1.775, 1.028 and 1.858 mmol g-1 at 298 K, respectively. The adsorption equilibrium data of adsorption of 2,4-DCP, CA and p-NP followed Freundlich,Temkin and Koble-Corrigan isotherm models. Moreover, the adsorption processes were fitted well with the Pseudo-second-order and Elovich kinetic equation. The adsorption procedures were governed by chemical adsorption and ion exchange.The study on the adsorption properties of AR elucidated that the adsorption capacity takes on the trendy of increasing firstly, reaching the maximum value at pH4.5 and then declining when the pH exceeds 4.5. At 298 K, the adsorption capacity on AR at an equilibrium concentration was 0.171 mmol g-1. Isothermal nonlinear fitting analysis and adsorption kinetic results demonstrated that the adsorption process were the same with the process of CA.Intraparticle diffusion demonstrated the adsorption of the four kinds of materials utilizing SPAC was dominated jointly.(2) The adsorption studies of 2,4-DCP and AR or p-NP and AR in binary system on SAPC showed that the total adsorption capacity of SPAC for 2,4-DCP and AR(p-NP and AR) in binary system was higher than that of AR, while less than 2,4-DCP(p-NP) in single system. The competitive adsorption of bi-component system follwed in the order : 2,4-DCP > AR and p-NP > AR, respectively. The pseudo-second-order and Elovich model were better to explain the dynamic adsorption behaviour in binary system.Comparison of adsorption characteristics among 2,4-DCP, p-NP and AR in ternary system reveals that the competitive adsorption obey the order: 2,4-DCP >p-NP > AR. The kinetic adsorption process can be described by pseudo-first-order for the adsorption of AR, mainly depending on physical adsorption, and by pseudo-second-order for the adsorption of 2,4-DCP and p-NP, relying on chemical adsorption.(3) The results of desorption and regeneration experiments confirmed that the function of NaOH solution(0.1 mol L-1) was obviously superior to that of distilled water, absolute alcohol, NaOH solution(0.05 mol L-1). After three cycles operations,the regeneration rates were 73.6%, 68.9%, 81.5% and 66.5% for 2,4-DCP, CA, p-NP,AR, respectively.