| In this paper, the dry sludge adsorbent, acidic sludge absorbent and alkali sludge adsorbent respectively were produced by the digestion sludge which produced from sewage treatment plant ,through the dry treatment, pickling and caustic washing treatment. Structure of sludge absorbents was characterized by nitrogen adsorption isotherm and infrared spectroscopy (IR). the thermal stability was mensurated by differential thermal analysis apparatus. The results show that three kinds of sludge absorbents have abundant medium-pores and some big-pores and some tiny-pores.The calculated results of BET adsorption model indicate that the specific surface area of alkali sludge adsorbent is bigger than that of dry sludge adsorbent and acidic sludge absorbent. The results from DSC indicate that three sludge absorbents have thermal stability.Through to dry sludge adsorbent, acidic sludge adsorbent and alkali sludge adsorbent to the methylene blue, the gentian violet and malachite green's adsorption performance study, discovered that three kinds of sludge adsorbent have the obvious adsorption effect to three dyes, the elimination rate is above 85%.The dye initial concentration, the adsorption time, the adsorption temperature, the pH value and the salinity to adsorb have certain influence. Three kind of sludge adsorbents are long to the methylene blue adsorption time comparison, about 14h. The adsorption time of alkali sludge adsorbent to malachite green is shortest in the experiment and about 2h may achieve the adsorption equilibrium. Regarding the pH value's influence, pH value is advantageous in neutrality and under the alkalescent environment to the sludge to the dye adsorption. The existence of salt has certain inhibitory effect to adsorption process.The adsorption process all fit the Langmuir and the Freundlich isotherm model excellently. The increase of temperature does not favor the adsorption process, when the temperature is 298K, the maximum adsorption capacities of dry sludge adsorbent, acidic sludge absorbent and alkali sludge adsorbent to the methylene blue respectively are 88.50 mg·g-1, 53.19 mg·g-1, 114.9 mg·g-1. the maximum adsorption capacities of dry sludge adsorbent, acidic sludge absorbent and alkali sludge adsorbent to the gentian violet respectively are 62.89mg·g-1, 57.80 mg·g-1, 142.9 mg·g-1. the maximum adsorption capacities of dry sludge adsorbent, acidic sludge absorbent and alkali sludge adsorbent to the malachite green are 149.3mg·g-1,57.14 mg·g-1,151.5 mg·g-1 ,respectively.According to the influence of the temperature to the adsorption, the change of apparent Gibbs free energy, the enthalpy as well as the entropy of three kinds of sludge adsorbents to three dye are calculated, The result indicated that the adsorption processes are spontaneous ,exothermic and entropy reduced process. The influence of adsorption time to the adsorption shows that the adsorption process conforms to the second-order model. The digested sludge as a inexpensive absorbent may disposal the printing waste water effectively. |
PDF Full Text Request