| This paper mainly focuses on utilization of agricultural and forestry waste corn cob and furfural-residue. Through their chemical modification, adsorption performances of the modified adsorbents were examined in detail by treatment wastewater containing dyes or phenols pollutants. Various factors including dosage of adsorbent, solution pH, adsorption time, initial solution concentration, temperature etc, were studied. The adsorption thermodynamics and dynamics were applied to analysis the process mechanism. The results are as follows:1. After the corn cob was modified by phosphoric acid, the equilibrium adsorption of methylene blue and rhodamine B in water on modified adsorbent was much higher than that of the unmodified raw one. For adsorption of methylene blue by adsorbent from modified corn cobs, the best condition was: the equilibrium adsorption quantity of methylene blue reached 99.06 mg/g in 60 min with 6.0 pH, 0.05 g as dosage, 100 mg/L methylene blue concentration and 25 ℃ temperature. For adsorption of rhodamine B, the best condition was: the equilibrium adsorption quantity of rhodamine B reached 33.12 mg/g in 140 min with 2.0 pH, 0.15 g as dosage, 100 mg/L rhodamine B concentration and 25 ℃ temperature. The removal rate of both cases can achieve more than 99%. The kinetics in adsorption process was fitted by pseudo first-order kinetics equation, pseudo second-order kinetics equation and Elovich equation. The results showed that the adsorption process was carried out quickly, pseudo second-order kinetics equation could fit the adsorption process better and the adsorption mechanism was stoichiometric displacement mechanism. The adsorption equilibrium isotherm was fitted by Langmuir and Freundlich isothermal adsorption equations. The study investigated the impact of temperature on adsorption equilibrium and analyzed the thermodynamics of adsorption. It showed that Langmuir equation was more suitable for specifying adsorption equilibrium; the rising of temperature was propitious to adsorption; both ?H0 and ?S0 in adsorption process were positive and entropy(?S0) was the driver of adsorption process.2. Industrial solid waste from furfural production was chemically modified, and the adsorption characteristics of the modified adsorbent on phenol and p-nitrophenol in water were also investigated. The results showed that the adsorption performance of furfural-residue which was activated by ZnCl2 at 600 ℃ on phenol and p-nitrophenol in water solution was the best. For adsorption of phenol solution, the best condition was: the equilibrium adsorption quantity of phenol reached 18.55 mg/g in 120 min with 6.0 pH, 0.2 g as dosage, 150 mg/L phenol concentration and 25 ℃ temperature. For adsorption of p-nitrophenol solution, the best condition was: the equilibrium adsorption quantity of p-nitrophenol reached 49.36 mg/g in 60 min with 4.0 pH, 0.1 g as dosage, 200 mg/L p-nitrophenol concentration and 25 ℃ temperature. The removal rate in the best condition could achieve more than 98%. For the same experimental conditions, the adsorption quantity and removal rate on phenol and p-nitrophenol by modified adsorbent was higher than the unmodified adsorbent. The adsorption kinetics was fitted by pseudo first-order kinetics equation, pseudo second-order kinetics equation. The results showed that the adsorption process was in line with pseudo second-order kinetics equation and the process was fast. The adsorption isotherm was fitted by Langmuir and Freundlich equations, it was shown that the Langmuir equation was much better, and the adsorption quantity decreased along with the rising of temperature. The exothermic process was spontaneous physical adsorption.3. By comparison of infrared spectrum, electron microscope scanning, thermogravimetric(tg), XRD diffraction analysis and BET characterization between unmodified and modified adsorbent from furfural-residue, we can see that the pore structure in the surface of adsorbent which was activated by ZnCl2 arranged quite in order and this adsorbent also contains O-H, C-O-C,-C(O)-O-C and other functional groups. Though the adsorbent activated by H3PO4 contains the surface gene of adsorbent activated from by ZnCl2, there is also the structure of aromatic ring or alcohol ketone(carbonyl and phenolic hydroxyl). The surface of all the modified adsorbents contains lots of quai-graphite crystallite, and the specific surface area enlarges significantly as well. |
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