The Adsorption Of Environmental Pollutants By Active Carbon Prepared From Waste Crop And Bentonite

performance and cost of adsorbent are the important parameters in adsorption process. The preparation of cheap and efficient adsorbents has been a active area in environment treatment. There are a huge amount of by-products in agricultural production, such as straw. At present, these low value resources are used as fuel or are wasted. The utilization of agricultural wastes is very low. Making better utilization of the agricultural wastes is significant to save resources and increase the agricultural value. In this thesis, active carbon which was prepared by waste crops.The removal of environmental pollutants by active carbon and bentonite was investigated. The spectrometric data in adsorption processes were analyzed by chemomatric methods. The adsorption behavior in mixed solute systems and regeneration of adsorbents were investigated.1. The adsorption of dye and phenol by active carbon under different adsorption approachesActivated carbons produced from corn stalks (CSAC) via H3PO4 activation and microwave irradiation. The removal of Reactive Brilliant Red K-2BP (K-2BP) and phenol by adsorption from single and binary mixture solutes were tested. The adsorption isotherm data were analyzed by Langmuir, Freundlich, and Redlich- Peterson models. The adsorption capacities of K-2BP and phenol on CSAC are 126 and 112 mg/g, respectively. The adsorption equilibrium constants are 34.8 and 8.07 L/g for K-2BP and phenol, respectively. The adsorption kinetics was fitted by the pseudo-first-order and pseudo-second-order kinetic models. Three adsorption approaches, including two-step adsorption, sequential addition of adsorbent, and the combination of loaded and fresh adsorbent, were tested and comparaed. Compared to one step adsorption, the removal efficiency and the time efficiency in the three approaches are improved. The loaded CSAC was regenerated by microwave radiation. The results show that CSAC is an efficient adsorbent for wastewater treatment. 2. The adsorption of single-dye and mixed-dye solutions in columns of activecarbonActivated carbons produced from pods (PAC) via H3PO4 activation and microwave irradiation. The adsorption isotherms and kinetics of Acid Scarlet GR (AS-GR), Weak Acid Orange (GS), Indigo Carmine (IC), and Reactive Violet (K-3R) on PAC were measured. It was shown that the isotherms of the four dyes follow Langmuir model. The saturation amounts of AS-GR, GS, IC, and K-3R adsorbed are 436, 327, 249 and 175μmol/g, respectively. The adsorption equilibrium constants of AS-GR, GS, IC and K-3R are 0.732, 0.243, 0.529 and 0.0593 L/μmol, respectively. The adsorption kineticses are well fitted by a pseudo-second-order kinetic models. The adsorption behavior in fixed-bed adsorber of the four dyes from single and mixted dye solutions were investigated. In adsorption from mixed dye solution, difference in the breakthrough curves for each dye was observed. The influence of initial dye concentration, liquid flow rate, and carbon bed depth on the breakthrough volume were tested. In a small scale adsorption column, the adsorption efficiency and rate are less than those in one step batch adsorption.3. Data analysis in adsorption of methylene blue on bentonite and regeneration treatmentBentonite wass employed to remove methylene blue (MB), which is a commonly-used model cationic dye in simulated dye wastewater. In the determination of the concentration of MB by a spectrophotometric method, the linearity of the calibration curve is not good enough. It was shown that the absorptive spectrum of MB solution is influenced by its concentration, which results in a large systematic error in the determination of the concentraton of MB. The aggregation behavior of MB is investigated by spectrometric method. An iterative arithmetic was proposed to obtain the aggregation equilibrium costant of MB and the absorptive spectrum of monomer and dimmer of MB. The influence of the aggregation equilibrium on the estimation of MB is eliminated. The regeneration and reuse of the loaded bentonite were tested. It was shown that adsorption capacity of the calcined bentonite is much less that that of the fresh bentonite. The bentonite/carbon prepared by microwave method adsorbs cationic and anionic dyes effectively. 4. Piezoelectric quartz crystal microbalance monitor adsorption properties of acid dyes in the surface of chitosan.The response characteristic of the third and fifth harmonic models in apiezoelectric quartz crystal (PQC) were investigated by an impedance analysis method.On this basis, adsorption properties of acid dyes in chitosan film was monitored by PQC. It was shown that for the same change of mass ladingthe, the ratio of frequency change in fundamental frequency, third and fifth harmonic models is 1:3:5. Harmonic frequency reduce linearly with increasing( )ρη1/2,while the resistance increase linearly. Under the experimental conditions, the ratio of the frequency change and the resistance change in the fundamental frequency, third and frith harmonic models are 1:1.68:1.96 and 1:1.85:2.01 respectively. This proportional relationship is not only inconsistent with the ratio of harmonic times, but also inconstant with the ratio of the frequency in piezoelectric theory. Compared to the fundamental model, The longitudinal wave effect is weak in the harmonic models. The intensity of the longitudinal wave in the harmonic models is about 5% of that in the fundamental frequency model.This is beneficial for improving the stability of QCM.