| China is the largest coke producing and exporting country in the whole world, whichproduced over200million tons of coking wastewater per year. Coking wastewater containmany toxic and refractory organic pollutants, which may not only prolong the hydraulicretention time (HRT), some persistent pollutants may through volatilization and sludgeadsorption into the natural environment tailwater caused more serious ecological risk, mayalso be discharged into the natural water due to their low concentration. Due to the adsorptioncan quick cut the effluent toxicity and the process is flexible and convenient, adsorption as apretreatment technology can quickly regulate wastewater quality structure, improve thebiodegradability of coking wastewater, reducing the difficulty of biological wastewatertreatment.Vermiculite is a kind of natural clay minerals, has obvious cost advantages as adsorbent.For solving the defaults of natural vermiculite and intercalated organoclay such as low surfacearea and inhomogeneous organic loading, natural vermiculite was activated by acid leachingand was then modified by trimethylchlorosilane (CTMS) and triethylchlorosilane (CTES).The modified materials were characterized by FTIR, BET, SEM and TG, and its adsorptionproperties were investigated. Main results as follows:(1) Diethyl phthalate (DEP), a typical hydrophobic micro-organic pollutant, was used totest the adsorption capacity of different adsorbents. The adsorption amounts of DEP were63.7,51.2and15.7mg·g-1for CTES, CTMS and intercalated organovermiculite in this study,respectively. The high organic affinity of modified acid vermiculite was due to both the biggersurface area and homogeneous organic loading. The isotherms exhibited linear characteristicsand could be described by Henry and Freundlich equations, indicating that partition process isthe main control mechanism of DEP’s removal.(2) The hydrophobicity of the organic compounds, characterized as octanol-waterpartition coefficient (logKow), was the crucial factor for the hydrophobic adsorption. Becauseof lager logKowthan DEP, dibutyl phthalate (DBP) was used to test the adsorption capacity ofdifferent adsorbents. Experimental results indicated that the adsorption capacity of DBP byCTES-V is about50times of DEP. The hydrophobicity of the organic matter is an importantfactor affecting the adsorption capacity of the adsorbent.(3) Organic modified acid-vermiculite has targeted hydrophobic adsorption function inthe phenol and DEP mixed solution comparison with powder activated carbon, nonionic resinand organic intercalated vermiculite. As a hydrophobic adsorbent, the organic modified acid-vermiculite is able to adsorb the hydrophobic organic compounds, provided anexperimental basis for the pretreatment of coking wastewater.(4) Adsorption the organic components of coking wastewater with five kinds ofadsorbent. The TOC removal of coking wastewater by the powdered activated carbon,non-ionic resin, organic intercalated organovermiculite, CTMS-V and CTES-V is24.5,11.3,2.88,4.4and6.96%, suggesting that adsorption should not be the directly method to dealwith the raw coking wastewater. However, anaerobic biodegradation experiments show thatthe effluent after adsorbed has higher degradation than the raw wastewater, the wastewaterafter CTMS-V adsorbed has the highest degree of degradation, which the TOC degradationrate reached40%.Three-dimensional fluorescence spectroscopy and GC/MS analysis showedthat the organic modified acid-vermiculite adsorbed the refractory organics, such as pyridine,nitriles, polycyclic aromatic hydrocarbons,10types of more than50kinds of refractoryorganic matter. With respect to powered activated carbon, non-ionic resin and organicintercalated organovermiculite, the organic modified acid-vermiculite reduce the toxicity andmicrobial inhibition of raw coking wastewater, the B/C ratio increased from0.293to0.420and0.496, the toxic refractory industrial wastewater is shift into the general industrialwastewater, its better to be used for actual wastewater pretreatment method. |
PDF Full Text Request