Application Of Zeolite-Activated Carbon Composite Materials To Water Treatment

In this paper, applications of zeolite-activted carbon materials in water treatment, especially in coking wastemwater and heavy metal waste water were studied with static adsorption and enhanced SBR biological mathods. As follows, the detailed contents of Ni2+, Cr3+, COD, ammonia and phenol removal and adsorption properties include the effect of (1) solution pH, (2) initial concentration and (3) adsorption time. Adsorption isotherm modals and adsorption mechanism were also studied discussed. The experimental results are as follows:1.Applications of 4A zeolite-activated carbon composite material on Ni2+ and Cr3+ wastewater with static adsorption method.(1) Solution pH has impact on adsorption of Ni2+ and Cr3+ on composite materials. When the pH is low, too many H+ ions bring adsorption competition and reduce the ion exchange ineraction of Ni2+ and Cr3+. When pH is too high, the precipition of metal ion will block the adsorption. When the pH is 4.2 and 4.3 respectively, and composite materials have the highest adsortption amount.(2) Adsorption capacity increased gradually with adsorption time. Under the same adsorbent dosage and initial concentration, adsorption of Ni2+ needs longer equilibrium time than Cr3+, they are 3h and 2h respectively.(3) With the increase of intial concentration, adsorption amount of Ni2+ and Cr3+ increased, while the removal rate decreased.(4) Langmuir, Freundlich and Langmuir-Freundlich isotherm model were used for Ni2+ and Cr3+ adsorption isotherm data fitting. The result shows that the adsorption isotherm was a good fit to the Langmuir-Freundlich isotherm, indicating the surface heterogeneity of the adsorbent and coexistence of two kind of adsorption sites in composite.2. Applications of 13X zeolite-activated carbon composite material on coking wastewater with static adsorption method(1) Ammonia nitrogen adsorption on small particle size of composite material is better than size of major ones. But too small partical size is inconvenience and will increase costs in practical application; adsorption feature is"rapid absorption, slow balance"; adsorption equilibrium reached in 40min; removal rate increased gradually with pH value increase; acidic conditions are not conducive to removal of ammonia nitrogen; with the increased initial concentration, adsorption capacity increased but removal rate decreased; adsorption isotherm was a good fit to the Langmuir-Freundlich isotherm. (2) COD adsorption rate is fast, equilibrium adsorption reached in 20min; solution pH had no effect on COD adsorption; adsorption isotherm was a good fit to the Langmuir-Freundlich isotherm.(3) Phenol adsorption also has a"rapid adsorption, slow balance"feature, adsorption equilibrium reached in 20min; with pH increase, removal reduce because of phenol ionized in alkaline condition; adsorption isotherm was a good fit to the Freundlich isotherm.(4) Compared the adsorption capacity with 13X zeolite and activatied carbon, 13X zeolite has remove capcity only on ammonia nitrogen, it's 1.6 times higher than composite materials; activated carbon has remove capacity on COD and phenol and the adsorption capacity is of 2.6 times and 1.9 times higher than composite materials.(5) The actual coking wastewater treatment results show that ammonia nitrogen, COD and phenol removal rate reached 82.8%, 20.0%, 18.9% on composite material.3. Applications of 13X zeolite-activated carbon composite material on coking wastewater with strengthened SBR biological method.(1) Composite materials have significant effect on COD and ammonia nitrogen removal; COD removal rate increased from 40% to 80%, ammonia nitrogen removal rate increased from 70% to 90%, the sludge in the column reduced the settlement time from 25min to 12min.(2) Comparaed with the medium dosage of 13X zeolite and activated carbon, composite material has faster degradation rate in the initial adsorption time.(3) Adding medium on the system to handle high loads phenol has some buffer o maintain the sludge activity.(4) The actual coking wastewater treatment results show that ammonia nitrogen, COD and phenol removal rate reached 77.6%, 62.6%, 56.0% on composite material.