The Research On Preparation Of Functionized Coconut Shell Activated Carbon And Cadmium Absorption

Heavy metal pollution in water has become a global environment pollution issue, more and more countries and regions have considered the prevention of heavy metal pollution as a priority of the work plan. Sources of the heavy metal including:metal mines, non-ferrous metal smelting, steel, electroplating, petroleum chemical industry, leather making and photograph industries. The methods for heavy metal ion removal in wastewater involve physical methods, chemical methods, biological methods as well as new composite approaches. Adsorption method is one of the physical methods, which has attracted a lot of attention for its simplification, low operating cost, and good adsorption performance.In this paper, modified activated carbon technology was introduced. The modified coconut activated carbon was functionalized with HNO3, H2O2oxidation method followed by NH3H2O soaking, pyridine soaking or NH3pyrolysis processing. The physicochemical properties of the modified adsorbent and its adsorption characteristic of Cd2+from wastewater were studied.The scanning electron microscopy (SEM), infrared spectrometry (FTIR) and BET surface area determination are used to characterize the physicochemical properties of the modified activated carbon. Impacts of contact time, initial metal ion concentration and adsorbent dosage on the effect of adsorption are examined to explore the method of improving activated carbon adsorption capacity of heavy metals.SEM images showed that the modified activated carbon had a significant increase of pores with a uniform distribution. The sample which treated by HNO3(ACN) had more pore volumes and bigger BET surface area than that treated by H2O2(ACH). NH3H2O made the surface of ACN became rough and with an average pore width of2.6639nm. However, pyridine made the surface smooth and with a average width of3.2063nm. FTIR spectra provided the evidence that coconut shell activated carbon was successfully coated on the surface of oxygen groups and nitrogen groups after soaking in HNO3. And the pyridine soak could introduce acylamino to the surface of activated carbon. In the experiment of adsorption of Cd2+on the functionalized activated carbon. The equilibrium of adsorption was reached equilibrium within4h. The cadmium removal efficiency increased with the increase of adsorbent dosage. The metal adsorption capacity increased while the removal efficiency of cadmium decreased when the initial zinc ion concentration enchanced. The second dynamics can better fitting equilibrium data. The equilibrium data were modeled by the Langmuir and Freundlich models. The results demonstrate that the Langmuir model fits better than the Freundlich model for the adsorption equilibrium data in the examined concentration range of10-1000mg/L. After modification, all of coconut shell activated carbon samples had greatly increases in adsorption capacity. The maximum adsorption capacity of sample treated by HNO3and25%NH3H2O (ACNYBD), treated with HNO3and13%NH3H2O (ACNBNH), treated with HNO3and99.5%pyridine (NYBD) and treated with HNO3(ACN) were35.0mg/g,29.1mg/g,172.9mg/g,61.8mg/g. The pyridine soak samples NYBD has the highest adsorption capacity which reached172.9mg/g.