Preparation of Activated Carbon by Agricultural Straw and Study on its Performance

Abstract

The activated carbon is a kind of adsorbents which has ample internal pore structure and high specific surface area, widely applying on chemical industry, pharmaceuticals, metallurgy industry, agriculture and environmental protection. The effects of operation parameters such as impregnation ratio, activation temperature and time on the adsorption properties of activated carbons,and burning time were measured and analysed in order to optimize these operation conditions. We can make such conclusions: The optimum technological conditions of preparation by chemical activation were: KOH / ZnCl2 was the better activator, activator ZnCl2 5mol/L, solid/liquid 1:1g/mL, soaking time 1.0h, soaking temperature 20°C, pyrolysis temperature 550°C,the optimum washing temperature 90°C. Introduction With the improvement of people's linving standard in our country, environmental problems also rise sharply. Adsorption method is widely used, as a kind of waste water and gas pretreatment method [1].In numerous adsorbents, activated carbon [2] is a good choice. China is an agricultural country, so its crop straw resource is very rich in it. There are plenty of rest straw biomass except for return to the field [3].In recent years, crop straw burning phenomenon becomes more and more serious, and it has caused to great harm for environment. Using maize straw preparation of activated carbon [4], not only can solve the problem of a large number of corn straw comprehensive utilization, but also improve the resource utilization. This experiment used straw as its raw material [5], the adsorption value of methylene blue solution and the activated carbon yield as its measurement index. First screening of activator, then explore effective activator by changing solid-liquid ratio, activation time, activation temperature, pyrolysis time and other factors[6],perfect the preparation technological parameters of chemical activation method. This article also discusses the adsorption performance of straw activated carbon, provides the technically feasible reference. Materials and methods Materials Corn stover Instrument: Multi-parameter electrochemical analyser (DR 5000 type), electronic balance (AUY220 type), oven oscillator (CHA-S type), temperature controller (KSW-4D-11 type), electrothermal constant temperature water bathpot (DK-S24 type), ultrasonic cleaner (KQ-250DB type). Reagent: 37% hydrochloric acid solution, 98% sulfuric acid solution, methylene blue(A.R), potassium hydroxide(A.R), sodium hydroxide(A.R), phosphoric acid(A.R), zinc chloride(C.P) . Experimental method Dipping and activating the corn straw by adding activator such as inorganic salt (eg. H2SO4、 ZnCl2、H3PO4), then carbide it in a certain temperature. Activated carbon could be got by cativating finally. Because the influencing factors are different, such as the carbonization time, International Power, Electronics and Materials Engineering Conference (IPEMEC 2015) © 2015. The authors Published by Atlantis Press 957 activation temperature [7], activation time and activator concentration, it could be get activated carbon of different pore-size ranges. Put the corn straw into the stoving chest after grinding it (105 °C,24h), weight 1g straw and adding some activator. Put it into the high temperature tubular resistance furnace [8], control the condition: heating rate 20°C/min, pyrolysis temperature 450700°C, pyrolysis time 0.5-2.0h. Protect the experimental process by controlling the N2 [9] flow rate at 0.1m3/h. The production has been cleaning in turn by 3mol/L hydrochloric acid solution, 70 °C distilled water till pH is 6-7, ultrasonic cleaner(50W,10min).Put the sample into dying oven at 120°C for 5 hours, grinding and get the final production through 200 mesh sieve. Results and Discussion Effect of Activation temperature Put the corn straw into the oven after grinding it, and the experimental condition is: activation time 1.0h, ZnCl2 5mol/L,KOH 5mol/L,ZnCl2/KOH=1/1,adsorption time 0.5h.Then it could be get the effect of activation temperature from graph 1.As a result, temperature effect on the performance of the activated product is obviously, and the best activation temperature is 20°C. Table 1 Effect of activation temperature Activation temperature(°C) Yield (%) Methylene blue adsorption value(mg/g) 15 35.47 37.42 20 30.83 38.04 30 30.11 32.18 35 28.45 31.33 Yield Methylene blue adsorption value Fig. 1 Effect of Activation temperature Yield Methylene blue adsorption value Fig. 2 Effect of Activation time 25 27 29 31 33 35 37 39 10 15 20 25 30 35 40 30 31 32 33 34 35 36 37 38 39