The Research Of Modified Biochar Direct Reduce NO

Biochar is a carbon-rich, low-density, insoluble and highly-aromatic material that is prepared with thermal treating carbon-rich biomass in absence of oxygen. In this experiment, two types of hazardous wastes, Heavy metal accumulated plants and municipal domestic sludges, used to be prepared for biochar and reduce the NO in order to achieve the aim of waste controlling by waste. Explore the NO removal efficiency via different preparing temperature, different NO reactive temperature and different laden conditions. Besides, element, BET, SEM, TPD and XPS are used for analyzing the different samples. The result of the experiment as followed.(1) The heavy metals in copper-containing Ricinus communis L.(RC) biomass obtained from soil remediation showed a low content, which have little efficiency on direct reducing NO by biochar. The effect biochar direct reduce NO is influenced by the prepared temperature and NO reaction temperature. The biochar obtained in 700 oC have a high efficiency, almost 17.66 μmol/g·min, compared with that obtained in 500 oC. In this paper, the process of NO reduction during 300- 600 oC by biochar in 700 oC is fitting with Arrhenius equation that can describe the relationship between the rate constant of NO reduction and reaction temperature and the equation is k=2.8×108×exp(-3240/T).(2) In this paper, heavy metal accumulated biochar with a high Cu content was prepared by RC biomass adsorbed Cu, which leaded the result that with the content of heavy metal increasing, the inhibitory effect of copper on the NO reduction by biochar was gradually increasing. However, the high polysis temperature could alleviate the inhibitory effect of copper. SEM and TPD analysis were used for exploring copper inhibited NO reduction. The possible reasons as followed. On the hand, Copper coverd on the surface of biochar reduced the reaction active site C* on the surface of biochar interacting with NO. On the other hand, the presence copper reduce the amount of CO released from biochar heated, which weakens the gas phase reduction process of NO.(3) The result of the efficiency reduced by RC biochar adsorbed Cu showed that with the amount of Copper adsorption increasing, the effect of copper on the NO reduction by biochar was gradually decreasing. The copper adsorped on the surface of biochar mostly exist as Cu(OH)2 which have no acivity for NO reduction. Simultaneously, the process of biochar adsorb Cu would result in the inherent alkali and alkaline metal(AAEM) species dissolution and the catalysis of NO reduction would loss in the absent of AAEM. The surface area was a key factor determining the efficiency on reducing NO when comparing activated carbon powder adsorbed Cu.(4) the content of N in sewage sludge can be improved by adding inorganic ammonia and organic urea in the hydrothermal process. The N content of organic urea modified hydrothermal carbon was higher than that of inorganic ammonia with adding the same molar mass. The increase of hydrothermal temperature is beneficial to the load of N. The XPS showed that increasing the hydrothermal temperature could promote the NH2 and N5 functional groups on the surface of hydrothermal carbon converting to a more stable structure such as N-Q and N6.(5) The sluge hydrochar modification with inorganic ammonia and organic urea can promote the NO reduction effect. Inorganic ammonia modification can promote hydrochar in the range of 150 ~ 300 oC on NO reduction and the maximum NO removal efficiency could reach 80 %. Organic urea modified mainly promoted hydrochar in 360 ~ 450 oC temperature on NO reduction and the maximum no removal rate is about 73 %. In this paper, the reduction of NO at different reaction temperatures by hydrochar obtained by the ammonia and urea modification under the condition of 280 oC was fitted with the Arrhenius equation. The formula for the conversion rate of NO and reaction temperature were as follows: k=9.5×106×exp(-1201/T) and k=1.1×107×exp(-1515/T). Through the hydrochar NH3-TPD, it is found that the low stability NH2 thermally decomposing was the main factor resulting to the high efficiency on NO removal during 150 ~ 300 oC and The decomposition of more stable nitrogen containing functional groups is the main reason for the increasing of NO removal efficiency during 360 ~ 450 oC.