Study On Properties Of Biochar Made From Household Biowaste

The quick process of urbanization has caused increase of waste production. And the waste has caused environmental pollution without treading correctly. Handling household bio-waste has become our country and the world a major environmental problems. Burning was used as a refuse resources, reduce, harmless handling method to hand household bio-waste.But its process has caused secondary pollution to environment. A safety and efficient method urgently need to explore now. It has attracted much attention and research recently on Pyolysis Gasification Technology which was thinked as a better method to slove waste. This technology is also in laboratory study phase and the product’s application is a blank. This study compared household bio-waste bichar with agricultural waste bichar in order to discuss chemical and physical properties, adsorptive characteristics of heavy metals, and heavy metal content and form of distribution. We hope that it can provide a scientific basis for biochar and recycle of biowaste. The main results as follows:1. The partial size smll than2mm accounted for more than95%. The bulk density of biochar was in0.55-0.65cm-3·g-1. There were no difference of pH value, EC and CEC in different batches. The pH value were in8.23-8.30, EC were in5.70-5.84mS·cm-1, CEC were in293.33-299.20cmol-kg-1. There were no difference in total functional groups among biochars. The total functional group were in4.27-4.43mmol·g-1, and the alkaline oxygen functional group were significantly bigger than the acidic oxygen functional group.The organic carbon content were in204.2-222.7g·kg-1. There were no significantly differences in total organic carbon, as the same as in the N, P, K. The water soluble matter content were in16.56-23.06g-kg-1. There were no difference in available P, K, NH4+-N and NO3--N. The CV were smaller than15%in chemical properties, while bigger than15%in fertilizer content.2. An experiment was conducted on Cd (II) and Pb (II) adsorption in solution by biochar produced with pyrolysis of household biowaste. The effects on Cd (II) and Pb (II) removal from solution of adsorbent contact time, initial Cd (II) and Pb (II) concentration, adsorbent dosage, solution pH as well as the particle size of biochar diameter were investigated. The results showed that the adsorption kinetics of Cd (II) and Pb (II) could be better described by pseudo second order model, and approached equilibrium after lh. The adsorption curves followed an isothermic adsorption model, which could be better described by Langmuir model than by Freundlich model on Cd (II). The maximum Cd (II) adsorption capacity at25℃reached6.22mg·g-1by as estimated by the Langmuir model. But both adsorption model were not good at describing Pb (II) adsorption. The removal proportion of Cd (II) and Pb (II) was seen increased with increasing dosage of biochar. While solution pH affected the Cd (II) adsorption capacity, the increase in solution pH was positively proportional to biochar rate and negatively to the initial pH both on Cd (II) and Pb (II) adsorption. This study suggested a potential use of biochar from household biowaste in removing Cd (II) and Pb (II) in polluted water.3. Heavy metal analysis result was as follows:BC2had the highest Cd, which significantly higher than BC2. While BC1had the highest amount of Pb, Cu, Zn, Mn, and the BC4’s Cd was the highest in different batches. Ni and Cr content was the highest in BC3. There were significant difference of each element (Hg except) among different batches of biochars. The Pb had the biggest range in CV, which index is31.52%. The CV of Cr、 Cu and Ni were in25-30%, the rest mental’s C V was ahout10%.There were only Cd, Pb, Cu, Zn, Mn and Ni was determined by DTPA extraction. The DTPA extraction state of Cd and Pb accounted for about12%and Pb20%respectively. The continuously multilevel chemical extraction method and dutch heavy metal leaching out toxicity test method were used to research on biochar leaching characteristics and toxcity. The result was that:Cd, Pb, Cr, Cu mainly existed in the form of residue state, and the percentage of the total were40%,50%,94%and75%. The second part was the crystal oxidation iron state. Different standards were used in the evaluation of heavy metal pollution degree. The results showed that biochar from household bio-waste full comply with fly ash and agricultural sludge agricultural standard, but beyond the standard of agricultural waste. Single factor pollution index method was also used.The index showed that Cd elements out of limits and exceeded bid. Other heavy metal elements polluted a small degree.