The Research On Compost, Potassium Retrieval Of Eichhornia Crassipes And Properties Of Its Fiber Modified Material

Eichhornia crassipes had caused many problems in lakes and rivers in the tropics and subtropics all over the world, and was one of the ten kinds of harmful grass. To make full use of its purification function in eutrophic waters, the most important thing is to transfer its harm of ecologic invasion to utilization of a kind of resource. The amount of Eichhornia crassipes could be digested was very limited by traditional methods, and could not lighten the severe situation. New patterns of utilization need to be found for comprehensive use of this aquatic plant. This paper first investigated the effect of Eichhornia crassipes as a raw material of pig feces compost on the preparation process and the formation of compost quality, its advantage and disadvantage were assessed. On the basic of this work, other new patterns of utilization were investigated. One was the retrieval technology of potassium from the straw of Eichhornia crassipes through the precipitation method, the other was the material research in the transformation of the plant straw to a heavy metal absorbent—xanthogenate of plant cellulose. The main results were list as follows:1. The temperature of 'pig feces+Eichhornia crassipes' treatment was relatively high, its water lose was very fast. The time when the temperature maintained above 40℃was 20 days, less than that of 'pig feces+peat' treatment and 'pig feces+sawdust' treatment which was 27 and 45 days, respectively. As time of composting went on, the content of total N(T-N), total P(T-P) and total K(T-K) increased in general. Available nitrogen(A-N) and A-N/T-N decreased whereas available phosphorus(A-P), available potassium(A-K), A-P/T-P and A-K/T-K all increased. The high content of available K and total K in 'pig feces+Eichhornia crassipes' compost was related with the high potassium conent of Eichhornia crassipes, this was a prominent advantage of Eichhornia crassipes as the raw material/conditioner of compost. The high potassium conent of Eichhornia crassipes was also the reason of the highest pH increment of 'pig feces+Eichhornia crassipes' compost. The result of the high increment of pH was the heavy lose of nitrogen in the form of NH₃, and available N content of the obtained compost was the lowest. The material of 'pig feces+Eichhornia crassipes' compost would become slurry status after several times turning off due to the high water content in Eichhornia crassipes, and the obtained compost became very solid after air drying. These were two kinds of disadvantage for Eichhornia crassipes as compost material.2. The change of humic substance(HS) and humic acid(HA) decreased first and then increased, followed by slow decrease to constant during composting, in general they all increased. HA/HS increased apparently. These were important display of composting maturity and enhanced quality. The increase of pH and CEC of 'pig feces+Eichhornia crassipes' compost was the highest, and the increase trend of HA/HS was the lowest among these three kinks of compost, these were related with the high mineral nutrients contents of Eichhornia crassipes. There existed a positive correlation between the change of pH and cation exchange capacity(CEC), a negative correlation between the change of HA/HS and CEC, this meant the change of pH and HA/HS after compost may be two indicators in evaluation of the change of CEC.3. In general, except the content of extractable Cr, the content of most 1mol/L NH₄Ac-0.05mol/L EDTA extractable metal ions increased, the order of increase extent was 'pig feces+Eichhornia crassipes'＞'pig feces+sawdust'＞'pig feces+peat'. In 'pig feces+Eichhornia crassipes' compost, the heavy metals with relatively high content, As and Cu, mainly come from pig feces, the heavy metals from Eichhornia crassipes have little influence on the heavy metal contents of the compost.4. Extraction with 0.80mol/L HC1, volume ratio HC1: weight of sample=5:1 could get 70.0ï¼…K of the stem-leaf sample of Eichhornia crassipes in the extraction solution. 4 mol/L NaOH was used to adjust the acidity of the extracted solution from stem-leaf sample. When the pH of the solution increased to about 13, most of the soluble organic substances, Ca²⁺ and Mg²⁺ were precipitated togother. After filtration, 88.0ï¼…of K was obtained in the obtained filtrate. When molar ratio n(H₂C₄H₄O₆)/n(K⁺)=1.72 and the sediment-solution system was placed in 0℃for 3h, 72.3ï¼…of K in the filtrate solution could be obtained in the solid precipitant, the content(or purity) of KHC₄H₄O₆ in the coarse precipitant was 88.4ï¼…. Generally, 44.5ï¼…of K in the stem-leaf sample of Eichhornia crassipes could be retrieved in potassium salt.5. The cellulose content of Eichhornia crassipes, Alternanthera philoxeroides, Huanan fern, rice straw, rice root, rice shell were very similar, but the benzene-ethanol extracted content and hemicellulose of Eichhornia crassipes were higher than other plant straw, especially for the stem & leaf parts of Eichhornia crassipes. And the lignin content of Eichhornia crassipes was apparently lower than that of other plants, especially for the stem & leaf parts of Eichhornia crassipes. The copper adsorption ability of the stem & leaf parts of Eichhornia crassipes, was the highest among all the original plant materials, and the copper adsorption ability of the xanthogenate made from the stem & leaf parts of Eichhornia crassipes, 165.95±8.27 mg/g, was also the highest among all the xanthogenate made from plant materials. Alkaline treatment had little influence on the copper adsorption ability of the plant material, even decreased their adsorption ability. But the further CS₂ treatment increased their copper adsorption ability significantly for the stem & leaf parts of Eichhornia crassipes, the root part of Eichhornia crassipes, Alternanthera philoxeroides, rice straw, and microcrystal cellulose. The copper adsorption ability's order of these xanthogenate was, the stem & leaf parts of Eichhornia crassipes＞rice straw＞Alternanthera philoxeroides＞microcrystal cellulose＞the root part of Eichhornia crassipes.6. The X-ray diffraction patterns indicated, except for the original materials with high crystal content, rice straw and rice shell, the crystal content of original plant materials were enhanced through alkaline treatment, and the crystal content of alkaline extracted cellulose were decreased by further CS₂ treatment. The results of TGA/DTA indicated, the exothermic peak of the plant materials were transferred to higher temperature through alkaline treatment and further CS₂ treatment. This indicated that the thermo-stability of the plant materials were enhanced gradually. The decomposition process of aquatic plant material were more complex than that of three rice serial, the former were more thermo-stable.7. FTIR results indicated, original material of aquatic plants, especially for the stem & leaf parts of Eichhornia crassipes, had relatively more active function groups for adsorption. Most of lignin, polyxylose with low molecular weight, ere, were removed from original plant material after alkaline treatment, and the absorbance peak decreased in all range of wavenumber. After CS₂ treated, the absorption of new function group-C=S, -O-CS-S-appeared on the basic ofβ-(1→4)-glycosidic linkages in the xanthogenate. Compared to alkaline extracted cellulose, the FTIR spectra change of xanthogenate made from the stem & leaf parts of Eichhornia crassipes, the root part of Eichhornia crassipes, Alternanthera philoxeroides, and rice straw were more obvious, these results were in accordance with the copper adsorption ability of these xanthogenates, and indicated the apparent superiority of these aquatic plants and rice straw as the original material for preparation of xanthogenate, in which aquatic plant had better potential compared to rice straw due to the better thermo-stability of the former.