| At present,environmental damage is becoming serious,and resource reserves are getting smaller.Plants have already undertaken some functions of repairing environmental pollution and providing energy.Such as using plant enrichment heavy metals in water to purify water,carbonizing plant into charcoal materials,to instead of expensive activated carbon to adsorb heavy metals in water.It can also be used for electrochemical energy storage,as an electrode material for super capacitors.Water hyacinth has a wide source,low price,large biomass,rapid reproduction,and unreasonable treatment can lead to biological invasion,bring ecological damage,and directly throw away waste biological resources.In this paper,water hyacinth is used as research object to study the enrichment and purification ability of three heavy metals in water,and bio-carbon is prepared by different methods to adsorb hexavalent chromium and supercapacitor electrode materials in water.as follows:(1)By the static hydroponic method experiment the ability of removing heavy metals(Fe,Coand Ni)in short duration by Water hyacinth was investigated.The results showed that the short duration ability of the three heavy metals in water hyacinth was Fe≥Co>Ni;The enrichment of heavy metals reached equilibrium within 6d.And the lower the initial ion concentration,the better the purification ability.When the initial concentration is less than 3 mg/L,the removal rate of Fe and Co is more than 80%.The water after enrichment the heavy metal content of the root of the gourd is several times the sum of the stem and the leaf.The root plays a significant role in the purification process.In practical use,it is suitable for treating low-concentration Fe and Co contaminated wastewater,and needs timely salvage to improve removal efficiency.(2)The water hyacinth biochar was prepared by rapid pyrolysis for 10 min under nitrogen atmosphere to simulate the adsorption of hexavalent chromium in water.The experiment showed that the adsorption effect of water hyacinth biochar was the best when the pyrolysis temperature was 400℃,and the lower pH of the solution was beneficial.The adsorption reaction was carried out.At pH=1,C0=100mg/l,the treatment effect of WHBC400 reached 99%;the adsorption isotherm conformed to the Redlich-Peterson model,and the adsorption kinetics followed the pseudo-secondary adsorption kinetics model;at different temperatures(The reaction equilibrium constants at 45℃ were found to be the highest at 25 ℃,35 0C,and 45 ℃.The adsorption mechanism of water hyacinth biochar was analyzed by various characterization methods.The results showed that the main influencing factors of water hyacinth biochar adsorption of Cr(Ⅵ)in water were as follows.It is a functional group in which a carboxyl group plays a large role in the adsorption process.(3)Using water hyacinth biomass as precursors,it is biochar materials were prepared by one-step carbonization activation in KCl and NaCl mixtures.The carbon yield ratio after direct mixing and covering method was about 10%higher than be directly covered.The mechanism of action of molten salt in carbonization activation process is analyzed by TG-DSC.The specific surface area and X-ray diffraction analysis showed that the biochar layer of the water hyacinth leaf was the thinnest,the bulk structure was the smallest,and the specific surface area was 582.81 cm3/g,which was dominated by micropores.There is a graphitized structure and abundant oxygen-containing functional groups in the sample.The electrochemical performance of water hyacinth leaf biochar was the best in electrochemical test.The specific capacitance was 122 F/g when the current density was 1A/g,and the capacitance retention was 67.2%when the current density was 10 A/g.When assembled into a symmetrical dual-stage capacitor,the specific capacitance at a current density of 0.5 A/g is 63 F/g,and the energy density is up to 4.375 Wh/kg,at which point the power density is 0.035 W/kg. |
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