Study Of Non-recycling Water Culture Improvement And Active Carbon Regeneration

Currently, nutrient solution is recycled in most water culture to provide enough oxygen and prevent toxicity caused by accumulation of root exudates, but this is not only wasteful but spread diseases. Studies were carried out to use still solution culture with air pumps to provide oxygen and activated carbon to adsorb root exudates and to simplify culture facilities. The results showed that activated carbon and airing could increase lettuce yield with the best being 2-4 hr of airing and 60-120 g of activated carbon. The highest lettuce yields were obtained with treatments of 2 hr airing plus 60 g activated carbon and 4 hr airing plus 120 g activated carbon. Airing and activated carbon had significant effect on later stage growth of lettuce but not on the early stage growth. When airing time was short, nitrogen content in lettuce increased proportionally with increasing activated carbon in solution, but no such relationship was found with long airing time. Nitrogen and K contents decreased in the later stage growth of lettuce.Chemical methods and microwave radiation were used to regenerate phenol-adsorbing activated carbon. For chemical methods, neither ethanol nor water could regenerate phenol-adsorbing activated carbon, while sodium hydroxide was effective using a carbon.solution ratio of 1:25 at 70-80 ℃ for 2 hr with the regenerated activated carbon possessing an adsorption ability of 10.0 ml/0.1g. Microwave radiation could effectively regenerate activated carbon when water was used as fire inhibitor with a carbon.water ratio of 1:1 for 9 min under a power of 680 W or 1160 W, or without water under a power of 810 W. The adsorption ability of the activated regenerated by microwave radiation could be up to 11.0 ml/0.1g. Microwave radiation was proved to be an economical and practical activated carbon-regenerating method with short regenerating time and high efficiency.