Experimental Study On The Adsorption Release And Controlled Release Performance Of Nutrients From Photosynthetic Hydrogen Production Tailing Solutio

This study was conducted under the funding of "Research and Demonstration of Waste-Based Co-production Technology of Biohydrogen and Biomethane and SlowRelease Nutrients"(Project No.2018YFE0206600).Zeolite was used as an adsorbent to recover NH4+ and K+ nutrients from photosynthetic hydrogen production tailings,and the adsorption and release characteristics of zeolite on NH4+ and K+ in photosynthetic hydrogen production tailings were investigated.Then the zeolite base fertilizer was prepared by mixing the attached zeolite with nutrients and using a binder,and then the zeolite base fertilizer was coated with lignosulfonate and alkaline lignin to achieve nutrient controlled release.The effects of different binders,coating materials and particle size of zeolite-based fertilizers on the nutrient release control performance were investigated.Finally,the zeolite-based fertilizers were prepared for planting trials by obtaining the zeolite-based fertilizer preparation process that is suitable for the nutrient release and the fertilizer demand characteristics of three vegetables,and the effects of zeolite-based fertilizers on vegetable growth and soil after application were analyzed.The main research results are as follows:(1)The zeolite adsorption release of NH4+ and K+ from the simulated tail liquor of photosynthetic hydrogen production was consistent with the basic pattern of zeolite adsorption release of NH4+ and K+ from the tail liquor of photosynthetic hydrogen production.The adsorption processes of zeolites on NH4+ and K+ were in accordance with the quasi-secondary kinetic model.The adsorption process of zeolite on K+ is consistent with the Langmuir adsorption isotherm model.both Langmuir and Freundlich isotherm adsorption models can describe the adsorption of NH4+ on zeolite well.The nutrient release from attached zeolites showed a trend of rapid release and slow equilibrium,and the nutrient release rate(release amount)increased gradually with the increase of temperature,where the effect of temperature on NH4+ release was not obvious.(2)The zeolite-based fertilizer prepared using Au-bearing clay as binder showed the best forming effect.The maximum molding rate of 86.87% and the minimum disintegration rate were observed for zeolite-based fertilizers prepared with ≤88 μm particle size attached zeolite,while the minimum molding rate of 72.33% and the maximum disintegration rate were observed for zeolite-based fertilizers prepared with 105-125 μm particle size attached zeolite.The highest forming rate of zeolite-based fertilizers prepared using different binders was89.86%(oxidized starch as binder)and the smallest disintegration rate was 4.12%(alabaster as binder).(3)The total nutrient release rates of all the prepared finished zeolite-based fertilizers exceeded 80%,and the imposed process was obtained for the preparation of zeolite-based fertilizers using three vegetable growths.The zeolite-based fertilizers prepared with ≤88 μm attached zeolites(4-4.75 μm)released NH4+ for 15 d and K+ for 12 d after coating,and both were released in large amounts in the first 6 d,which were suitable for the fertilization characteristics of cabbage.In contrast,the release time of NH4+ and K+ was 18 d and 15 d for zeolite-based fertilizers(2.5-4 mm)prepared with 105-125 μm attached zeolites,which were suitable for the long growth period of Chrysanthemum coronarium.In contrast,coriander has the longest growth period and can be applied in batches using zeolite based fertilizers(2.5-4mm)prepared from 105-125 μm attached zeolites.(4)The application of zeolite-based fertilizers promoted the growth of vegetables and avoided the harm caused to the soil by the application of compound fertilizers.It effectively slows down the process of soil acidification and improves soil enzyme activity(soil fertility)and soil microbial diversity to a certain extent.In the early stage of compound fertilizer application,nutrients were released in large quantities,and unused nutrients penetrated into the bottom of the planting box and even flowed out of the box,so the nutrient content that vegetables could absorb was low,while the nutrient content that vegetables could absorb in the late stage of zeolite-based fertilizer application was high.The growth of vegetables with zeolite-based fertilizer was better in the later stage,and the net photosynthetic rate and chlorophyll content were lower than those with compound fertilizer in the early stage and higher than those with compound fertilizer in the later stage.This study provides theoretical and technical references for the preparation and application of zeolite-based fertilizers based on nutrients in the tailing solution of photosynthetic hydrogen production.