Adsorption Of Microcystin-LR On The Leaves-phyllostachys Praecox-derived Biochar And Its Preparation

Biochar is a material with highly porous structure and high carbon content generated from biomass pyrolysis under anaerobic or oxygen-free conditions, which has a notable impact on the migration, transformation process and bioavailability of contaminants in the soil and water. Therefore, the relationship between the structural characteristics and adsorption of biochar has become a hot topic in environmental chemistry studies. This article introduced research advance on structural features, adsorption property and mechanism of biochar; adopted a typical agricultural waste, hyllostachys praecox leaves, to develop a new type of biochar as response to the increasingly serious microcystin pollution in natural water and soil, and explored the adsorption mechanism of microcystin-LR on this renewable adsorption material; discussed the impacts of adsorption conditions and organic matters on the adsorption of microcystin-leucine-arginine on hyllostachys praecox leaves biochar to optimize the preparation process. The major results are presented as follows.(1) Screening the optimal preparation condition of the biochars. Compared respectively the adsorption capacity of MCLR on the biochars which were generated by controlling heating rate are5K/min,60K/min and pyrolysis temperature are150℃,300℃,400℃,550℃. The results showed that adsorption properties of the biochars vary under different heating rates and pyrolysis temperature, the biochar was produced under heating rate is60K/min and pyrolysis temperature is550℃has a stronger adsorption capacity of MCLR and the maximum adsorption capacity up to624.47μg/g, adsorption capacity has a decline when elevated reaction temperature and pH, and the concentration of dissolved organic matter increases.(2) Characterized structural differences of adsorption properties of MCLR on the biochars. Elemental analysis showed H/C and (N+O)/C of biochars decreases with pyrolysis temperature increasing, indicated that aromatic increased and polarity decreased with the deepening of charring, which also resulted in an increase of its adsorption capacity; the results of BET-N2surface find the biochar’s specific surface area increase rapidly with the rising of pyrolysis temperature and heating rate, which is a reason for biochar’s adsorption capacity increases; the results of scanning electron microscopy showed that the richness of gap structure increase rapidly with the rising of pyrolysis temperature and heating rate, and increses adsorption capacity.(3) Discussed the adsorption behavior of MCLR on the biochars. Based on the adsorption kinetics and adsorption model and found the adsorption behavior of MCLR on the biochars was related to its preparation conditions, adsorption mechanism of the biochar prepared under low heating rate and low thermal decomposition temperature is dominated by partitioning, the adsorption kinetics fitted well with Pseudo-first-order equation (R2=0.989-0.990), adsorption of the biochar under high heating rates and high pyrolysis temperature is adsorption-dominante, and adsorption kinetics characteristics fitted well with Pseudo-secondt-order equation (R2=0.985), and adsorption behavior of MCLR on the biochars can be described well by Freundlich model (R2=0.989～0.990).