Preparation Of Biochar From Aquatic Eco-remediation Plants And Their Sorption On Ammonium And Phosphate

It is well known that increased nitrogen (N) and phosphorus (P) inputs have resulted in accelerated water eutrophication worldwidely. Eutrophication in lakes, reservoirs, estuaries and rivers is a common environmental issue, especially in the developing countries like China. Thus, cost-effective and highly efficient water treatment technologies are desirable. Constructed wetlands have emerged as a promising approach owing to their bioremediation potential. Both terrestrial and aquatic plants have been utilized to remove N and P from wastewater. However, wetland plants will release nutrients back into the water by decomposition processes if the plant were not harvested and disposed properly. Thus, properly harvest and handle the plantsis very important. Harvested plant biomass can be used as livestock feed, or converted into usable energy through other pathways, like bioethanol, biogas, biochars. Biomass is one of the largest sustainable energy sources in the world. The utilization of biomass for energy production has gained increasing popularity in some countries because it can reduce the risk of energy shortage. Biochar is a pyrogenic carbon-rich material produced from biomass, in particular agricultural wastes such as corn, sugarcane bagasse, peanuts, etc. The production and use of biochars has been for centuries, it developed pore structure and surface functional groups,has a wide range of applications in various fields. Preparation of biochars in different ways,usually the first carbonization and activation, the activation has physical activation,chemical activation and the catalytic activation three methods. Physical activation is only without external additive method, the advantage is that there is no secondary pollution problems.Many studies have evaluated the use of biochar as adsorbents for the removal of heavy metals, pathogens and other pollutants in wastewater. However, research on nutrient removal, particularly ammonium and phosphate, from water by biochar is limited. In this study, we investigated ammonium and phosphate sorption by selective biochar derived from four phytoremediation plants (Salix rosthornii Seemen, T. dealbata, V. zizanioides and Phragmites (sp.)) which were subjected to three different temperatures (500,600, and700℃) through slow pyrolysis. The biochar were characterized via elemental analysis, surface area analyzer, fourier transform infrared, scanning electron microscopy. We evaluate the potential of pyrolyzed biochar for ammonium and phosphate removal from aqueous solution and sorption mechanisms. The results showed:1. All of the tested twelve biochar have large surface area. Surface area, carbon content, the value of pH increased with increasing temperature, whereas the yields, CEC, H and O contents decreased. The Ca content of all biochar was similar regardless of temperature, but TC (biochar of T. dealbata) had a high content of available P and Mg, approximately three times greater than the other biochars. TC600(biochar of T dealbata under600℃) has more functional groups than other kinds of biochars under600℃.2. All the biochar were efficient materials for ammonium removal. The sorption capacity increased with the increasing concentration of ammonium. Among different plant biochar produced under same temperature, CEC is the most important factor for ammonium sorption. However, with an increase in activation temperature for biochar from a given plant, surface areas also affect sorption. From SEM no significant differences were found between TC600, TC600+P, and TC600+NH4.3. TC had a greater phosphate sorption capacity than the other adsorbents but released some phosphate back into solution The greater phosphate removal by TC probably due to its Mg content, which can precipitate phosphate in aqueous solutions. For biochar derived from a given plant, the surface area increased with the activation temperature, but the Mg content remained relatively constant. Therefore, changes in phosphate removal are likely due to interactions with the surface area, in the same plant biochar.