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Abstract:Composting is considered to be the primary treatment method for livestock manure and rice straw, and high degree of maturity is the principal requirement for safe land application of composting product. In this study pilot-scale experiments were carried out to characterize the co-composting of livestock manure and rice straw, as well as to establish a maturity evaluation index system for the composts obtained.Two pilot composting piles with different feedstocks were conducted for 3 months: (1) swine manure and rice straw (SM-RS); and (2) dairy manure and rice straw (DM-RS).During the composting process, parameters including temperature, moisture, pH, total organic carbon (TOC), organic matter (OM), different forms of nitrogen (total, ammonia and nitrate), and humification index (humic acid and fulvic acid) were monitored in addition to germination index (GI), plant growth index (PGI) and Solvita maturity index. OM loss followed the first-order kinetics equation in both piles, and slightly higher OM mineralization rate was achieved in SM-RS pile. Also, SM-RS pile exhibited slightly better performance than DM-RS from the evolutions of temperature, OM degradation, GI and PGI. The C/N ratio, GI and PGI could be included in the maturity evaluation index system in which GI > 120% and PGI >1.00 signal mature co-composts.

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Magnetic biochar/ZnS composites were successfully synthesized by deposition of ZnS nanocrystals (NCs) on magnetic biochar in a polyol solution. The as-prepared composites showed a high maximum adsorption capacity for Pb (II) up to 367.65 mg g −1 , which was 10 times higher than that of reported magnetic biochar. Furthermore, the lead-laden magnetic biochar/ZnS composites can be easily separated from the solution by a magnet after adsorption because of the excellent superparamagnetic properties. The composites were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The adsorption process was well described by the pseudo-first-order model, and the adsorption isotherm could be well fitted by the Langmuir model. The thermodynamic studies showed that the removal of Pb (II) was an endothermic and spontaneous process. The present results warrant the promising application of magnetic biochar/ZnS composites in removal of Pb (II) from contaminated water.

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