Abstract:
In Thailand from 2015 to 2016, 88% of spent batteries are Lead-acid batteries (LABs) in which their main composition (lead and plastic) are recyclable. Whilst, sulfuric acid treatment is not uninterested issue. A typical method for treatment of spent acid before discharge is neutralization and subsequently the precipitate from this neutralization are then landfilled. This research focuses on the comparison of spent sulfuric treatment methods. The material flow analysis was used as an evaluation tool to estimate the number of spent LABs and sulfuric acid. The material flow analysis revealed that the exporting of LABs is larger than importing. The proper management of spent LABs is also increasing due to tax incentive policy. Regarding the factors influence the quality and quantity of gypsum precipitation by the reaction between H2SO4 and Ca(OH)2 in a batch system, the result showed that the quantity of calcium sulfate depends on the pH value of the solution. Most precipitates are gypsum with a monoclinic crystal pattern. With increasing the concentration of sulfuric acid, plate-like crystal size decrease while needle-like and rod-like crystals are growing more and their lengths also increase. Thus, precipitates of spent sulfuric acid from traction battery with 10% Ca(OH)2 showed that metals in spent sulfuric acid affect both quality and quantity of gypsum. This precipitate has a smaller crystal size than natural gypsum but its crystal pattern still is the same. The environmental impact of each treatment method including, regeneration, neutralization, and recycling of gypsum, were considered within the system boundary of Gate-to-Gate. The functional unit is 1 ton of spent sulfuric acid. A software used in this study and research methodology were SimaPro 8.3 and CML-IA baseline. The main environmental impacts of those treatment methods were human toxicity, fresh aquatic ecotoxicity and acidification. Electricity consumption, landfilling of solid waste and wastewater generation were the key parameters in each treatment method.