# Green Synthesis Method and Application of NaP
## 1 Introduction  
With the huge impact of global climate change on the human living environment, the clean and efficient use of coal is particularly important. At present, China's clean coal mainly uses coal gasification and other technologies. Coal gasification slag (CGS) is the solid waste generated by the entrained-flow coal gasification technology. According to different pathways of formation, it consists of two forms (coarse slag and fine slag). Coal gasification technology has been widely used for the demand for energy, but the problem of solid waste and water pollution is becoming more and more serious [1, 2]. Ningdong energy and chemical base is one of the most advanced bases for developing clean coal technology in China. In 2018, the base generated nearly 8 million tons of CGS [3]. At present, there is no good treatment method, and it can only be landfilled after high-standard anti-seepage treatment on the ground, which is quite different from the systematic utilization of fly ash [4, 5, 6, 7, 8]. This treatment not only occupies land resources, causes enormous environmental pressure, but also bringshigh transportation and processing costs to the enterprise. Therefore, it is especially important to realize the \"zero emission\" [9] of coal gasification technology and to find ways to recycle CGS.  
At present, there are many researches on the resource utilization of fly ash and slag in the world [7; 8; 10]. However, since the CGS is obtained in a high-pressure vaporization furnace under a reducing atmosphere (CO, H\({}_{2}\)) and 1400-1500 \({}^{\circ}\)C, its structure and composition are greatly different from those of fly ash and slag [3; 5; 9]. Therefore, it is difficult to realize the utilization of CGS by the same method. In this new field, only a few researchers have studied the application of CGS in porous materials, but they have not paid much attention to its resource utilization [11; 12; 13; 14]. Although they have also synthesized excellent porous materials, their preparation process is still considered to have shortcomings such as high production cost, complicated process, easy secondary pollution and high energy consumption. At present, there are many methods for treating wastewater using solid waste, but they cannot be applied on a large scale due to the \"cost and system integration\" problem. Therefore, it is especially important to study a resource-based gasifier slag technology with low cost, simple process, low energy consumption, minimal secondary pollution and high system integration, and this technology will have high application value in the future.  
This study is based on China Ningdong coal gasification coarse slag (CGCS) [3; 15; 16]. We hope to find a feasible way for the utilization of CGCS with the increasingly severe environmental pressure. NaP zeolite is synthesized by a low-cost green template-free method (the best process is shown in Figure 1): CGCS is used as the raw material, no additional silicon-aluminum source is required, and no high-temperature calcination is required. Add a small amount of sodium hydroxide and deionized water and mix well, then age and crystallize. The effects of different molar ratios, aging time, crystallization temperature and other parameters on the synthesis of zeolite were investigated. The crystal type, morphology, specific surface area, and pore structure of the product were analyzed and tested by a characterization method, whereby it was found that the specific surface area of the synthesized NaP zeolite was up to 161.06 m\({}^{2}\)/g. The prepared NaP zeolite was used to remove ammonia nitrogen from simulated wastewater. The effect of pH, adsorption time, and adsorbent dosage on the removal efficiency was briefly studied, and the optimum removal rate was 92.67%. This research can realize the in-situ treatment and utilization of waste generated by the factory, avoid the transportation cost, and realize \"treating waste by waste\", which provides a new way for the recycling of CGCS and the treatment of ammonia nitrogen in industrial wastewater.