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Keywords: purification of quartz sand, acid washing, special adsorption materials, wastewater reuse. With the development of industries such as fiber optics, microelectronics, and solar energy, high-purity quartz sand, as an important raw material, has become increasingly significant. Impurity elements in quartz sand can significantly affect the properties of quartz products; transition metals such as iron can influence the light transmittance and electrical conductivity of quartz products ； Excess levels of alkali metal impurities such as potassium and sodium can reduce the high-temperature resistance of quartz products, thereby affecting their thermal stability and optical properties. To obtain quartz sand of extremely high quality, it needs to be purified. Acid washing is an essential step in the purification of quartz ore. It takes advantage of the fact that quartz is insoluble in acids, while other impurity minerals can be dissolved by acidic solutions, thereby enabling the separation and purification of quartz. Commonly used acids include sulfuric acid, hydrochloric acid, and hydrofluoric acid. However, although pickled quartz sand achieves a higher removal rate of impurities, improper treatment of the wastewater resulting from this process can have severe effects on the environment and soil. The pickling waste liquid contains large amounts of ions such as H+ and F-. If it is discharged directly without treatment, it can lead to serious consequences such as fluoride pollution, corrosion of underground pipelines, and contamination of groundwater. The following are several common treatment processes for quartz sand pickling waste liquid: (1) Neutralization + precipitation process. The quartz pickling waste liquid enters a regulation tank through drainage pipes, where its quality and volume are thoroughly adjusted. The wastewater after adjustment is then pumped to an acid-base reaction tank, where alkaline substances (such as caustic soda, sodium bicarbonate, lime, etc.) are added to carry out a neutralization reaction with the pickling waste liquid. Stirring is carried out while these substances are being added. After a period of time during which the acid and base react, the supernatant from the reaction tank overflows into a sedimentation tank. After sedimentation, the water quality is tested; if it meets the standards, the water can be discharged or reused. (2) Neutralization + precipitation + flocculation + pressure filtration for dewatering: The acid washing wastewater is directly discharged into a regulating tank, in which perforated aeration pipes are installed to homogenize and mix the wastewater. The wastewater is lifted from the regulating tank to the batch treatment tank by a lift pump for primary neutralization, thereby removing the majority of pollutants in the wastewater. The wastewater sludge after the neutralization reaction is allowed to settle in a batch treatment tank; the wastewater resulting from this settling process then undergoes a secondary coagulation reaction in the same tank, thereby completely removing pollutants from the wastewater and ensuring that it meets the required discharge standards. After the coagulation reaction, soluble pollutants are completely removed from the wastewater, and the sediment in the wastewater is trapped during the sand filtration process. (3) Neutralization + pressure filtration for dewatering + multi-stage filtration + reverse osmosis process: The silicic acid washing wastewater first enters a regulation and sedimentation tank, where lime water is added to adjust the pH to 8.5–9.5. After reacting for a period of time, a flocculant is added to aggregate the impurities and sludge in the water, thereby improving the solid-liquid separation process. The separated sludge is then sent to a sludge tank, where it is dehydrated using a plate and frame filter press before being transported away. The supernatant from the adjustment sedimentation tank is pumped up by a water pump, then passes through a quartz sand filter and an activated carbon filter, before entering a safety filter. After being pressurized by a high-pressure pump, it goes into the reverse osmosis membrane module; the concentrated water produced is sent back to the adjustment sedimentation tank, while the purified water enters a recycled water tank for reuse or discharge. (4) Haipu Special Adsorption Technology: Jiangsu Haipu Functional Materials Co., Ltd. is located in the Suzhou Industrial Park. It is a high-tech enterprise that focuses on special adsorbents and catalysts as its core technologies, and also provides services such as process development, technical support, and project implementation to help customers solve various environmental protection challenges. Heip’s technical team won the Suzhou Industrial Park Leading Talent Award in 2013 and 2015, as well as the Gusu Leading Talent Award in 2015. Jiangsu Heip Functional Materials Co., Ltd. was recognized as a **high-tech enterprise on two occasions, in 2015 and 2018; in 2018 it was designated as the Suzhou Engineering Technology Research Center for Adsorption and Catalytic Functional Nanomaterials. Jiangsu Haipu Functional Materials Co., Ltd. possesses advanced technical expertise in the treatment of adsorption materials; its accompanying adsorption treatment processes are efficient and stable, having helped numerous leading enterprises in various industries across China to overcome various environmental challenges. The basic principle of the treatment process using Heip’s special adsorption technology is to utilize the adsorption properties of special adsorbent materials to absorb and concentrate iron, calcium, and magnesium ions present in waste acid within these adsorbent materials. As a result, the concentration of acid ions is reduced, meeting the requirements of customers. After reaching adsorption saturation, the adsorbent material is desorbed to allow it to be regenerated and able to adsorb again, and this cycle repeats continuously. Process flow: As shown in Figure 1-1, the wastewater is first filtered to remove suspended solids and fine particles, thereby preventing impurities from entering the adsorption material and affecting its adsorption capacity. The filtered wastewater then enters an adsorption tower filled with special adsorbent materials for adsorption. Once saturated, the adsorbent materials are subjected to desorption and regeneration processes, after which they can be reused. The acid absorbed is recovered and reused by the customer, while the high-concentration desorbed liquid is handled by the customer. http://www.jshpfm.com/uploads/allimg/210517/1-21051F009463E.png file:///C:/Users/Jie/AppData/Local/Temp/ksohtml10736/wps17.png Figure 1-1 Process flow diagram. Scope of application: Acid washing wastewater from quartz sand ； Adsorption treatment cases: Our company conducted multiple batches of adsorption and desorption experiments on samples taken from a certain project site. The specific experimental results and comparison charts before and after treatment are as follows: Case 1 – Data on acid before and after adsorption. Parameters: Acid volume (m3/d), Iron (mg/L), Calcium (mg/L), Magnesium (mg/L). Acid before adsorption: 100, 241, 044, 531, 4; Acid after adsorption 1: 110, 008, 207, 410; Acid after adsorption 2: 110, 009, 02–4, 3–16; Acid after adsorption 3: 110, 009, 08–3, 4–16. http://www.jshpfm.com/uploads/allimg/210517/1-21051F01112300.png http://www.jshpfm.com/uploads/allimg/210517/1-21051F0112L96.png Figure 2-1: Principle of waste acid adsorption. Figure 2-2: Left side shows the original acid, right side shows the acid after adsorption. Advantages: 1. It solves the problem of managing industrial waste acid; the acid after adsorption can be reused, ensuring the sustainable development of enterprises and bringing significant economic and environmental benefits ； 2. Special adsorption materials feature high absorption capacity and high concentration ratios, resulting in low equipment investment and operating costs; 3. Automated control ensures easy operation and maintenance, as well as a long service life ； 4. The process flow is simple and reliable, with a small footprint.