I. Major Pollutants in Silica Production
1. Wastewater Composition and Characteristics
Wastewater generated during silica production primarily consists of the following components:
High-concentration silica particles: Primarily from cooling water and wash water during production
Petroleum-based substances and chemical additives: Including various chemical additives used in the production process
Organic matter: Primarily from organic pollutants in wash water
Particulate matter: Wastewater contains a certain concentration of solid particulate matter

2. Waste Gas Composition and Characteristics
The waste gas from precipitated silica production can be divided into two main categories: particulate matter and gaseous pollutants:
Particulate Matter: Incompletely collected carbon black dust, typically with a particle size between 10 nanometers and 500 nanometers, possessing extremely strong adsorption and dispersibility.

Gaseous Pollutants:
Carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2), nitrogen oxides (NOx)
Volatile organic compounds (VOCs)
Polycyclic aromatic hydrocarbons such as benzo[a]pyrene (highly carcinogenic)
Potentially generated by gas-phase production: silicon tetrachloride (SiCl₄), hydrogen (H₂), and hydrogen chloride (HCl)

II. precipitated silica wastewater treatment technology
1. Main Treatment Processes
Electrolytic Desiliconization: The wastewater to be treated is cooled and then subjected to electrolytic desiliconization.
Ultrafiltration: The wastewater after electrolytic desiliconization is subjected to ultrafiltration.
Reverse Osmosis: The ultrafiltration water is subjected to reverse osmosis to produce a first product water and a first concentrate.

Nanofiltration: The first concentrate is subjected to nanofiltration to produce a second product water and a second concentrate.
Evaporation: The second product water is evaporated to produce sodium bicarbonate, and the second concentrate is evaporated to produce sodium carbonate.

2. Characteristics of Treatment Technology
The combined process can achieve "zero" discharge of wastewater from the carbonization process of precipitated silica.
It greatly reduces the treatment cost of wastewater from the carbonization process of precipitated silica.
Using appropriate wastewater treatment technology can reduce the impact on the environment.

III. precipitated silica waste gas treatment technology
1. Dust Control Technology
Cyclone Dust Collector + Bag Filter Combined Process:
Primary Treatment: Utilizes a CLK-type diffusion cyclone dust collector, handling coarse particles >10μm in diameter, with a dust removal efficiency of approximately 85%.
Secondary Treatment: Equipped with an anti-static membrane-coated bag filter, controlling the filtration velocity below 0.8m/min, with an outlet concentration <10mg/m³.

Wet Electrostatic Precipitator Process:
Suitable for high humidity (>60%RH) conditions.
Uses lead-antimony alloy barbed wire with fiberglass anode tubes.
The spray system uses a 0.5% NaOH solution to neutralize acidic components.

2. Gaseous Pollutant Treatment
Spray Tower Treatment: Dust-laden gas enters the spray tower and comes into uniform contact with circulating water.
Dust combines with water and settles in the wastewater tank, while clean gas is discharged.
Explosion-proof Design: Pipeline grounding and flange bridging prevent static electricity accumulation.

3. Dust Resource Utilization
After vibratory screening, qualified products (particle size <45μm) are returned to the production process. Agglomerated materials are sent to a calciner at 800°C for regeneration. Impurities (e.g., Fe₂O₃ > 0.3%) are used as building materials.

IV. Advanced Environmental Protection Processes and Standards
1. Environmentally Friendly Production Processes
Graphene-Based Method: Leveraging the unique structure and excellent properties of graphene, silica is produced through high-temperature catalytic cracking of graphene materials, offering high efficiency and environmental protection.

Incineration Method: A high-temperature redox method, utilizing controlled high-temperature calcination under different atmospheres to induce redox reactions in carbon-containing materials to produce silica.
Rice Husk Ash to Silica: Carbonization and activation of rice husk ash produce silica, achieving waste resource utilization.

2. Environmental Protection Standards
GB/T Standard 37798-2019, *Technical Requirements for Silica Industry*, clarifies the definition and classification of silica. It specifies technical requirements for color, specific surface area, ink adsorption value, pH value, and residue on ignition. It details test methods, inspection rules, and marking requirements.

V. Typical Case Studies
1. Silica Dust Treatment Project at a Silicone Factory in Dongguan
Treatment Process: Pulse bag filter + optimized feeding method
Treatment Effect: Dust concentration reduced to ≤12mg/m³, recovered dust can be reused in production.

2. Dust Treatment Project at Purson Plastics Technology (Shenzhen) Co., Ltd.
Treatment Process: Spray tower treatment + explosion-proof design
Treatment Effect: Emission dust concentration ≤8mg/m³, significantly reducing the risk of dust explosion in the workshop.

3. Conveying Dust Control at a Silica Production Line in Shanghai
Treatment Process: Tubular chain conveyor system modification + closed collection
Treatment Effect: Dust leakage in the conveying process reduced by more than 95%.