Adsorption Application of Walnut Shell Filter Material to Lead Ion in Industrial Wastewater

Frequent industrial activities have led to increasingly prominent environmental pollution and ecological problems. Heavy metals are a more harmful pollutant and are non-degradable. Because of its high toxicity, it will cause serious pollution to the environment even at lower concentrations. Lead ions in the environment mainly come from battery production workshops and petrochemical plants, especially battery plants will produce a large amount of lead-containing wastewater during the production process. The content of lead ions in the wastewater exceeds the national standard by hundreds of times. If it is not treated, it is arbitrary Emissions will inevitably bring great harm to the environment and society.
      At present, the methods for treating wastewater containing lead ions include chemical precipitation, ion exchange, membrane separation, and adsorption. Chemical precipitation method is one of the most widely used methods. The method is simple and easy to operate, but it has poor treatment effect on low-concentration wastewater and easily produces a large amount of sludge. The ion exchange method has high selectivity and can remove a variety of heavy metals. The price of exchange resin is high, and the operating cost is also high; the biosorption method can use cheap biological materials to adsorb heavy metals, especially for low-concentration wastewater treatment. Walnut shells are agricultural and forestry wastes, with large yields, low costs, and stable properties.
      The adsorption of lead ions in industrial wastewater by walnut shells is mainly affected by the particle size and addition amount of walnut shell adsorbent, initial wastewater Ph, and adsorption time. After a large number of experiments, it is shown that when the initial lead ion mass concentration is 20mg/L, the initial wastewater Ph=5.5, the amount of adsorbent added is 12g/L, the adsorbent particle size is 1.60-2.50mm, and the adsorption time is 120min, the homemade walnut shell adsorbent is effective for lead The removal rate of ions is 91.7%. The mass concentration of lead ions in the wastewater after adsorption is less than 1.0 mg/L, which meets the requirements specified in GB8978-1996 "Integrated Wastewater Discharge Standard".