Evaluation of sewage sludge ash performance in the retention of copper ions from wastewater using quality-by-design approach
摘要
The disposal of sewage sludge represents an important concern for the environment and its treatment is often expensive, since in most cases it requires the intervention of advanced treatment technologies. The reuse of sewage sludge for the production of adsorbent material for the removal of micropollutants from wastewater could therefore represent an attractive alternative. The aim of this work is to study the efficiency of a sewage sludge-based ash towards the removal of copper ions from wastewater. Specific surface area, pH of point of zero charge and scanning electron microscopy were used to characterize the produced adsorbent. In order to evaluate and to optimize the adsorption operating conditions of sewage sludge-based ash, Box–Behnken design method was established to highlight the influence of contact time, pH, mass of the adsorbent and copper initial concentration on the effectiveness of copper retention process. The use of the quality by design approach allowed us to identify the optimum conditions for the removal of copper by sewage sludge ash which are a contact time of 90 min, a pH value of 5, 1 g L−1 of adsorbent and a concentration of copper ions of about 15.75 mg L−1. Simulating these operating conditions, we were able to reach a copper removal efficiency of 80.73% and an adsorption capacity of 16.73 mg g−1. The ash from calcinated sewage sludge could therefore represent a high economic and environmental value.