Influence of temperature and pH on phosphate removal efficiency of different sorbents used in lake restoration

Phosphorus sorbents (PS) are viewed as a powerful tool to manage eutrophication. Here, we tested three commercially available PS - lanthanum-modified bentonite (LMB), aluminium-modified zeolite (AMZ) and aluminium salts (Al) on their capacity to chemically inactivate soluble reactive phosphorus (SRP) at six different temperatures (5 to 35 degrees C) and five pH values (6 to 10). We also evaluated if the SRP bound at a neutral pH would be released if pH increases to pH 10. Results showed that temperature affected the SRP binding behavior differently for each PS. For instance, the highest SRP binding capacities of LMB, AMZ and Al were 14.0, 29.9 and 251.1 mg P g(-1) at 30 degrees C, 35 degrees C and 30 degrees C, respectively; and the lowest was at 35 degrees C for LMB, 25 degrees C for AMZ and 20 degrees C for Al (6.3, 4.0 and 205.2 mg P g(-1), respectively). The pH also affected the SRP binding differently. When pH increased from pH 6 to pH 10, LMB and Al decreased their binding capacity from 10.0 to 4.9 and from 571.7 mg P g(-1) to 21.3 mg P g(-1), respectively. The SRP adsorption capacity of AMZ was similar at pH 7 and 10 (6.3 and 6.2 mg P g(-1)). We observed that in high pH, LMB did not release the SRP precipitated. In contrast, AMZ and Al desorbed around 39%, and 71% of the SRP adsorbed when pH changed from 7 to 10. Abiotic factors such as pH should be considered when selecting the most promising material in lake restoration. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

This study tested three commercially available phosphorus sorbents (LMB, AMZ, and Al) on their capacity to chemically inactivate soluble reactive phosphorus (SRP) under different temperatures and pH values. The results showed that temperature and pH had different effects on the SRP binding behavior of each sorbent, indicating the importance of considering these factors in lake restoration.