Julia Uy The negative percent removal of chromium when using hydroxyapatite for adsorption can occur due to various factors such as experimental errors, saturation of the adsorbent, or the presence of competing ions affecting the adsorption process. In the study mentioned, the adsorption of chromium using hydroxyapatite at different dosages (0.2, 0.6, and 1 g) from a 2 ppm solution resulted in negative percent removal, which could be attributed to experimental limitations or complexities in the adsorption process. You will have to identify, which are the controlling factors.
The negative percent removal could also be due to errors in the experimental setup, calculation, or analysis. It is essential to ensure the accuracy of measurements, dosages, and calculations to avoid such discrepancies. Additionally, the saturation of the adsorbent at higher dosages could lead to reduced efficiency and even negative removal values.
Moreover, the presence of competing ions in the solution, as mentioned in the study, can interfere with the adsorption of chromium onto hydroxyapatite, affecting the overall removal efficiency. Competing ions like Fe3+, Al3+, Zn2+, and Mn2+ can compete for adsorption sites on the adsorbent, impacting the effectiveness of chromium removal. Also identify the ionic interference, due to this chromium starts getting back into the solution.
In conclusion, the negative percent removal of chromium when using hydroxyapatite for adsorption from a 2 ppm solution could be due to experimental errors, saturation of the adsorbent, or the presence of competing ions affecting the adsorption process. Further investigation and optimization of experimental conditions are necessary to understand and improve the adsorption efficiency in such scenarios.
Kindly refer the articles mentioned as below, maybe these would be somewhat useful
[1] https://www.sciencedirect.com/science/article/abs/pii/S2214785321064877
[2] https://www.nature.com/articles/s41598-023-44852-7
[3] https://pubmed.ncbi.nlm.nih.gov/22888714/
[4] https://nopr.niscpr.res.in/bitstream/123456789/60323/1/IJMS%2051(5)%20459-467.pdf.pdf
[5] https://www.sciencedirect.com/science/article/abs/pii/S0169131719300584