Recovery of High-Purity Magnesium Hydroxide with Self-Tuning PID Control and PID of pH

Document Type : Original Research Paper


1 Department of Environmental Engineering, Adiyaman University, P.O.Box 02040, Adiyaman, Turkey

2 Department of Chemical Engineering, Ankara University, P.O. Box 06100, Tandogan, Ankara, Turkey


The salt obtained from salt sources has a low purity level and contains contaminants. The primary contaminants in the brines were eliminated in this investigation by using analytical separation (titration) techniques. Following the purification method, sodium hydroxide (NaOH) was added to magnesium chloride (MgCl2) to make magnesium hydroxide (Mg(OH)2) coagulate in pH control. This was done by PID and Self-Tuning PID (STPID) Control. Using STPID Control, hydrochloric acid (HCl) at a rate of 20% was employed as an effective acid current, MgCl2 as a coagulant, and NaOH at a rate of 10% as a neutralization base throughout the process. The coagulation technique was carried out with pH values of 7, 9, and 11, respectively. The pH of the medium was adjusted using the PID and STPID algorithms, as well as an on-line computer control system. As the system model, ARMAX was employed. As a forcing function, a pseudo-random binary sequence (PRBS) was used to identify the dynamics of the process to be controlled, and the system output was measured. The Bierman algorithm was used to evaluate the model parameters. The STPID controller's tuning parameters were calculated. Following the coagulation method, an analytical titration procedure was used to find out if there are any trace amounts of Mg(OH)2 in the current environment, and a settlement percentage of 90% to 95% was found. To get the best coagulation, a pH value of 11 was chosen as the optimal value based on the performed calculations.


Alamdari, A., Rahimpour, M. R., Esfandiari, N. and Nourafkan, E. (2008). Kinetics of magnesium hydroxide precipitation from sea bittern. Chemical Engineering and Processing: Process Intensification, 47(2); 215–221. 
Alpbaz, M., Hapoglu, H., Ozkan, G. and Altuntas, S. (2006). Application of self-tuning PID control to a reactor of limestone slurry titrated with sulfuric acid. Chemical Engineering Journal, 116(1); 19–24. 
Altınten, A., Ketevanlioğlu, F., Erdoğan, S., Hapoğlu, H. and Alpbaz, M. (2008). Self-tuning PID control of jacketed batch polystyrene reactor using genetic algorithm. Chemical Engineering Journal, 138(1–3); 490–497. 
Bayram, İ. (2018). Removal of Major Impurties (Ca-Mg) of Brine with Chemical Treatment Process in the Salt Sector. International Scientific and Vocational Journal (ISVOS JOURNAL), 2(2); 57–66.
Bierman, G. J. (1975). Measurement Updating Using the U-D Factorization. Proceedings of the IEEE Conference on Decision and Control, 12; 337–346. 
Furqan AULIA. (2010). Self Tunıng PID Control of pH in Dye Wastewater Treatment by Usıng Coagulatıon Method. Ankara University.
Isdaryani, F., Feriyonika, F. and Ferdiansyah, R. (2020). Comparison of Ziegler-Nichols and Cohen Coon tuning method for magnetic levitation control system. Journal of Physics: Conference Series, 1450(1). 
La Corte, D., Vassallo, F., Cipollina, A., Turek, M., Tamburini, A. and Micale, G. (2020). A novel ionic exchange membrane crystallizer to recover magnesium hydroxide from seawater and industrial brines. Membranes, 10(11); 1–14. 
M. B. Zarrop, P. E. W. (1991). Self-tuning systems: Control and signal processing. Automatica Vol. 28. New York: VILEY. 
Mažuranıć, C., Bılınskı, H. and Matkovıć, B. (1982). Reaction Products in the System MgCl2‐NaOH‐H2O. Journal of the American Ceramic Society, 65(10); 523–526.
Newell R.B.; Lee, P. (1989). Applied Process Control-A case Study. Prentice Hall.
Seborg, D. E., Edgar, T. F. and Shah, S. L. (1986). Adaptive control strategies for process control: A survey. AIChE Journal, 32(6); 881–913.
Semerjian, L. and Ayoub, G. M. (2003). High-pH–magnesium coagulation–flocculation in wastewater treatment. Advances in Environmental Research, 7(2); 389–403.
Um, N. and Hirato, T. (2014). Precipitation behavior of Ca(OH)2, Mg(OH)2, and Mn(OH)2 from CaCl2, MgCl2, and MnCl2 in NaOH-H2O solutions and study of lithium recovery from seawater via two-stage precipitation process. Hydrometallurgy, 146; 142–148.