Citation: Harharah, R.H.; Abdalla, G.M.T.; Elkhaleefa, A.; Shigidi, I.; Harharah, H.N. A Study of Copper (II) Ions Removal by Reverse Osmosis under Various Operating Conditions. Separations 2022, 9, 155. https://doi.org/10.3390/ separations9060155 Academic Editor: Mingheng Li Received: 30 May 2022 Accepted: 17 June 2022 Published: 20 June 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). separations Article A Study of Copper (II) Ions Removal by Reverse Osmosis under Various Operating Conditions Ramzi H. Harharah 1, * , Ghassan M. T. Abdalla 2 , Abubakr Elkhaleefa 1 , Ihab Shigidi 1 and Hamed N. Harharah 1 1 Department of Chemical Engineering, College of Engineering, King Khalid University, Abha 61421, Saudi Arabia; amelkhalee@kku.edu.sa (A.E.); etaha@kku.edu.sa (I.S.); hhharharah@kku.edu.sa (H.N.H.) 2 Department of Electrical and Electronic Engineering, Faculty of Engineering, University of Khartoum, Khartoum P.O. Box 10179, Sudan; gmtshigidi@gmail.com * Correspondence: r.binharharah@kku.edu.sa Abstract: The study aims to treat artificial wastewater contaminated with copper (II) ions by reverse osmosis using (SEPA CF042 Membrane Test Skid-TFC BW30XFR). Several concentrations of feedstock were prepared. Different operating pressure, temperature, and flow rate were applied. The effect of these operating conditions on both the amount of Cu (II) removal and the permeate flux was monitored. The results of the study revealed that both the permeate flux and Cu (II) removal amount were directly proportional to the operating pressure and feed temperature but inversely proportional to the feed concentration. In contrast, the feed flow rate showed a negligible effect on the permeate flux and Cu (II) removal amount. The temperature correction factor (TCF) of the membrane was calculated and was found to be directly proportional to the feed temperature but inversely proportional to the applied pressure. It was seen that the concentration and flow rate of that feed did not affect the temperature correction factor. Mathematical models have been developed based on these experimental data for both permeate flux and the Cu (II) removal. It was noted that the permeate flux model matched the experimental data, while the Cu (II) removal model did not show a perfect match. In addition to the above, the research highlights for subsequent studies the possibility of a deep link between experimental work and mathematical models. Keywords: reverse osmosis performance; artificial wastewater; copper (II) removal; temperature correction factor; mathematical models 1. Introduction Nowadays, as a result of growing industrialization and urbanization, water is becom- ing increasingly polluted, where large quantities of contaminants are being released into the environment as a result of physical, chemical, and biological processes. Heavy metals are amongst the most harmful pollutants due to their non-degradable properties. They are toxic and carcinogenic agents that accumulate over time and cause problems to human health and the ecosystem [1]. Copper is one of these heavy metals. It has an atomic weight of 63.5 g/moL and a den- sity of 8.96 g/cm 3 . It is present in a range of physical and chemical forms in ecosystems, and some are discharged from industrial processes and then accumulate in the environment [2]. Copper (II) in wastewater is discharged from many industries such as the electroplating industry, plastic industry, metal refining and industrial emissions [1]. Long-term exposure to copper irritates the nose, mouth, eyes, headache, stomachache, dizziness and diarrhea. The maximum contamination level (MCLs) of Cu (II) that has been set by the World Health Organization (WHO) is 2 mg/L [3]. Heavy metals such as copper should be eliminated from industrial wastewater before reaching the natural environment, and this can be accomplished through various treatment Separations 2022, 9, 155. https://doi.org/10.3390/separations9060155 https://www.mdpi.com/journal/separations