Polyaluminium Chloride (PAC) as a Highly Efficient Inorganic Coagulant: An Update of Its Cost-Effective Manufacturing Process-A Review

Background: Growing global water pollution and the need for sustainable treatment technologies have intensified the demand for high-performance coagulants like PAC. Consequently, research has focused on developing economically viable and environmentally friendly manufacturing approaches without compromising its efficiency. Aims: Polyaluminium chloride (PAC) has emerged to be the most effective coagulant for water treatment over most conventional coagulants because of its low dosage amounts required, less flocculation time, less sludge, high efficiency and less aluminium residues remain in treated water. The current commercial preparation method involves the use of rigorous conditions and expensive raw materials which drives high production cost such that its adoption by low-income economies is hindered. Over the years various studies have been devoted to find cost effective methods of producing PAC. Thus, the present review aims at providing a systematic review of such methods. Study Design: Systematic review of literature. Place and Duration of Study: Harare Institute of technology Jan-March 2026. Methodology: Data collection was performed by searching major databases, Scopus, Google scholar, Scifinder and Springer up to March 2026 with the key phrases cost-effective or low-cost methods of preparing PAC. The inclusion criteria involved only scientific studies reporting cost-effective methods while the exclusion criteria involved rejecting all studies describing high-cost PAC synthesis methods and those reporting vigorous conditions Results: A total of 338 publications were systematically screened. Relevant records from Google scholar were 150, Science Direct 100, Scopus 66 and SciFinder 22. On analysis the final selection consisted of 17 (5%) primary publications reporting cost effective manufacturing procedures, and 5 (29%) with real industrial applications. From the greened studies, there is a general agreement that in order to bring down the cost, methods that utilizes locally available, affordable, sustainable and promote ecofriendly efforts and allows the use of mild preparation conditions should be adopted. Natural, industrial, mining and home waste residues have been selected for use as raw materials in PAC preparations. Among the raw materials selected bauxite, kaolin and aluminium tins and scrapings have been widely studied and they produced PAC that was pure, highly efficient and of desirable basicity. Its performance was not inferior to PAC produced by the standard industrial preparation method. Calcination and electrochemical methods have been reported to be cost effective methods that do not depend on the use of vigorous conditions. Thus, PAC produced using these alternative procedures was said to be also useful not only in the treatment of waste water but also in treating drinking water. Conclusion: Although the PAC produced by alternative methods was extensively checked for quality in terms of purity (Al/OH) ratio, contamination and other important parameters, few studies went further to utilize it to treat real environmental water and check the feasibility in terms of process cost and efficiency in its application in a real industrial set up. This gap require interrogation so that the studies can be complete and useful.