Vol. 12 | No. 2 |787 – 795| April - June | 2019 ISSN: 0974-1496 | e-ISSN: 0976-0083 | CODEN: RJCABP http://www.rasayanjournal.com http://www.rasayanjournal.co.in Rasayan J. Chem., 12(2), 787-795(2019) http://dx.doi.org/10.31788/RJC.2019.1225125 OPTIMIZATION OF KEY PARAMETERS IN STRUVITE (K) PRODUCTION FOR PHOSPHORUS AND POTASSIUM RECOVERY USING A BATCH CRYSTALLIZER D. S. Perwitasari 1 , S. Muryanto 2 , M. Tauviqirrahman 3 , J.Jamari 3 , and A.P. Bayuseno 3,* 1 Department of Chemical Engineering, Universitas Pembangunan National “Veteran” Jawa Timur, Surabaya, Indonesia 2 Department of Chemical Engineering, UNTAG University in Semarang, Indonesia 3 Department of Mechanical Engineering, Diponegoro University, Tembalang Campus, Semarang, Indonesia *E-mail:apbayuseno@gmail.com ABSTRACT Struvite (K) precipitation can be used for recovering the valuable nutrients, mainly phosphorus (P) and potassium (K) from wastewater. In this study, the key parameters controlling its precipitation in a batch crystallizer, namely temperature (30-40 O C), stirring rate (200-400 rpm), citric acid concentration (1-20 ppm) were optimized using SRM (surface response methodology) for yielding the optimum mass of the struvite (K) crystal. The XRPD Rietveld method confirmed that struvite (K) and impurity of sylvite (KCl) were precipitated from the pH solution of 9. The most significant factor corresponding to the yield response was predicted by SRM to be temperature, while the stirring rate and the citric acid concentration are insignificant factors contributing to the optimal mass yields. The optimum mass of precipitates (14.682 mg) was obtained, when the precipitation process was set at the temperature of 39 O C, a stirring rate of 376 rpm and citric acid concentration of 2.2350 ppm. These parameters would be the best design factors for yielding the optimum struvite (K) crystal with the purity of more than 99 wt. %. Keywords: P and K-recovery, Struvite (K), Surface Response Methodology (SRM), Citric Acid, XRPD Rietveld Analysis © RASĀYAN. All rights reserved INTRODUCTION Magnesium ammonium phosphate (MAP) could precipitate from an aqueous solution leading to the scale deposition of struvite (MgNH4PO4 6H2O) minerals, which have detrimental effects of the process on pipes, pumps, tanks, and other industrial equipment 1, 2 . This formation of hard scale can hinder a stream flow, which in turn requires the periodic cleaning of pipelines. However, the use of chemical agents (e.g., KOH and MgCl2) in the wastewater may provide the benefit of MAP precipitation, which can recover potassium, phosphate, and ammonia to prevent eutrophication in an efficient way 1,3-5 . Additionally, the use of crystallization technology may recover valuable nutrients contained in wastewater through the precipitation of struvite and/or struvite (K) (KMgPO4 6H2O) with improved morphology and homogeneous particle size 6 . More recently, the MAP crystallization offers an efficient way of phosphate recovery from the wastewater at high energy efficiency and productivity of solids manufacturing 5, 7 . This method has been widely applied for phosphate removal from calf manure, and different wastewater 8, 9 . The MAP with the molar ratio of 1:1:1 can crystallize in the form of struvite according to the reaction below (1) 1 : (1)