Tofu Factory Liquid Waste for Making Struvite with Canted Vertical Reactors

Sutiyono Sutiyono,Kartika Pratiwi,Achmad Fanani,Luluk Edahwati Luluk Edahwati

doi:10.33005/ijeise.v1i01.9

Abstract

Struvite is a white crystal, chemically known as magnesium ammonium phosphate hexahydrate (MgNH4PO4.6H2O). Tofu factory liquid waste is waste that can be reused because of its content. Tofu factory liquid waste can potentially pollute the environment. This research aimsto analyze the manufacture of struvite by utilizing the phosphate content contained in the liquid waste of tofu factories using vertical canted column reactors which can reduce environmental pollution due to liquid waste of tofu factories. This study uses a vertical canted column reactors by mixing anequimolar 1: 1: 1 MgCl2: NH4OH: H3PO4 solution. Struvite crystallization process operates at a temperature variation of 30°C,35°C,40°C,45.50°Cand a pH of 8, 9,10,11,12 by maintaining the air rate of 0.5 liters minute-1 and a MAP (Magnesium Ammonium Phosphate)flow of 56 ml minutes-1 as a whole. The crystallization process runs until a steady state conditionis reached. Then, the struvite crystals obtained were filtered and dried at room temperature for 24 hours. After that struvite crystals were analyzed using XRF, XRD, and SEM. The results of the study obtained the best phosphate conversion of 24.935% at 30°C and pH 8.

Highlights

The formation of the crystal core can be formed when the concentrations of magnesium, ammonium, and phosphate exceed the solubility of the resulting product which is expressed by the Ksp value
That is because at pH above 10 will tend to form Mg (OH)2, thereby reducing the availability of Mg ions which can reduce the productivity of struvite crystal formation [3]
Characteristics of Struvite Crystal Products Scanning Electron Microscope (SEM) in an electron microscope that draws the surface of the specimen by scanning using high-energy electron rays in scans and raster patterns that attains the sizes detail less than 1 nm [4]

Summary

Introduction

Tofu factory waste consistsof two types, namely solid waste and liquid waste. Tofu factory solid waste is obtained from the washing process and by products in the process of making tofu that is solid and obtained from squeezed soybean pulp. While the liquid waste of the tofu factory is obtained from the process of soaking, washing soybeans, washing the process of tofu production equipment, filtering and pressing or making tofu. Tofu factory liquid waste has a variety of organic materials and found gases such as (O2), hydrogen sulfide (H2S), ammonia (NH3), carbon dioxide (CO2), and methane (CH4) [1]. Tofu factory liquid waste contains nutrients, namely N 1.24%; P2O5 5.54%; K2O. Struvite is a crystal containing magnesium, ammonium, and phosphate. Struvite formation reaction: teeth along the arch. The second reinforcing rod is patented at the end of the ellipse at an angle of 30° and the third at the junction of the serrations with the first support, with an angle of approximately 70 ° [7]

Material and Method

Results and Discussion

The Effect of Temperature on Percent Phosphate Conversion

Conclusions