Effect of particle size of hydroxyapatite based coral as absorbant of nickel contaminant

Synthesis of coral-based hydroxyapatite has been carried out by the precipitation method. From diffraction x-ray spectrum data, using of precipitation method on coral can produce calcium phosphate compounds of hydroxyapatite type of 95.1%, and its residue is tricalcium phosphate (TCP). The formation of variations in hydroxyapatite particle size is milling using high energy milling (HEM-3D) at different times. In this study, the duration of milling was carried out for 5, 10, 15, 20 and 25 hours respectively which resulted in particle sizes of 2411 nm, 774.3 nm, 541.5 nm, 252 nm, and 143.4 nm. Hydroxyapatite particle size distribution with 28 hours milling time formed 2 peaks at 11.7 nm with an intensity of 55.8% and 458.7 nm with an intensity of 44.2%. Hydroxyapatite samples with different particle sizes are used to absorb nickel in a simulated solution of nickel waste. The ICP test results showed that the smaller particle size produces the greater percent removal of nickel by hydroxyapatite adsorbents, making it more effective as an adsorbent for nickel heavy metals. The biggest percentage of nickel removal is 99.913% which occurs at a particle size of 11.7 nm.