Calcination-based direct extraction of hydroxyapatite from bovine bone waste.

The main chemical components of waste cow bones are apatite minerals, especially those containing calcium and phosphorus. This study investigated whether this bone could produce extracted hydroxyapatite through calcining at 900° C for different holding times (1-6 h). An average mass loss of 45% occurred in this experiment during the preparation of bone powders, which involved crushing and further calcining at this temperature.

In-depth knowledge of the low-temperature hydrothermal synthesis of nanocrystalline hydroxyapatite from waste green mussel shell ().

This study presents the use of a low-temperature hydrothermal method for extracting calcium sources from green mussel shell () wastes and converting them into synthetic nanosized hydroxyapatite (HA). In this study, raw mussel shells were washed, pulverised, and sieved to start producing a fine calcium carbonate-rich powder. XRD quantitative analysis confirmed that the powder contains 97.

Practical insights into the recycling of green mussel shells () for the production of precipitated calcium carbonate.

The study presented a powder processing method involving calcination and subsequent carbonation in the synthesis of precipitated calcium carbonate (PCC) for recycling green mussel shells, which contain a high calcium carbonate content. The purity of portlandite [Ca(OH)] as a result of calcination and subsequent moisture absorption during storage was verified using the XRD-Rietveld method. Further quantitative XRD Rietveld analysis of the PCC product confirmed the presence of vaterite (55.

Evaluation on the automotive skill competency test through 'discontinuity' model and the competency test management of vocational education school in Central Java, Indonesia.

This article provides an alternative competency test model for vocational education schools in Central Java, Indonesia which particularly for automotive skill competency in order to replace the current competency test model that has been implemented for several decades which the author's concern about the students' accomplishment during the competency test, aimed to improve competency test results to increase the students' job opportunity in the labor market. Currently, the applied competency test model is the 'Continuity' model, where the students are given five tasks and should be finished within five hours with limited break time. This model tends to increase students' fatigue and stress levels.

Kinetics and morphological characteristics of struvite (MgNHPO.6HO) under the influence of maleic acid.

This work reports a stirred-batch lab crystallization to examine the influence of maleic acid (HO CCHCHCO H), and temperatures (30 and 40 °C) on crystallization kinetics and morphology of struvite. The crystallization was followed by measuring the pH change up to 70 min. The pH decreased drastically for the first 5 min of the run, then started to tail off.