Bayuseno Athanasius Priharyoto, Perwitasari Dyah Suci, Muryanto Stefanus, Tauviqirrahman Mohammad, Jamari Jamari
Department of Mechanical Engineering, Diponegoro University, Tembalang Campus, Semarang 50275, Indonesia.
Department of Chemical Engineering, Universitas Pembangunan National "Veteran" Jawa Timur, Surabaya 60294 Indonesia.
Heliyon. 2020 Mar 20;6(3):e03533. doi: 10.1016/j.heliyon.2020.e03533. eCollection 2020 Mar.
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. It was found that the crystallization rate constants range from 1.608 to 6.534 per hour, which agrees with the most published value. Higher maleic acid concentrations resulted in greater growth retardation; the highest retardation was 74.21%, which was achieved for 30 °C with 20.00 ppm maleic acid. SEM imaging of the obtained precipitates showed irregular prismatic morphology, and the associated EDX confirmed that the precipitates were struvite (MgNH PO ⋅6H O). As checked through XRD, the crystalline nature of the struvite was further confirmed, and that co-precipitation of struvite with struvite-K was observed. The co-precipitation was the result of K adsorption onto the crystal surface. Temperatures had less influence on struvite crystallization. At 40 C and 20.00 ppm the rate constant was 1.332 per hour; whereas at 30 C and 0.00 ppm) the corresponding was 1.776 per hour, indicating the retardation of about 25%. Thus, the temperature effect is only 1/3 of the maleic acid effect. The current findings suggest that the presence of maleic acid can be used to elucidate the mechanism of crystallization as well as the crystalline phase transformation of struvite. In practical terms, maleic acid could be potential as a scale inhibitor.
本研究报告了一项搅拌间歇式实验室结晶实验，以考察马来酸（HOOCCHCHCOOH）和温度（30和40°C）对鸟粪石结晶动力学和形态的影响。通过测量长达70分钟的pH变化来跟踪结晶过程。在实验开始的前5分钟，pH急剧下降，然后开始趋于平缓。结果发现，结晶速率常数范围为每小时1.608至6.534，这与大多数已发表的值相符。较高的马来酸浓度导致更大的生长抑制；最大抑制率为74.21%，这是在30°C、马来酸浓度为20.00 ppm时实现的。对所得沉淀物的扫描电子显微镜成像显示出不规则的棱柱形态，相关的能量散射X射线光谱证实沉淀物为鸟粪石（MgNH₄PO₄·6H₂O）。通过X射线衍射检查进一步证实了鸟粪石的晶体性质，并观察到鸟粪石与鸟粪石-K的共沉淀。这种共沉淀是K⁺吸附到晶体表面的结果。温度对鸟粪石结晶的影响较小。在40°C和20.00 ppm时，速率常数为每小时1.332；而在30°C和0.00 ppm时，相应的速率常数为每小时1.776，表明抑制率约为25%。因此，温度效应仅为马来酸效应的1/3。当前的研究结果表明，马来酸的存在可用于阐明鸟粪石的结晶机制以及晶相转变。实际上，马来酸可能具有作为阻垢剂的潜力。
