Alternative orange to dark red pigments were produced by purifying scum ashes from anaerobic treatment of domestic sewage. Scum samples collected a year apart were thermally treated at 650 °C/5 h to produce ashes, and these materials were purified to obtain intense colors, thermal stability, and reproducibility. Three different temperatures were used to calcinate the pigments. At 950 °C, the pigments achieved an intense orange color, which then became reddish and dark when the temperature was increased as a result of particle growth. All the samples presented the same crystalline phases, which is an important result that indicates reproducibility. These phases were identified by using Mössbauer spectroscopy, which revealed that the iron signature is mainly hematite (approximately 72%), and Fe²⁺ is probably related to the substitution of Ca²⁺ in the CaAl₉(PO₄)₇ phase. All the pigments presented good properties when used in ceramic enameling, but the samples produced at 1100 °C did not present a suitable size for application in polymer and paint. The samples produced at 950 and 1000 °C are more versatile and have many potential applications as an interesting alternative for the pigment industry and residue recycling, which is a problem in sewage treatment plants nowadays.

通过对生活污水进行厌氧处理来净化浮渣灰，从而生产出橙色至深红色的颜料。将每年收集的浮渣样品在650°C / 5 h进行热处理以生成灰烬，并对这些材料进行纯化以获得强烈的颜色，热稳定性和可重复性。使用三种不同的温度来煅烧颜料。在950°C时，颜料呈现强烈的橙色，当由于颗粒生长而使温度升高时，该颜料会变成红色和深色。所有样品均呈现相同的结晶相，这是表明可重复性的重要结果。这些相通过穆斯堡尔光谱法鉴定，表明铁的特征主要是赤铁矿（约72％）和Fe ²⁺可能与CaAl ₉（PO ₄）₇相中Ca ²⁺的取代有关。当用于陶瓷搪瓷时，所有颜料均表现出良好的性能，但是在1100°C下生产的样品没有呈现适合用于聚合物和油漆的尺寸。在950和1000°C下生产的样品用途更广泛，并有许多潜在的应用，可作为颜料工业和残留物回收的有趣替代品，这在当今的污水处理厂中是一个问题。