Abstract The pyrolytic conversion of sewage sludge to char is a promising way for its utilization. To explore their effects, inorganic salts containing Ca, Al, chlorine, sulfate and phosphate were added into sewage sludge prior to pyrolysis at 500 °C. The ash content, yield and pH changed depending on salt species. Salt-addition catalyzed the decomposition of organic matters and decreased the contents of C, H, N and S. Some of the intrinsic minerals were lost or converted while new minerals were formed involving the added and intrinsic ions. The retention of Cu, Mn, Zn and Pb was reduced at the presence of excessive chlorine. Sulfate moderately promoted volatilization, while phosphate offset the effect of chlorine. Chlorine transformed residual fraction of Pb to exchangeable fraction, while sulfate inhibited the transformation of heavy metals from mobile to immobile fractions. Phosphate increased the residual fraction. The mechanisms included direct reactions between the added anions and heavy metals, and altered affinity between heavy metals and the organic and mineral components. The presence of inorganic salts affects char characteristics and heavy metal risks, which should be considered in char production and application.

中文翻译：

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添加盐分对污水污泥炭特性和重金属行为的影响

摘要 污水污泥热解制炭是一种很有前景的利用方式。为了探索它们的影响，在 500 °C 热解之前，将含有 Ca、Al、氯、硫酸盐和磷酸盐的无机盐添加到污水污泥中。灰分含量、产量和 pH 值随盐的种类而变化。加盐催化有机物分解，降低C、H、N、S的含量。一些固有矿物丢失或转化，而新矿物在加入和固有离子的作用下形成。在过量氯的存在下，Cu、Mn、Zn 和 Pb 的保留减少。硫酸盐适度促进挥发，而磷酸盐抵消氯的影响。氯将 Pb 的残留部分转化为可交换部分，而硫酸盐则抑制重金属从移动部分向固定部分的转化。磷酸盐增加了残留分数。这些机制包括添加的阴离子与重金属之间的直接反应，以及改变重金属与有机和矿物成分之间的亲和力。无机盐的存在会影响焦炭特性和重金属风险，在焦炭生产和应用中应予以考虑。