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AbstractTo realize the safe disposal of solid waste containing heavy metals, sewage sludge jointly with slag and metakaolin was used to prepare alkali-activated materials (AAMs), and the effect mechanism of polycarboxylate acid superplasticizer (PCE), naphthalene superplasticizer (NS) and aliphatic superplasticizer (AS) in AAMs were studied. The results showed that both the fluidity and strength of AAMs decreased with the addition of sludge. For the NaOH + Na2SiO3 activated mortar specimen, the incorporation of sludge can reduce their fluidity and strength from 206 mm and 80.25 MPa to 193 mm and 42.43 MPa, respectively. However, the addition of superplasticizers into sludge-containing AAMs leads to a reduction of 3–9% of the fluidity. Interestingly, it can enhance the strength of the AAMs, especially the NS and AS, which increase the strength by approximately 25%. This is attributed to the increase of particle dispersion by superplasticizers. However, the free water released in the process is reabsorbed by the sludge, which increases the local alkali concentration and promotes the activation of the activity. The dispersed sludge particles can play the role of physical filling, making the structure denser. HIGHLIGHTSSludge is adverse effects on both the fluidity and strength of alkali-activated materials (AAMs).The addition of superplasticizers (SPs) increases the strength of AAM with sludge.SPs do not affect improving the fluidity of AAMs with sludge, even slightly bad.The dispersion effect of SPs on the sludge is beneficial to promote its activity in AAMs.Sludge is adverse effects on both the fluidity and strength of alkali-activated materials (AAMs).The addition of superplasticizers (SPs) increases the strength of AAM with sludge.SPs do not affect improving the fluidity of AAMs with sludge, even slightly bad.The dispersion effect of SPs on the sludge is beneficial to promote its activity in AAMs. [ABSTRACT FROM AUTHOR]

MnO x /sewage sludge-derived activated carbon (MnO x /SAC) was prepared as catalysts to improve the performance of aqueous oxalic acid degradation by ozonation. The results indicated that MnO x /SAC had excellent catalytic activity in mineralization of oxalic acid during heterogeneous catalytic ozonation process. MnO x /SAC with a manganese load of 30% exhibited the strongest catalytic activity under the condition of solution pH 3.5, which enhanced the oxalic acid removal from 10.3% to 92.2% in 60 min compared with that treated by ozone alone. Increase of catalyst dosage and aqueous ozone concentration was advantageous for oxalic acid removal from water. On the basis of catalyst characterization analysis and the observation of inhibitory effect induced by higher pH, less catalyst dosage as well as the presence of hydroxyl radical scavenger, it was deduced that the reaction mechanism involved both hydroxyl radicals attack and surface reactions. [ABSTRACT FROM AUTHOR]