Rod milling sand(RMS)—a coarse sand aggregate—was recycled for cemented paste backfill(CPB)for the underground mined area at the Jinchuan nickel deposit,named rod milling sand-based cemented paste backfill(RCPB).The...Rod milling sand(RMS)—a coarse sand aggregate—was recycled for cemented paste backfill(CPB)for the underground mined area at the Jinchuan nickel deposit,named rod milling sand-based cemented paste backfill(RCPB).The adverse effects of coarse particles on the transportation of CPB slurry through pipelines to underground stopes resulting in weakening of the stability of the backfill system are well known.Therefore,sulfonated naphthalene formaldehyde(SNF)condensate was used for the performance improvement of RCPB.The synergistic effect of solid content(SC),lime-to-sand ratio,and SNF dosage on the rheological and physicomechanical properties,including slump,yield stress,bleeding rate,uniaxial compressive strength(UCS),as well as mechanism analysis of RCPB,have been explored.The results indicate that the effect of SNF on RCPB performance is related to the SNF dosage,lime-to-sand ratio,and SC.The slump of fresh RCPB with 0.1wt%-0.5wt%SNF increased by 2.6%-26.2%,whereas the yield stress reduced by 4.1%-50.3%,indicating better workability and improved cohesiveness of the mix.The bleeding rate of fresh RCPB decreased first and then rose with the increase of SNF dosage,and the peak decrease was 67.67%.UCS of RCPB first increased and then decreased with the increase of SNF dosage.At the optimal SNF addition ratio of 0.3wt%,the UCS of RCPB curing for 7,14 and,28 d ages increased by 31.5%,28.4%,and 29.5%,respectively.The beneficial effects of SNF in enhancing the early UCS of RCPB have been corroborated.However,the later UCS increases at a slower rate.The research findings may guide the design and preparation of RCPB with adequate performance for practical applications.展开更多
β-naphthalene sulfonic acid sodium-formaldehyde condensate is an important additive as dispersant,water reducing agent,surfactant and antioxidant in electrolytic metal manganese process.The free formaldehyde in the c...β-naphthalene sulfonic acid sodium-formaldehyde condensate is an important additive as dispersant,water reducing agent,surfactant and antioxidant in electrolytic metal manganese process.The free formaldehyde in the condensate inevitably affects its performance.The content of free formaldehyde can be determined with HPLC method by previously reacting with 2,4-dinitrophenylhydrazine to derive 2,4-dinitrophenylhydrazone.This paper optimized the reaction condition for formaldehyde derivative formation,2,4-dinitrophenylhydrazone is totally transformed form formaldehyde in 20 min,at 30℃,in hydrochloric acid.For the external standard method,the correlation coefficient(r) and RSD were 0.9999,4.07%,respectively,and the detection limit was 0.1mg/L.To spike the samples with formaldehyde at concentration of 1.25,2.50,and 7.50 mg/L,the recoveries were 98.4%,94.0% and 97.0%,respectively.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52104156,52074351,52004330)the Science and Technology Innovation Program of Hunan Province,China(No.2021RC3125)the Natural Science Foundation of Hunan Province,China(No.2022JJ30714)。
文摘Rod milling sand(RMS)—a coarse sand aggregate—was recycled for cemented paste backfill(CPB)for the underground mined area at the Jinchuan nickel deposit,named rod milling sand-based cemented paste backfill(RCPB).The adverse effects of coarse particles on the transportation of CPB slurry through pipelines to underground stopes resulting in weakening of the stability of the backfill system are well known.Therefore,sulfonated naphthalene formaldehyde(SNF)condensate was used for the performance improvement of RCPB.The synergistic effect of solid content(SC),lime-to-sand ratio,and SNF dosage on the rheological and physicomechanical properties,including slump,yield stress,bleeding rate,uniaxial compressive strength(UCS),as well as mechanism analysis of RCPB,have been explored.The results indicate that the effect of SNF on RCPB performance is related to the SNF dosage,lime-to-sand ratio,and SC.The slump of fresh RCPB with 0.1wt%-0.5wt%SNF increased by 2.6%-26.2%,whereas the yield stress reduced by 4.1%-50.3%,indicating better workability and improved cohesiveness of the mix.The bleeding rate of fresh RCPB decreased first and then rose with the increase of SNF dosage,and the peak decrease was 67.67%.UCS of RCPB first increased and then decreased with the increase of SNF dosage.At the optimal SNF addition ratio of 0.3wt%,the UCS of RCPB curing for 7,14 and,28 d ages increased by 31.5%,28.4%,and 29.5%,respectively.The beneficial effects of SNF in enhancing the early UCS of RCPB have been corroborated.However,the later UCS increases at a slower rate.The research findings may guide the design and preparation of RCPB with adequate performance for practical applications.
文摘β-naphthalene sulfonic acid sodium-formaldehyde condensate is an important additive as dispersant,water reducing agent,surfactant and antioxidant in electrolytic metal manganese process.The free formaldehyde in the condensate inevitably affects its performance.The content of free formaldehyde can be determined with HPLC method by previously reacting with 2,4-dinitrophenylhydrazine to derive 2,4-dinitrophenylhydrazone.This paper optimized the reaction condition for formaldehyde derivative formation,2,4-dinitrophenylhydrazone is totally transformed form formaldehyde in 20 min,at 30℃,in hydrochloric acid.For the external standard method,the correlation coefficient(r) and RSD were 0.9999,4.07%,respectively,and the detection limit was 0.1mg/L.To spike the samples with formaldehyde at concentration of 1.25,2.50,and 7.50 mg/L,the recoveries were 98.4%,94.0% and 97.0%,respectively.
