Department of Civil Engineering

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Subject: search.filters.subject.Hazardous waste

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    Synergic valorization of nickel-chrome plating sludge via alkali activation of steel slag and fly ash: performance analysis
    (Springer, 2024-09) Lahoti, Mukund; Singhal, Anupam; Routroy, Srikanta; Bhunia, Dipendu
    Nickel–chromium plating sludge (NCPS) is a hazardous waste due to high concentration (~ 25%–30%) of chromium and nickel. Electric arc furnace slag (EAFS) is a by-product of secondary steel manufacturing through the electric arc furnace route. In this work, we valorized NCPS in an innovative ambiently cured alkali-activated NCPS-Fly ash-EAFS mortar (ANFEM). NCPS substituted the binder from 0 to 25% (by weight) in the step size of 5%. The binder composition had EAFS/fly-ash = 1.0, activator/binder = 0.45, silicate/hydroxide = 2.5. Incorporation of NCPS in ANFEM resulted in several benefits such as successful NCPS immobilization, improving the flash setting and flowability issues of alkali-activated EAFS and minimal degradation in mechanical properties. Microstructural investigation by XRD, FTIR, SEM offered insights on the underlying mechanisms of NCPS valorization and corroborated the observed results of compressive strength, water absorption, bulk density, acid resistance, and surface porosity test. At 10 wt% substitution of NCPS, ANFEM produced optimum results, such as compressive strength of 40 MPa; Wabs enhancement by 4.2%; bulk density reduction by 1.1%; and the least acid-induced deterioration. Extensive leaching tests determined leachate’s heavy metals concentration to be well-within the permissible limits. Factory scale deployment of developed methodology produced paver blocks well-satisfying Indian Standard Code 15,658: 2006.
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    A Study on Utilization of Treated Spent Liquor Sludge with Fly Ash by Making Cement Concrete Hollow Cavity Bricks
    (World Academic Publishing, 2012) Singhal, Anupam
    This solid waste may contaminate surface run-off and surface water. In stainless steel pickling industries, a lot of sludge is generated and disposal of above sludge as per Act of Hazardous Waste (Management & Handling) Rules, 1989 is not easy. In the normal practice, the sludge is being disposed off on both sides of roads and railway tracks to fill low lying areas. This causes a severe problem, because during rains, the entire toxic compound (leachate) goes into ground and pollutes the ground water. Seeing the above problem, a study is taken for utilization of pickling sludge with fly ash to avoid the problem of disposal. Cement concrete hollow cavity bricks can be made and compressive strength of cement concrete hollow cavity brick is found to increase with addition of 7.5% TSLS (treated spent liquor sludge) and 15% fly ash as a partial replacement of cement. Formation of C-S-H gel may be contributing to increase in compressive strength.
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    Trials on sludge of lime treated spent liquor of pickling unit for use in the cement concrete and its leaching characteristics
    (2007) Singhal, Anupam
    Disposal of sludge of lime treated spent liquor pickling unit, as per the Act of Hazardous Waste (Management and Handling) Rules, 1989 is not easy. Its transportation and construction of lined disposal sites pose very severe problem. In the normal practice, sludge is being disposed off on sides of roads and railway tracks to generally fill the low-lying areas. This may cause severe health hazards. An attempt has therefore been made to utilize the treated spent liquor sludge in cement concrete. Design mix M20 has been prepared with varying concentration of sludge in the laboratory. Toxicity characteristics leaching procedure (TCLP) test as per USEPA has been carried out on cement concrete cubes