Factors affecting the leaching of heavy metals (Ni⁺², Pb⁺², Cr⁺³) contained in sludge waste stabilization/solidification by hydraulic benders, Part I: water/cement and waste/cement ratio in S/S mortars

Abstract

The aim of the present paper is to investigate the effect of the water/cement ratio (w/c) (0.4 and 0.6) and the amount of hazardous waste (W/c) (10, 20, 25, 30, and 45%) incorporated on the leaching of heavy metals from a cementitious solidified materials. Mechanical strength of the S/S materials was evaluated at 28 days of cure. Specimens that have shown a good mechanical strength for the two water/cement ratios were used to make this study succeed. XRD analysis has shown the presence of heavy metals within the structure of S/S materials which explains immobilization of heavy metals contained in the waste by the S/S process. Amount of heavy metals released to the environment was evaluated by several leaching tests, namely, TCLP (toxicity characteristic leaching procedure), pore water (PW) and maximum mobile fraction (MMF), and monolithic leaching test (MLT). Monolithic specimens were evaluated under dynamic leaching conditions for 64 days with periodic leachant renewal on two aggressive media, sulfatic attack and in demineralized water. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 93–103, 2017

Efficiency of stabilization/solidification of heavy metals contained in hydroxide sludge waste into metakaolin based geopolymers

“…The release of the chlorides depends on the quantity of the waste added since the latter is contained just in the raw waste, the same result were found with the S/S mortars studied previously [23]. Calcium is contained in the metakaolin used for the synthesis of the geopolymer in small amount and in the waste with a large amount and, therefore, its release obviously depends on the amount of waste added.…”

“…Average concentrations of heavy metals namely: Ni, Cr, and Pb are very large and far exceed the standards required by the regulations [34]. More information can be found in previous study [23]. All results obtained has shown that this waste is hazardous and must be stabilized before its disposal.…”

“…Characterization of this waste by means of aqua regia digestion, XRD, and SEM analysis have shown that this ultimate waste is hazardous and must be stabilized before its disposal. Stabilization in the form of mortars has shown that this treatment is efficient for water to cement ratio of 0.4 and by incorporating 30% of waste in the formulation of the mortar . It should be noted that ordinary portland cement (OPC) is the most used material in the construction industry worldwide, it has a high level of CO 2 emissions (1 ton of cement generates 1 ton of CO 2 ).…”

Chromium(VI) removal by bone char–ZnO composite: Parameters optimization by response surface methodology and modeling

“…Freundlich equation is the description of multilayer, uniform, and heterogeneous adsorption of the adsorbate on the adsorbent. The Freundlich model is [34] q e 5K f C e 1=n (6) where K f is the adsorption capacity (mg/g) and 1/n is the adsorption intensity.…”

Comparison of arsenic immobilization properties among calcium silicate hydrate, ettringite, and friedel's salt in a slag‐based binder

“…Numerous treatment methods, such as vitrification, acid extraction, adsorption, and solidification/stabilization (S/S), have been developed to prevent arsenic and heavy metal contamination . To date, S/S with ordinary Portland cement is the most common method for arsenic‐containing waste disposal .…”