Waste to Catalyst: Synthesis of Catalysts from Sewage Sludge of the Mining, Steel, and Petroleum Industries

Abstract

The generation of sewage sludge presents a problem for several manufacturing companies as it results from industrial processes or effluent treatment systems. The treatment of this type of waste requires high economic investment, for this reason, it is necessary to find alternatives to recover the valuable materials of the sludges. In this study, metal catalysts were synthesized using waste sludge from the steel, mining, and hydrocarbon industries. The waste sludge was subjected to thermal treatments for the removal of organic content and the reduction of metals with hydrogen current to activate their catalytic properties. The sludge and synthesized catalysts were analyzed to determine their physical, chemical, thermoenergetic, and catalytic properties. Catalytic activity was evaluated using CO chemisorption and by thermal–catalytic decomposition of crude oil. The best conditions for synthesizing the catalysts were a calcination temperature between 300 and 500 °C and a reduction temperature between 300 and 900 °C. The catalysts presented a specific surface between 2.33 and 16.78 m2/g. The catalytic material had a heat capacity between 0.7 and 1.2 kJ/kg∙K. The synthesized materials presented catalytic activity comparable to that of commercial catalysts. With this recovery technique, the industrial waste can be valorized, obtaining catalyst derived from the sludges and promoting the circular economy of manufacturing companies.

Wet Air Oxidation Route for the Synthesis of Organomineral Fertilizers from Synergistic Wastes (Pomace and Kimberlite)

“…The transformation of wastes through catalysis as a source of valuable mineral and bioactive compounds has gained more attention in the scientific community in recent years, ,, promoting valorization, nutrient recovery, and circular economy in food and mining industries while solving a long-standing problem caused by the linear economy. Martinez-Fernandez et al proposed the extraction of valuable bioactive nutrients (e.g., polyphenols and polysaccharides) from potato peels, another organic waste that is underutilized, using a hydrothermal process and also observed the opportunity of recovering solubilized nutrients in water and the solid-phase byproduct as a low-cost fertilizer due to phosphate and nitrogen content.…”

“…30,31 Kimberlite has also been used for the formation of functional soil 29 and recently as a catalyst. 32 The catalyst potential is mainly considered due to the high surface area of the fine and porous mineral and the transition-metal content, which includes significant ferrous iron (Fe 2+ ) content that could act in the faster generation of a strong organic oxidant agent (i.e., hydroxyl radical) during WO. Also, the presence of valuable mineral nutrients for plants, such as magnesium, potassium, and silicon, 31 opens the opportunity for this mineral to be combined with OM for the production of an organomineral fertilizer, 33−35 as was studied in this work for the case of catalytically wet oxidized GP and kimberlite.…”

“…Kimberlite is mined in diamond-prone environments by drilling, blasting, grinding, washing, and detailed screening for precious gems, and these activities produce massive amounts of waste in open fields (i.e., tailings) . The use of kimberlite waste to replace cement in building materials, while capturing CO 2 via mineral carbonation and thus offsetting industrial carbon emissions has been attempted. , Kimberlite has also been used for the formation of functional soil and recently as a catalyst . The catalyst potential is mainly considered due to the high surface area of the fine and porous mineral and the transition-metal content, which includes significant ferrous iron (Fe 2+ ) content that could act in the faster generation of a strong organic oxidant agent (i.e., hydroxyl radical) during WO.…”

Catalytic Cooperation between a Copper Oxide Electrocatalyst and a Microbial Community for Microbial Electrosynthesis

“…[30] Furthermore, several methods have been described to recover copper from waste, [31] including the synthesis of catalysts from waste. [32] Particularly the use of copper as a cathodic electrocatalyst could possibly further decrease the environmental impact due to leaching, as copper can be recovered from the electrolyte via electrodeposition. [22] Taken together, while an impact analysis of the use of copper was not part of this study, copper is expected to be a promising catalyst for the development of co-catalytic concepts in combination with microbial catalysts.…”

“…Therefore, a proof‐of‐principle of catalytic cooperation between naturally‐occurring microorganisms and copper may allow to envision various co‐catalytic routes, based on the unique product spectrum of copper, for final products of longer carbon chains and with higher value, compared to acetate and methane, such as butyrate, isobutyrate, [28] caproate, [29] and caprylate [30] . Furthermore, several methods have been described to recover copper from waste, [31] including the synthesis of catalysts from waste [32] . Particularly the use of copper as a cathodic electrocatalyst could possibly further decrease the environmental impact due to leaching, as copper can be recovered from the electrolyte via electrodeposition [22] .…”