Addition of MnO2 in synthesis of nano-rod erdite promoted tetracycline adsorption

Abstract

Erdite is a rare sulphide mineral found in mafic and alkaline rocks. Only weakly crystallised fibrous erdite has been artificially synthesised via evaporation or the hydrothermal method, and the process generally requires 1–3 days and large amounts of energy to complete. In this study, well-crystallised erdite nanorods were produced within 3 h by using MnO2 as an auxiliary reagent in a one-step hydrothermal method. Results showed that erdite could synthesised in nanorod form with a diameter of approximately 200 nm and lengths of 0.5–3 μm by adding MnO2; moreover, the crystals grew with increasing MnO2 addition. Without MnO2, erdite particles were generated in irregular form. The capacity of the erdite nanorods for tetracycline (TC) adsorption was 2613.3 mg/g, which is higher than those of irregular erdite and other reported adsorbents. The major adsorption mechanism of the crystals involves a coordinating reaction between the −NH2 group of TC and the hydroxyl group of Fe oxyhydroxide produced from erdite hydrolysis. To the best of our knowledge, this study is the first to synthesise erdite nanorods and use them in TC adsorption. Erdite nanorods may be developed as a new material in the treatment of TC-containing wastewater.

Upcycling of Fe-bearing sludge: preparation of erdite-bearing particles for treating pharmaceutical manufacture wastewater

“…(1)-(3)) to generate Fe oxyhydroxide and release HS − to the supernatant. In the presence of enough dissolved oxygen, redox reaction between HS − and dissolved oxygen occurred with the generation of sulphur 17 . The newly formed Fe oxyhydroxide had a special structure in which one Fe atom had an average coordination number of hydroxyl group of 5.4, which is higher than that of aggregated ferrihydrite and hematite 36 .…”

“…Amongst Fe-bearing minerals, erdite is a special 1-D nanomaterial comprising (FeS 2 ) n n- 16 . It is metastable in neutral and mildly acidic solutions and is easily decomposed into Fe oxyhydroxide and S-containing compounds 17 . The new Fe oxyhydroxide has numerous surface hydroxyl groups, similar to the hydrolysed product of a polyferric sulphate flocculant, and exhibits high adsorption capacity for arsenic 18 , rare-earth metals 19 and phosphate 20 .…”

Upcycling of Electroplating Sludge to Prepare Erdite-Bearing Nanorods for the Adsorption of Heavy Metals from Electroplating Wastewater Effluent

“…Secondly, a replacement reaction between free HS − and the hydroxyl group of Fe(OH) 4 − occurred, thereby generating Fe(OH) 3 HS − (Equation (2)), followed by the conjunction reaction between two adjacent Fe(OH) 3 HS − compounds. Thus, Fe 2 S 2 (OH) 4 2− was generated with the dewatering of two water molecules (Equation (3)) [37]. Finally, the conjunction reaction continued in the presence of sufficient Fe(OH) 4 − to form the final product (FeS 2 ) n n− .…”

Recycling of High-Purity Strontianite and Hematite from Strontium-Bearing Sludge

“…Such defects limit the applications of this method for high-purity Sr recovery. In addition, Fe is an active cation and easily reacts with precipitators, such as sulfide, hydroxide, and carbonate. − This characteristic accounts for the high Fe impurity concentrations of recycled Sr-bearing products. Therefore, Fe should be removed prior to Sr removal in Sr separation from Sr-bearing leachate.…”

“…Fe is rapidly hydrolyzed into Fe oxyhydroxide in the leachate and further converted into highly crystallized Fe oxides, e.g., akageneite and hematite. ,− Lu et al achieved approximately 30% Fe and 0.1% Cu removal from Fe/Cu-bearing leachate generated through chalcopyrite leaching with hydrochloric acid and subsequent hydrothermal treatment at 155 °C for 60 min . Fe removal rates can be increased to above 85% when the temperature is increased to 200 °C and to nearly 90.7% in the presence of H 2 O 2 .…”