Synthesis and properties of SrFe_(12)O_(19) obtained by solid waste recycling of oily cold rolling mill sludge

The aim of this study was to develop a new approach for the preparation of environmentally friendly, high-value products from oily cold rolling mill(CRM) sludge. Utilizing oily CRM sludge as a source of iron, strontium hexaferrite(SrFe_(12)O_(19)) powders were prepared by multi-step processes involving acid leaching, chemical conversion treatment, and synthesis by a citrate precursor. The influences of citric acid dosage and the pH of the sol system on the formation, crystallite size, and magnetic properties of the obtained SrFe_(12)O_(19) powders were investigated. High saturation magnetization(74.8 mA·m^2·g^(–1)) and intrinsic coercivities(614.46 mT) were achieved for pH 7.0 of the sol system, for which the molar ratio of citric acid dosage to the total dosage of Fe^(3+) and Sr^(2+) was 1.5. This study presents a new approach to utilizing oily CRM sludge, and even refractory iron-containing solid waste.

Preparation and hydration of industrial solid waste-cement blends:A review

Industrial solid waste(ISW)-cement blends have the advantages of low carbon,low energy consumption,and low pollution,but their clinker replacement level in low carbon cement is generally low.To address this challenge,this study considers the latest progress and development trends in the ISW-cement blend research,focusing on the activation of ISWs,the formation of ISW-cement blends,and their associated hydration mechanisms.After the mechanical activation of ISWs,the D50(average size)typically drops below 10μm,and the specific surface area increases above 350 m2/kg.Thermal activation can increase the glassy-phase content and reactivity of ISWs,where the coal gangue activation temperature is usually set at 400-1000°C.Furthermore,the roles of ISWs in the hydration of ISW-cement blends are divided into physical and chemical roles.The physical action of ISWs usually acts in the early stage of the hydration of ISW-cement blends.Subsequently,ISWs participate in the hydration reaction of ISW-cement blends to generate products,such as C-(A)-S-H gels.Moreover,alkali activation affects the hydration kinetics of ISW-cement blends and modifies the proportion of gels.Environmental impacts and costs of ISW-cement blends have also been discussed to guide stakeholders in selecting sustainable ISWs.

Phase evolution and properties of glass ceramic foams prepared by bottom ash,fly ash and pickling sludge

Municipal solid waste incineration products of bottom ash(BA),fly ash(FA),and pickling sludge(PS),causing severe environ-mental pollution,were transformed into glass ceramic foams with the aid of CaCO3 as a pore-foaming agent during sintering.The effect of the BA/FA mass ratio on the phase composition,pore morphology,pore size distribution,physical properties,and glass structure was investigated,with results showing that with the increase in the BA/FA ratio,the content of the glass phase,Si-O-Si,and Q3Si units decrease gradually.The glass transmission temperature of the mixture was also reduced.When combined,the glass viscosity decreases,causing bubble coalescence and uneven pore distribution.Glass ceramic foams with uniform spherical pores are fabricated.When the content of BA,FA,and PS are 35wt%,45wt%,and 20wt%,respectively,contributing to high performance glass ceramic foams with a bulk density of 1.76 g/cm3,porosity of 56.01%,and compressive strength exceeding 16.23 MPa.This versatile and low-cost approach provides new insight into synergistically recycling solid wastes.

Enrichment of Ni-Mo-V via pyrometallurgical reduction from spent hydrogenation catalysts and the multi-reaction mechanism

Spent hydrogenation catalysts are important secondary resources due to richness in the valuable metals of Ni,Mo and V.Recovery of valuable metals from spent catalysts has high economic value and environmental benefits since they are hazardous wastes as well.Traditional recycling processes including hydrometallurgical leaching and soda roasting-leaching have disadvantages such as generating large amounts of wastewater,long process,and low recovery efficiency of valuable metals.Thus,this paper proposed synergistic enrichment of Ni,Mo and V via pyrometallurgical reduction at 1400-1500℃.The melting temperature and viscosity of slag were reduced through slag designing by software FactSage 7.1.The phase diagram of Al_(2)O_(3)-Cap-SiO_(2)-Na_(2)O-B_(2)O_(3)was drawn,and low-temperature region(≤1300℃)was selected as target slag composition.Ni,Mo,and V can be collaborative captured and recovered through the mutual solubility at molten state.Increasing the melting temperature and the amount of CaO,Na_(2)O and C were conducive to improving the metals recovery rates.The kilogram-scale experiments were carried out,and the recovery efficiencies of Ni,Mo and V were 98.3%,95.3%and 97.9%under optimized conditions:at 1500℃,with the basicity of 1.0,13.1 wt%SiO_(2),7.0 wt%B_(2)O_(3),7.7 wt%Na_(2)O and 20.0wt%C.The distribution behavior of valuable metals was clarified by investigating the melting process of slag and the reduction in valuable metals.Ni was preferentially reduced and acted as a capturing agent,which captured other metals to form NiMoV alloys.