Feasibility of microwave remediation of simulative crude oil-contaminated soil assisted by bluecoke-based modifiers.

Microwave (MW) remediation of organics-contaminated soil technology offers the advantages of high efficiency and minimal damage, representing a new approach of soil thermal remediation. However, soil, being a weak MW-absorbing medium, struggles to convert MW energy into thermal energy, thus failing to attain the necessary temperature for thermal remediation. This paper prepared two new bluecoke (BC)-based modifiers (KHCO3@BC and KHCO3/MnO2@BC) to address temperature problem of MW remediation, as well as enhance soil quality. Their composition, structure and electromagnetic properties were analyzed to investigate their role in assisting with the MW remediation of an artificially crude oil-contaminated soil were investigated. Additionally, the industrial feasibility of MW remediation was addressed for the first time. The results showed that the KHCO3 and MnO2 particles in the two modifiers were covered on the BC surface and exhibited local agglomeration. Their carbon crystalline grain size increased, and the electromagnetic properties were weaker than those of the BC. Following 10 min of MW remediation assisted by KBC or KMnBC, the remediation temperatures exceeded 300 °C, with the removal rates of PHs reaching 76.16% and 88.31%, respectively. The organic matter content, soil potassium and mechanical fraction of the remediated soil were improved, but soil acidification still needed to be further addressed. The industrial application analysis indicated that the technical process and techno-economics of MW remediation of crude oil-contaminated soil were feasible, suggesting significant potential for the large-scale industrial application.

Insights into removal efficiency and mechanism of microwave remediation of soils contaminated with polyaromatic hydrocarbons of low molecular weight assisted by bluecoke-based conditioner.

Microwave remediation of polyaromatic hydrocarbons-contaminated soils has garnered extensive attention owing to its cost effectiveness, time saving, homogeneous heating, and low energy consumption. The prepared bluecoke-based conditioner (KHCO3@BC) was used in this study to enhance microwave remediation and improve the naphthalene (NA) removal efficiency and soil properties. We investigated the optimal conditions, including the heating time, microwave power, bluecoke-based conditioner, initial concentration of NA, and moisture content of the soils. We evaluated the removal efficiency of NA and compared the remediation products after the addition of bluecoke, KHCO3, and KHCO3@BC conditioners. The results showed that the removal efficiency of NA reached 96.46% under the following optimized conditions: heating time of 20 min, microwave power of 700 W, 2 g of KHCO3@BC conditioner, initial NA concentration of 1 wt%, and soil moisture content of 4 wt%. The KHCO3@BC conditioner improved the contents of total K and fast-acting K during microwave remediation, and the mechanical components of the remediation soils were also optimized significantly. We proposed a feasible mechanism and evaluated the main reasons for the removal of NA from the soils based on the mechanical components of remediation soil and the remediation products, namely, gas stripping, boiling vaporization of NA, and breakage of soil grains by thermal stress.

Wear Behaviors of AISI 4145H Drilling Tool Steel under Drilling Fluid Environment Conditions.

4145H steel is a commonly used material for downhole tools. However, up to now the wear behavior of 4145H drilling tool steel under real drilling fluid environment conditions is still not clear. In this work, this was investigated using a modified ASTM B611 rubber ring wet grinding test system, in which six kinds of abrasives (talc, dolomite or fluorite, as well as their mixed abrasive with quartz) with metal hardness-to-abrasive hardness ratios (H/HA) ranging from 0.25 to 6.25 were used in the drilling fluid for experiments. The results show that the H/HA value determined the wear mechanism of 4145H steel. When a single soft abrasive was used (with H/HA higher than 1.3-1.5), polishing was the dominantly observed mechanism. While mixed abrasives were applied, a microcutting mechanism due to the ploughing of hard abrasive particles on the steel surface was also observed. The increase in mass fraction of the soft abrasives has little effect on the wear rate of 4145H steel, but its wear rate will significantly increase as the mass fraction of hard abrasives increases. Therefore, in order to extend the life of drilling tools and reduce downhole accidents, the mass fraction of hard particles in the drilling fluid should be reduced as much as possible.

Stabilization of Soil Arsenic with Iron and Nano-Iron Materials: A Review.

Soil arsenic (As) contamination is an important environmental problem, and chemical stabilization is one of the major techniques used to remediate soil As contamination. Iron and iron nanoparticle materials are widely used for soil As stabilization because they have one or more of the following advantages: high adsorption capacity, high reduction capacity, cost effectiveness and environmental friendliness. Therefore, this review introduces the stabilization of soil As with iron and iron nanoparticles, including zero-valent iron, iron oxides/hydroxides, some iron salts and Fe-based binary oxides and the nanoparticles of these iron materials. The mechanism of chemical soil As stabilization, which involves adsorption and the coprecipitation process, is discussed. The factors affecting the chemical stabilization process are presented, and challenges to overcome in the future are also discussed in this review.

High mercury leachate containing HgS22- complex ion: Detoxifying solidification and high efficiency Hg extraction.

Clean and efficient treatment of high-mercury leachate produced from remediation of mercury-polluted soil has become a huge challenge for environmental scientists. In this work, cement solidification was firstly adopted to treat the high-concentration mercury leachate, which had high alkalinity. Different mercury concentrations, namely 3.120mg/L Hg mercury leachate and 9.243mg/L Hg mercury concentrated leachate, were separately solidified by Portland cement. The results indicated that simply using the cement can properly solidify both the leachates to meet the waste landfill standard, with liquid (mL)/solid (g) ratio (L/S ratio) of 4:10-6:10. In order to make full use of mercury in the leachates, a Hg extraction method was subsequently carried out under different experimental parameters, such as temperature and pH value. It was shown that the Hg extraction ratio could reach as high as 99.84% and almost all the mercury in the leachate could be transformed to HgS precipitate; moreover, the Hg concentration in the treated leachate was reduced from 3.120 to 0.005mg/L at pH2.98 and 30°C, which was much less than the limit of the national standard, indicating that the leachate had been completely cleaned and could be discharged freely. Hence, simple cement solidification renders high-mercury leachate nontoxic, and the Hg extraction method can successfully recover the Hg and enable the residual leachate to be discharged safely.

Multiple copper adsorption and regeneration by zeolite 4A synthesized from bauxite tailings.

Copper ions were first adsorbed by zeolite 4A synthesized from bauxite tailings, the desorption of Cu(II) using Na2EDTA solutions was performed, and the recycling of zeolite 4A in adsorption and desorption was systematically investigated. It was observed that the Cu(II) removal efficiency was directly dependent on the initial pH value. The maximum removal efficiency of Cu(II) was 96.2% with zeolite 4A when the initial pH value was 5.0. Cu(II) was completely absorbed in the first 30 min. It was also observed that the desorption efficiency and zeolite recovery were highly dependent on the initial pH and concentration of Na2EDTA in the solution. The desorption efficiency and percent of zeolite recovered were 73.6 and 85.9%, respectively, when the Na2EDTA solution concentration was 0.05 mol L-1 and the pH value was 8. The recovered zeolites were pure single phase and highly crystalline. After 3 cycles, the removal efficiency of Cu(II) was as high as 78.9%, and the zeolite recovery was 46.9%, indicating that the recovered zeolites have good adsorption capacity and can repeatedly absorb Cu(II).