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Summary Aqueous CO2-containing environment is ubiquitous in oil and gas production. Carbonate scales (e.g., calcite) tend to form in such an environment. Meanwhile, the CO2 corrosion of mild steel infrastructure may result in corrosion-induced scales including siderite (FeCO3). Previously, siderite was generally treated as a corrosion problem rather than a scale problem. However, the relationship between the corrosion-induced scale and other metal carbonate scales on the steel surface is unclear. For example, how does siderite influence calcite deposition on the mild steel? In this study, the mild steel corrosion and mineral carbonate scaling behaviors were investigated simultaneously in the presence of various cations such as Ca2+ and Mg2+. We observed a two-layer scale structure on the mild steel surface under simulated oilfield conditions. The inner layer is an iron-containing carbonate scale such as ankerite or siderite, while the outer layer is calcite. In addition, calcite deposition at a very low saturation index was observed when the inner layer was present. Furthermore, a common scale inhibitor [diethylenetriaminepentakis(methylenephosphonic acid) or DTPMP] can effectively mitigate calcite, siderite, and ankerite formation on the steel surface, but meanwhile, aggravate the steel corrosion because of the absence of protective scale layers.

Regenerable methods for phosphate (P) recycling have received intense attention due to their potential environmental and economic benefits. In this study, to improve the electrosorptive removal of P in membrane capacitive deionization, an activated carbon (AC) electrode was coated with a heterogeneous anion-exchange resin layer, and named the AE-AC composite electrode. It was shown that the AE-AC electrode exhibited a good capacitive behavior for electrical double-layer charging. The batch-mode experiments indicted that when the solution pH changed from 5 to 8, the predominant P species shifted from monovalent H2PO4− to divalent HPO42− that was preferentially electroadsorbed for competitive electrosorption with Cl−. Importantly, the AE-AC composite electrode significantly increased the selectivity coefficient of P over Cl− to 0.56 that was 2.24-fold greater than that of the uncoated AC electrode, at 1.2 V in single-pass mode operation. This improvement can be ascribed to the preferential transport of P through the thin coating layer containing quaternary amine functional groups. The permselectivity of the coating also significantly increased the electrosorption capacity of P from 0.031 to 0.101 mmol/g with a high charge efficiency (97%) by the reduction in the co-ion repulsion effect. When the reverse voltage (−1.2 V) was applied, electroadsorbed P was reversibly desorbed from the AE-AC electrode in repeated operation. This work suggests that coating an anion-exchange resin layer on the surface of a carbon electrode shows great potential to improve the selective removal of P through electrosorption.

Recently, sulfide scale related issues have been significantly increased, probably due to implementation of more aggressive technologies and exploration of unconventional fields, such as high temperature, high pressure, and high salinity. Firstly, sulfide scales (i.e., FeS, PbS, and ZnS) are one of the most or significantly unsolved deposition problem in oil and gas production. Secondly, sulfide scales have oleophilic nature so that they can be difficult to separate sulfide scales from oil phase during production processes. Polymeric dispersants have exhibited their feasibility to prevent the deposition of sulfide scales, but dispersants have not been widely validated to control sulfide scale problems and limited numbers of trials and reports have been available. The objectives of this study are: (1) to evaluate dispersion efficiency of sulfide scale dispersants in a wide range of conditions of brine ionic strength, calcium concentrations, solution pH, and temperature; (2) to examine the effect of dispersants on sulfide scale wettability; (3) to understand the mechanism of a dispersion process; and (4) to apply the newly developed dispersion model for a prediction of a minimum dispersant concentration (MDC). Among tested natural and synthetic water-soluble polymers, carboxymethyl cellulose (CMC) showed the best dispersion efficiency for sulfide scales with an individual particle size of around 4 nm. The second-best dispersants identified in our study were polyvinyl pyrrolidone (PVP) and polyacrylamide (PAM). Despite some degrees of aggregation of dispersed sulfide particles, their size was still in the nanometer ranges of 100 to 500 nm. Dispersed sulfide particles remained in the water phase, while settled ones were transferred to the oil phase. Transmission electron microscope (TEM) and Fourier-transform infrared (FT-IR) results showed that CMC was adsorbed on the surface of FeS particles through H-bond and complexation between Fe(II) and carboxylate groups, controlling particles growth and preventing them from settling. CMC was effective to disperse sulfide scales in conditions of brine ionic strength (58.5 – 234 g/L NaCl), Ca2+ concentrations (1,000 – 8,000 mg/L), pH (4.3 – 6.7), and temperature (70 – 120 °C). In these reaction conditions, MDC of CMC ranged from 5 to 200 mg/L. The combination of CMC and diethylenetriamine penta(methylene phosphonic) acid (DTPMP) enhanced CMC dispersion efficiency in some conditions. MDC of CMC for PbS and ZnS scales were 2 and 5 mg/L, respectively. MDC prediction model predicted MDC quite reasonably in wide range of NaCl concentrations (58.5 – 234 g/L) and SI of FeSm (0.13 – 2.03).

This study aims to explore the effects of different biochar applications on soil physical and chemical properties in a

High-efficiency recycling technology for endangered elements effectively mitigates the risk of resource shortages and promises the sustainability of supply chains, which is significant to the industry. In this study, an activated carbon (AC)-based capacitive deionization (CDI) for the selective electrosorption and recovery of indium ions (In3+) from acidic aqueous solution is proposed. The effects of applied voltage, pH, and initial concentration of indium were investigated to optimize the operation parameters for In3+ electrosorption. The results of cyclic voltammetry and the galvanostatic charge/discharge measurements indicate that the AC electrode shows good capability for the electrosorption of In3+ based on electrical double-layer capacitance. As demonstrated, In3+ can be successfully removed by CDI without deposition when the pH

In this study, we employed carbon nanotubes (CNTs) to improve the performance of flow-electrode capacitive deionization (FCDI) for wastewater desalination in isolated closed-cycle (ICC) mode. The effects of CNTs loading and initial salt concentration on FCDI desalination were evaluated with energetic performance analysis. FCDI was carried out for the desalination with real wastewater for technology demonstration. The addition of CNTs significantly improved the average salt removal rate (ASRR), associated with a decrease in the flow-electrode flowability. FCDI with 0.25 wt% CNTs had an ASRR of 1.59 μmol/cm2–min, which was 1.7-fold higher than that without CNTs. This was attributed to the bridging effect of CNTs for more rapid charge transfer. Increasing the initial salt concentration from 0.05 to 0.30 M led to a higher ASRR, resulting from a reduction in the electrical resistance in the cell. After further increasing the salt concentration to 0.50 M, the charge efficiency was relatively decreased due to co-ion leakage. Notably, FCDI for the desalination of real saline wastewater achieved a high decrease in conductivity (94%), a high charge efficiency (>99%), and low energy consumption (0.034 kWh/mol). Our results demonstrated that adding CNTs is a feasible approach to achieve high-performance FCDI for sustainable wastewater desalination.

In order to reveal the effect of vegetation type and soil physicochemical properties on the distribution of soil organic carbon and its components, a field survey was carried out on nine different plant communities along a water table gradient in the Huixian wetland with samples of soil at 0-10 cm, 10-20 cm, and 20-30 cm in depth. The soil organic carbon (SOC), light fraction organic carbon (LFOC), heavy fraction organic carbon (HFOC), easily oxidized organic carbon (EOC), dissolved organic carbon (DOC), particulate organic carbon (POC), and microbial biomass carbon (MBC) were measured. The correlations among soil organic carbon components and soil physicochemical properties were also examined. The results showed that:① The average proportion of LFOC and HFOC to SOC at 0-30 cm soil depth was 11.10% and 88.90%, respectively. The distribution ratio of the heavy component was much higher than of the light component in soils. ② The content of SOC, DOC, EOC, POC, and MBC (except in the

This study aims to scale up a membrane capacitive deionization (MCDI) stack for the reuse of domestic wastewater for industry applications. The desalination performance of the pilot-scale MCDI was investigated for the removal of ions from the effluent of a domestic wastewater treatment plant in terms of water quality, ion selectivity, water productivity and fouling/scaling phenomena. The MCDI stack was composed of 40 pairs of 20 cm × 20 cm activated carbon electrodes and operated in a single-pass mode. The MCDI stack achieved good removal efficiency of ions from the wastewater effluent (up to 94% Ca2+ and 84% NO3−). For electrode regeneration, the pump-off operation enabled a much higher water recovery of 75%. In particular, the average conductivity after the MCDI treatment was 103 μS/cm, which meets the standard for industrial reuse. For the electrosorption selectivity of cations, Ca2+ and Mg2+ were favored due to their high charge. Among the anions, NO3− had the highest electrosorption selectivity owing to its hydration ratio. Notably, the water quality of MCDI-treated effluents remained stable during consecutive charging-discharging cycles over 5 months of operation. These results provide essential data to scale up the MCDI stack with application to water reclamation.

To investigate the effect of reclamation on soil quality in the Huixian Karst Wetland, samples from different soil levels were collected from marsh wetland, reclaimed paddy field, and reclaimed dry farmland, for analyzing soil nutrient (carbon, nitrogen, phosphorous, and potassium) contents, microbial biomass carbon/nitrogen (MBC/MBN), and microbial activity indicators[i.e. basal respiration (BR), potential respiration (PR), microbial quotient (qMB), and metabolic quotient (qCO