Study on the efficacy and mechanism of treatment of manganese-containing wastewater by pulse-alternating current coagulation.

To assess the effectiveness and underlying mechanism of pulse-alternating current coagulation (PACC) for treating manganese-laden wastewater, we examined the influence of various parameters. Specifically, we investigated the impact of current density, initial pH, initial Mn2+ concentration, electrolyte concentration, and alternating current frequency on the removal efficacy. The removal mechanism was meticulously examined using an adsorption kinetics analysis, Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectrum (FTIR), and X-ray Photoelectron Spectroscopy (XPS). The findings indicated that the concentration of Re(Mn2+) was 99.09% under the specified conditions: j = 2.5 A·m-2, pH0 = 7, c0(Mn2+) = 50 mg·dm-3, f = 500 Hz, c0(NaCl) = 500 mg·dm-3 and t = 40 min. When Re(Mn2+) = 98%, the energy consumption (EEC) was significantly lower for PACC at 1.23 kWh·m-3, compared to 1.52 kWh·m-3 for direct current condensation (DCC). This indicated a reduction in EEC by 19.1% when using PACC over DCC. The adsorption process of Mn2+ by the iron sol adheres to the principles of pseudo-second order kinetics. The primary component of flocs generated in the PACC process is α-FeOOH. The mechanism of Mn2+ removal in the PACC process involved the synthesis of Mn oxides, the formation of metal hydroxide precipitates and adsorption by nano-iron sol. This study provides a theoretical basis and technical support for the application of PACC technology in the field of manganese-containing wastewater treatment.

High-intensity mechanical bowel preparation before curative colorectal surgery is associated with poor long-term prognosis.

PURPOSE: Mechanical bowel preparation (MBP) has been widely used to reduce intestinal feces and bacteria and is considered necessary to prevent surgical infections. However, it is still controversial which intensity level of MBP is the most beneficial for patients before colorectal surgery. Our study aimed to determine the impact of different intensity levels of MBP on the progression-free survival (PFS) and overall survival (OS) for colorectal cancer (CRC) patients. METHODS: We evaluated 694 patients pathologically diagnosed with CRC and underwent MBP before surgery at 4 general hospitals from January 2011 to December 2015. The survival status of patients, the disease progression, and the time of death or progression were obtained through telephone follow-up at the deadline October 10, 2018. Hazard ratios were estimated by Cox proportional hazard models. Survival was assessed using the Kaplan-Meier method followed by the log-rank test. RESULTS: Of 694 patients included, 462 received low-intensity MBP and 232 received high-intensity MBP. A significantly higher PFS in low-intensity MBP was observed (p = 0.009). PFS at 2000 days was 69.331% in the low-intensity arm and 58.717% in the high-intensity arm. Patients who underwent low-intensity MBP also showed higher OS (p = 0.009). Nine patients in the low-intensity MBP group received secondary surgery, and two patients in the high-intensity MBP group received secondary surgery. CONCLUSIONS: In this retrospective cohort, low-intensity MBP was associated with better PFS and OS, which could provide a reference for doctors when choosing the intensity of MBP.

Study on removal of phosphorus and COD in wastewater by sinusoidal AC Fenton oxidation-coagulation.

In order to treat domestic wastewater containing phosphorus and chemical oxygen demand (COD), the new technology of Sinusoidal Alternating Current (AC) Fenton Oxidation-Coagulation (SACFOC) was used to improve the removal efficiency (Re) and reduce energy consumption (EEC). The morphology, elemental composition, crystal structure and functional groups of the sludge were characterised by Scanning Electron Microscope (SEM), Energy-dispersive X-ray Spectroscopy (EDS), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The results show that total phosphorus removal efficiency {Re(TP)} and removal efficiency of organic matter {Re(COD)} can reach 97.56% and 87.77%, respectively, but EEC is only 0.09 kWh·m-3 under the optimum conditions of pH0 = 3, current density (j) = 0.5 A·m-2, c0(TP) = 18 mg·dm-3, c0(COD) = 300 mg·dm-3, c0(H2O2) = 0.06 mol·dm-3, t = 45 min. As compared with direct current (DC) Fenton Oxidation-Coagulation (DCFOC), the COD removal efficiency of SACFOC treatment was improved by 37%, but the energy consumption was reduced by 45%. The degradation process of total phosphorus and COD by SACFOC abides by the quasi-first-order kinetic model. The process of SACFOC includes double effects of electrocoagulation of iron sol by electrolysis and degrade COD by oxidation of formed hydroxyl radicals (·OH) in wastewater, which improves removal efficiency of total phosphorus and COD in wastewater. Our research findings will provide technical guidance and a theoretical basis for the simultaneous treatment of wastewater containing phosphorus and COD applying SACFOC process.

Effect of iron ion configurations on Ni2+ removal in electrocoagulation.

Electrocoagulation (EC) has been widely used to treat the heavy metal wastewater in industry. A novel process of sinusoidal alternating current electrocoagulation (SACC) is adopted to remove Ni2+ in wastewater in this study. The morphology of precipitates and the distribution of the main functional iron configurations were investigated. Ferron timed complex spectroscopy can identify the monomeric iron configurations [Fe(a)], oligomeric iron configurations [Fe(b)] and polymeric iron configurations [Fe(c)]. The optimal operating conditions of SACC process were determined through single-factor experiments. The maximum Ni2+ removal efficiency [Re(Ni2+)] was achieved under the conditions of pH0=7, current density (j) = 7 A/m2, electrolysis time (t) = 25 min, c0(Ni2+) = 100 mg/L. At pH=7, the proportion of Fe(b) and Fe(c) in the system was 50.4 at.% and 23.1 at.%, respectively. In the SACC process, Fe(b) and Fe(c) are the main iron configurations in solution, while Fe(c) are the vast majority of the iron configurations in the direct current electrocoagulation (DCC) process. Re(Ni2+) is 99.56% for SACC and 98.75% for DCC under the same optimum conditions, respectively. The precipitates produced by SACC have a high proportion of Fe(b) configurations with spherical α-FeOOH and γ-FeOOH structures which contain abundant hydroxyl groups. Moreover, it is demonstrated that Fe(b) has better adsorption capacity than Fe(c) through adsorption experiments of methyl orange (MO) dye. Fe(a) configurations in the homogeneous solution had no effect on the removal of nickel.