Sludge based micro-electrolysis filler for removing tetracycline from solution

Sludge-derived iron-carbon material enhancing the removal of refractory organics in landfill leachate: Characteristics optimization, removal mechanism, and molecular-level investigation

Mature landfill leachate is a refractory organic wastewater, and needs physical and chemical pretreatments contemporaneously, e.g. iron-carbon micro-electrolysis (IC-ME). In this study, a novel iron-carbon (Fe-C) material was synthesized from waste activated sludge to be utilized in IC-ME for landfill leachate treatment. The pyrolysis temperature, mass ratio of iron to carbon, and solid-liquid ratio in leachate treatment were optimized as 900 °C with 1.59 and 34.7 g/L. Under these optimal conditions, the chemical oxygen demand (COD) removal efficiency reached 79.44 %, which was 2.6 times higher than that of commercial Fe-C material (30.1%). This excellent COD removal performance was indicated to a better mesoporous structure, and uniform distribution of zero-valent iron in novel Fe-C material derived from sludge. The contribution order of COD removal in IC-ME treatment for landfill leachate was proven as coagulation, adsorption, and redox effects by a contrast experiment. The removal of COD includes synthetic organic compounds, e.g. carcinogens, pharmaceuticals and personal care products. The contents of CHO, CHON, and CHOS compounds of dissolved organic matter (DOM) in the leachate were decreased, and both the molecular weight and unsaturation of lipids, lignin, and tannic acids concentration were also reduced. Some newly generated small molecular DOM in the treated leachate further confirmed the existence of the redox effect to degrade DOM in leachate. The total cost of sludge-derived Fe-C material was only USD$ 152.8/t, which could save 76% of total compared with that of commercial Fe-C materials. This study expands the prominent source of Fe-C materials with excellent performance, and deepens the understanding of its application for leachate treatment.

Facile fabrication of Eu-based metal-organic frameworks for highly efficient capture of tetracycline hydrochloride from aqueous solutions

The tetracycline hydrochloride (TCH) removal from wastewater is important for the environment and human health yet challenging. Herein, the Eu-based MOF, Eu(BTC) (BTC represents 1,3,5-trimesic acid) was prepared by an efficient and environmental-friendly strategy, and then was used for the TCH capture for the first time. The Eu(BTC) was characterized by different methods such as X-ray diffraction, scanning electron microscopy and Fourier-transform infrared spectroscopy. The TCH uptake of Eu(BTC) was investigated systematically. The influences of experiment conditions such as solution pH value, adsorption time and initial concentration on TCH capacity of Eu(BTC) were also studied. The Eu(BTC) obtained exhibited remarkable TCH uptake (q_m was up to 397.65 mg/g), which was much higher than those of most materials such as UiO-66/PDA/BC (184.30 mg/g), PDA-NFsM (161.30 mg/g) and many carbon-based materials reported till now. Besides, the TCH adsorption behavior on Eu(BTC) was explored by Freundlich and Langmuir equations, and the adsorption mechanism was further analyzed. The experimental results suggested that the TCH adsorption mechanism of Eu(BTC) included the π-π interaction, electrostatic interaction and coordinate bonds. The excellent TCH adsorption performance and the efficient fabrication strategy make the Eu(BTC) prepared promising in TCH removal.

Preparation of sludge-based micro-electrolysis filler and its application in pharmaceutical wastewater treatment by an up-flow aerated filter

Sewage sludge (SS) and raw pharmaceutical wastewater (RPW) are both toxic and harmful wastes, which are a menace to human and animal health and the ecosystem. A sludge-base micro-electrolysis filler (SMEF) was gained by SS and Fe powder as the primary raw materials. The preparation process of the SMEF was achieved based on the tetracycline hydrochloride (TCH) removal efficiency. The physicochemical characteristics (e.g., surface area, morphology features, function groups, and valence state of Fe) of the obtained SMEF were decided. With an Fe/SS ratio of 1/2, a sintering temperature of 1050 °C, a sintering time of 30 min, an initial pH of 3, and a filler dosage of 100 g/L, the SMEF demonstrated a high degradation ability for TCH with a removal rate reached 95.62% in 24 h. Kinetic analysis showed that the adsorption process of TCH was consistent with the pseudo-first-order Lagergren kinetic model. Moreover, degradation mechanism analysis showed that TCH was gradually degraded through dehydroxylation, demethylation, ring opening, oxidation, and reduction in solution. The SMEF had a good continuous removal performance for contaminants in RPW in an up-flow aerated filter. The removal efficiency of TOC and TN reached 46.60 and 42.27% within 24 h, respectively. The treated pharmaceutical wastewater was considered non-biotoxic after 24-h treatment with the SMEF. This study presents a innovative Fe-C micro-electrolysis filler based on SS and is important to the environmental-friendly recycling of SS and sustainable treatment of RPW, achieving the purpose of waste disposal.

MOF-derived biochar composites for enhanced high performance photocatalytic degradation of tetracycline hydrochloride

Biochar reinforced advanced nanocomposites are of interest to a wide circle of researchers. Herein, we describe a novel MOF-derived reinforced cow dung biochar composite, which was prepared by a one-step hydrothermal method to form the MOF MIL-125(Ti) onto a nitrogen and sulfur co-doped bio-carbon (NSCDBC). The UV-vis diffuse reflectance spectrum of NSCDBC/MIL-125(Ti) exhibits an extension of light absorption in the visible region (360–800 nm), indicating its higher visible light capture capacity relative to pure MIL-125(Ti). The photocatalytic activity results show that all the NSCDBC/MIL-125(Ti) composite samples, namely NSCM-5, NSCM-10, NSCM-20 and NSCM-30 display good performance in the removal of tetracycline hydrochloride compared to pure MIL-125(Ti). Among them, NSCM-20 exhibits the highest catalytic activity with a removal rate of 94.62%, which is attributed to the excellent adsorption ability of NSCDBC and the ability to inhibit the complexation of photogenerated electron–hole pairs. Photoluminescence verifies that the loading of biochar successfully enhances the separation of photogenerated electron–hole pairs. Subsequently, the active species in the photocatalytic process are identified by using electron spin resonance spin-trap techniques and free radical trapping experiments. Finally, the possible reaction mechanism for the photocatalytic process is revealed. These results confirm that NSCDBC/MIL-125(Ti) is a potentially low-cost, green photocatalyst for water quality improvement.

Schematic diagram of fabricating process of NSCDBC/MIL-125(Ti).

Iron-carbon microelectrolysis for wastewater remediation: Preparation, performance and interaction mechanisms

Rapid industrialization and urbanization have produced a lot of hazardous substances in water and wastewater, which has turned into a crucial issue to the environment and the public health. Recently, iron carbon microelectrolysis (IC-ME) has attracted extensive attention in environmental remediation due to its low costs and excellent performance. Nevertheless, there is still a lack of a more systematic review on IC-ME preparation methods, their performance, and the interaction mechanisms of IC-ME in the remediation of wastewater. Herein, this work summarizes the synthetic methods, application of IC-ME materials, and the mechanism of pollutant removal by IC-ME. A variety approaches have been applied to prepare IC-ME materials, and the preparation methods and conditions have a certain influence on the properties of IC-ME materials, thus affecting the performance of pollutant removal. The mechanisms of IC-ME for contaminants removal are very complex, including adsorption, coprecipitation, reduction, surface complexation, and oxidation. Moreover, research vacant fields and problems that existed in the application of IC-ME are proposed. At last, the problems to be addressed to adapt IC to future applications are introduced. This paper reviews and prospects IC-ME wastewater remediation technology, which provides a reference for further scientific research and engineering applications.

Prepartion and application of novel blast furnace dust based catalytic-ceramic-filler in electrolysis assisted catalytic micro-electrolysis system for ciprofloxacin wastewater treatment

Blast furnace dust (BFD), a hazardous metallurgical waste, is generated during the iron-making process and consists plenty of Fe and C. This study is among the first to apply BFD in catalytic-ceramic-filler (CCF) preparation and degradation of ciprofloxacin (CIP). The novel BFD based Fe-Ni CCF obviously enhanced the removal of CIP (from around 42%-72% after 3 h) in comparation with troditional Fe-C ceramic-filler(CF). The Fe-Ni CCF was further applied in a coupled system of electrolysis assisted catalytic micro-electrolysis (E-CME) process for CIP wastewater treatment. Under optimal operating conditions (iron rod as anode, voltage of 10v and HRT of 3 h), nearly 97% of CIP, 90% of total organic carbon (TOC) and 99% of total phosphorus (TP) were removed by E-CME process in near-neutral solution. The degradation mechanism analysis by LC-MS revealed that polyhydroxy sub-stituted, piperazine rings cleavage and so on were the main reaction of CIP in E-CME process. Additionally, the chemical oxygen demand (COD) residue after E-CME process could be effectively eliminated by up-flow anaerobic filter (UAF), owing to the significant improvement of wastewater biodegradability by E-CME pretreatment. This study provides a new way for co-friend recycling of BFD and a highly-efficient, cost-sffective technology for CIP wastewater treatment.

Enhanced Simultaneous Nitrogen and Phosphorus Removal in A Denitrifying Biological Filter Using Waterworks Sludge Ceramsite Coupled with Iron-Carbon

In this study, waterworks sludge ceramsite (WSC) was combined with 3% iron-carbon matrix in a denitrifying biological filter (ICWSC-DNBF) to enhance the simultaneous removal of carbon, nitrogen and phosphorus in secondary effluent of wastewater treatment plant (SE-WTP). The chemical oxygen demand (COD) and nitrogen removal, as well as phosphorus removal and the adsorbed forms of phosphorus were measured and the removal mechanism of these pollutants by the ICWSC-DNBF system for treating SE-WTP were investigated. The results showed that the ICWSC-DNBF achieved good removals of COD, NH₄⁺-N, NO₃^--N, total N and total P; effluent concentrations were 17.23 mg/L, 3.72 mg/L, 14.32 mg/L, 17.38 mg/L and 0.82 mg/L, respectively. WSC enhanced the P removal due to its high specific surface area and the high number of adsorption sites. Fe-P and Al-P were the main forms of P adsorbed by WSC, accounting for 78.53% of the total adsorbed P. WSC coupled with Fe and C improved the biodegradability of SE-WTP and promoted the removal of organic matter. The removal of N was attributed to the abundant denitrifying microorganisms in the system and the electrochemical effect produced by the internal electrolysis of Fe and C.