Waste Remediation Research Articles

Photocatalytic Gold Recovery from Industrial Gold Plating Effluent by ZnO Nanoparticles: Optimum Condition and Possible Applications.

The comparative study of photocatalytic gold recovery from cyanide-based gold plating solution was explored via commercial and hydrothermally synthesized ZnO nanoparticles (NPs). The effects of hydrothermal temperatures on the properties and photocatalytic activities of synthesized ZnO NPs were investigated. In addition, the effects of operating parameters including types of hole scavenger, concentrations of the best hole scavenger, the initial pH of wastewater, and photocatalyst dosages were examined. The obtained results demonstrated that the commercial ZnO NPs exhibited a higher photocatalytic activity for gold recovery than that of the synthesized ones owing to their good crystal quality and the presence of non-lattice zinc ions and appropriate non-lattice oxygen ions. Via the commercial ZnO NPs, the gold ions were almost completely recovered from the cyanide-based gold plating effluent within 7 h at an initial pH of 11.0 in the presence of 10 vol % C2H5OH and 1.0 g/L of photocatalyst loading with a pseudo-first-order rate constant of 0.2637 h-1. Finally, the resultant gold-decorated ZnO NPs exhibited a higher photocatalytic property for color reduction from industrial wastewater and antibacterial activity than that of fresh ZnO NPs. The results obtained in this study possess benefits and pave the way for waste remediation and management for the plating industries.

MXene/AgNW composite material for selective and efficient removal of radioactive cesium and iodine from water

Toxic fission products, such as cesium (137Cs) and iodine (129I) are of great concern because of their long half-lives and high solubility in water. The simultaneous removal of Cs and I using a single adsorbent is an area of increasing interest. In this study, MXene/silver nanowire (AgNW) composite was synthesized through physical mixing and employed for simultaneous removal of iodide (I−) and cesium (Cs+) ions from contaminated water. The MXene/AgNW composite demonstrated excellent adsorption capacities of 84.70 and 26.22 mg/g for I− and Cs+, respectively. The experimental data supported the hypothesis of multilayer adsorption of Cs+ owing to the inter-lamellar structures and the presence of heterogeneous adsorption sites in MXene. The interaction between I− and the AgNW involved chemisorption followed by monolayer adsorption. MXene/AgNW composite material exhibited promising results in the presence of competitive ions under extreme pH conditions. Thus, synthesized composite materials holds promising potential as an adsorbent for the remediation of radioactive liquid waste.

Studies on the Sonochemical assisted Oxidation Reaction of Potassium Iodide for Iodine Release using Ultrasound

Ultrasound (US) application and sonochemical reactions in various environmental processes are gaining importance. In this regard, liberation of iodine obtained through oxidation of potassium iodide (KI) using US has been studied in the present work. This method finds wide application of oxidation process in various applications such as unit process reactions, synthetic chemistry as well as waste remediation. Process parameters such as time and ultrasound power have been investigated. Liberation of iodine from the reaction system has been analyzed using UV-Visible spectrophotometric method through iodometry. Maximum liberation of iodine was obtained using ultrasound (25 W, 20 kHz) for 30 minutes treatment with 10 ml of 16.6% KI solution. The study finds potential use in sonochemical based oxidation reactions and environmental processes.

Evaluation of ecotechnology performance in treating textile wastewater: constructed treatment wetlands and natural adsorbents

The development of environmentally friendly technology for water ecosystem rehabilitation has become a challenge in solving pollution control problems in water bodies. Ecotechnology is a technology to improve water quality using an ecosystem approach, including the technology of constructed treatment wetlands and natural adsorbents. This study aims to produce an alternative ecotechnology for textile industrial waste remediation, on-site treatment of water bodies contaminated with textile waste, using a constructed treatment wetlands system and natural adsorbents. The result was conducted for 6 months using a reactor on a pilot scale with a continuous system. The result showed that CTWs’ ability effectively reduced ammonia in textile wastewater with a 20% dilution of up to > 80% and > 90% respectively using plants Vetiveria zizanioides and Heliconia psittacorum. Meanwhile, at 50% textile wastewater dilution, CTW with Heliconia psittacorum was more effective in reducing ammonia (> 80%) than CTW with Vetiveria zizanioides (> 60%). CTW with Vetiveria zizanioides and Heliconia psittacorum was able to reduce the dye content up to < 69.68% and < 54.39%, respectively. The natural adsorbent ability of bentonite has a higher ability to reduce dyes and ammonia, which is up to < 64.84% and < 91.12%. Good performance in these two eco-technology systems will result in better waste disposal by combining these two systems into one ecotechnology system.

Mercury Levels in Groundwater near Artisanal Small-Scale Gold Mines in Migori County, Kenya

In Migori County, artisanal and small-scale gold mining (ASGM) is an economic activity that uses mercury during the amalgamation process to obtain gold. The waste generated in the form of soil tailings and pan-pond water contains mercury and is located close to community boreholes. The proximity may predispose groundwater to mercury contamination. Boreholes are one of the main water sources in Migori County. Ingestion is one of the ways mercury can get into the human body. This study was conducted to establish mercury concentration in groundwater from boreholes, soil tailings and pan-pond water located near five mine sites in Migori County during dry and wet seasons in comparison with drinking water standards required by KEBS and NEMA effluents discharge standards. The five mines were: -Masara, Osiri Matanda, Macalder, Kitere and Kehancha. The study used a cross-sectional-analytical study design and focused on boreholes found within a distance of 6 km from each of the five mines. Fifteen boreholes were proportionately sampled to obtain groundwater samples. 20 pan-pond water and soil tailing samples were collected in both dry and wet seasons as per the respective sampling protocols applied. Inductively Coupled Plasma –Mass Spectroscopy (7900 ICP-MS) was used to measure mercury levels. A paired t-test was used to compare the means of the levels of mercury in groundwater obtained within the two seasons. The study established that during the dry season, all of the boreholes had groundwater mercury levels higher than the recommended limit by KEBS of 0.001 mg/L. There was a decrease in the levels of mercury in groundwater as distances from the mine increased. However, during the wet season, all of the boreholes had mercury levels below the limit of detection. The study established a significant difference in the levels of mercury in groundwater between wet and dry seasons at a 95% confidence level. Mercury levels in soil tailings and pan-pond water were above the NEMA effluents discharge standards of 0.05 mg/kg and 0.05 mg/L, respectively, in the dry season. During the wet season, all pan-pond water achieved the recommended mercury level of NEMA effluent discharge limits, while the soil tailings had mercury levels above the recommended limit. This study recommends that there is a need to implement mine waste remediation. Communities near the mines continuously conduct groundwater heavy metal analysis during the dry season to protect their health

Kinetics of the Temperature-Dependent eaq - and ⋅OH Radical Reactions with Cr(III) Ions in Aqueous Solutions.

The reactivity of chromium(III) species with the major oxidizing and reducing radiolysis products of water was investigated in aqueous solutions at temperatures up to 150 °C. The reaction between the hydrated electron (eaq - ) and Cr(III) species showed a positive temperature dependence over this temperature range. The reaction was also studied in pH 2.5 and 3.5 solutions for the first time. This work also studied the reaction between acidic Cr(III) species and the hydroxyl radical (⋅OH). It was found that Cr3+ did not react significantly with the ⋅OH radical, but the first hydrolysis species, Cr(OH)2+ , did with a rate coefficient of k= (7.2±0.3)×108 M-1 s-1 at 25 °C. The oxidation of Cr(OH)2+ by the ⋅OH radical formed an absorbing product species that ultimately oxidized to give Cr(VI). These newly measured reaction rates allow for the development of improved models of aqueous chromium speciation for the effective remediation of liquid high-level nuclear waste via vitrification processes.

Metal Sulfide Ion Exchangers: High Acid Stability of Na2xMg2y-xSn4-yS8 (NMS) and Topotactic Conversion to 2D Solid Acids with Semiconducting Character.

Metal sulfide ion exchange materials (MSIEs) are of interest for nuclear waste remediation applications. We report the high stability of two structurally related metal sulfide ion exchange materials, Na2xMg2y-xSn4-yS8 (Mg-NMS) and Na2SnS3 (Na-NMS), in strongly acid media, in addition to the preparation of Na2xNi2y-xSn4-yS8 (Ni-NMS). Their formation progress during synthesis is studied with in-situ methods, with the target phases appearing in <15 min, reaction completion in <12 h, and high yields (75-80%). Upon contact with nitric or hydrochloric acid, these materials topotactically exchange Na+ for H+, proceeding in a stepwise protonation pathway for Na5.33Sn2.67S8. Na-NMS is stable in 2 M HNO3 and Mg-NMS is stable in 4 M HNO3 for up to 4 h, while both NMS materials are stable in 6 M HCl for up to 4 days. However, the treatment of Mg-NMS and Na-NMS with 2-6 M H2SO4 reveals a much slower protonation process since after 4 h of contact both NMS and HMS are present in the solution. The resultant protonated materials, H2xMg2y-xSn4-yS8 and H4x[(HyNay-1)1.33xSn4--1.33x]S8, are themselves solid acids and readily react with and intercalate a variety of organic amines, where the band gap of the resultant adduct is influenced by amine choice and can be tuned within the range of 1.88(5)-2.27(5) eV. The work function energy values for all materials were extracted from photoemission yield spectroscopy in air (PYSA) measurements and range from 5.47 (2) to 5.76 (2) eV, and the relative band alignments of the materials are discussed. DFT calculations suggest that the electronic structure of Na2MgSn3S8 and H2MgSn3S8 makes them indirect gap semiconductors with multi-valley band edges, with carriers confined to the [MgSn3S8]2- layers. Light electron effective masses indicate high electron mobilities.

Rational design of MOF@COF composites with multi-site functional groups for enhanced elimination of U(VI) from aqueous solution

Both environment and human beings were menaced by the widespread application of radioactive uranium, high-performance and effective elimination of uranium from wastewater is of important meaning for development of environmental sustainability in the future. In this study, the water-stable MOF material and the highly crystalline COF were compounded by a mild hydrothermal strategy, which achieved efficient removal of U(VI) through the synergistic effect. The composites showed the characteristics of both COFs and MOFs, which will possess higher stability, larger surface area and faster adsorption efficiency that cannot be carried out by a single component. Batch experiments and characterizations (SEM, TEM, XRD, FT-IR, BET, XPS, etc.) indicated that UiO-66-NH2@LZU1 had more stable and multi-layer pore structure and rich active functional groups. The Langmuir model and the pseudo-second-order kinetics fitting was more suitable for the U(VI) elimination process. The greatest uranium adsorbing capacity of UiO-66-NH2@LZU1 (180.4 mg g−1) was observed to exceed the UiO-66-NH2 (108.8 mg g−1) and COF-LZU1 (65.8 mg g−1), which reached the excellent hybrid effects. Furthermore, FT-IR and XPS analyses confirmed that the most nitrogen-containing group from COF-LZU1 and oxygen-containing group of UiO-66-NH2 could be combined with U(VI). In addition, electrostatic interaction was also a mechanism during the removal process. This work displayed that UiO-66-NH2@LZU1 was a prospective hybrid material for radioactive waste remediation. The compound method and application mentioned in this work had provided a theoretical basis for designing and developing multi-functional composite adsorbents, which contributed to the development of new materials for radioactive wastewater treatment technologies.

A review of the chemical synthesis of magnetic nano-particles and biomedical applications

Magnetic nano-particles are nano-particles that can be altered using magnetic fields. Due to their widespread attention magnetic nano-particles are used for several biomedical applications. Magnetic nano-particles, in general, have unique magnetic properties that enable them to be controlled and optimized for specific uses. Considering that it can produce the appropriate size, structure, morphology, and magnetic control, chemical synthesis based on solution-phase reactions has gotten a lot of interest. Magnetic nanoparticles have emerged as an effective tool for water waste remediation. In this review paper first, we have discussed some of the important methods by which magnetic nano-particles can synthesize. A brief discussion of magnetic nano-particles was then presented, including their applications in biomedicine, such as drug delivery, MRI, and hyperthermia. The application of magnetic nano-particles in agriculture and environmental treatment is summarized in this section. Also, the design and synthesis of magnesia materials intended for biological applications is included in this article.

Environmental cost and financial performance of listed oil and gas companies in Nigeria

This study is aimed at investigating the relationship between Environmental Cost and Environmental Performance of Oil and gas companies in Nigeria. The study employed historical data design. Census Sampling Techniques was used in studying the entire population. Multiple regressive with the help of ordinary least square was used. Findings revealed that the amount spent on waste management and remediation has a negative and insignificant relationship with both growth in sales volume and return on assets. It was, however, recommended that oil and gas companies should continue to manage their waste, and include community development in their decision making. It is in line with global best practices to keep them socially accepted as these will ensure a symbiotic relationship among various stakeholders or their host communities.

Simultaneous removal of sulfide and bicarbonate from synthetic wastewater using an algae-assisted microbial fuel cell

ABSTRACT The anaerobic digestion (AD) process is one of the most practiced technologies for the remediation of organic waste and maximization of energy recovery in terms of biogas or biomethane. The presence of other gaseous components in biogas, e.g. CO2 and H2S, often makes its direct application in engines and electricity production unsuitable. This work aimed to develop and utilize an algae-assisted microbial fuel cell (AMFC) for the purification of biogas by removing both CO2 and H2S and simultaneous bioelectricity generation. In addition to biogas clean-up, elemental sulfur recovery and CO2 utilization for algae cultivation add value to the proposed AMFC process. Experiments were performed with both sulfide and bicarbonate in their dissolved form, in the respective anodic and cathodic chambers of the AMFC. The sulfide concentration was varied from 100 to 800 mg/l and the AMFC exhibited a sulfide removal efficiency exceeding 97% at all concentrations tested. The process efficiency dropped, however, at sulfide concentrations above 300 mg/l in terms of both sulfide removal and power output. The AMFC performed best at 400 mg/l sulfide by exhibiting a power density of 24.99 mW/m3 and sulfide removal efficiency of 98.87%. The system exhibited columbic efficiency (CE %) in the range of 7.85–80%. The total alkalinity representing CO2, carbonate and bicarbonate levels in the algae-based system was reduced by 49.54%. The electrical energy recovered from the AMFC was 0.1 kWh/m3 and the total energy recovery, which is the sum of the electrical and algal lipid energy, amounted to 7.25 kWh/m3.

Waste remediation: Low-temperature synthesis of hybrid Cu(OH)2/CuO and CuO nanostructures from spent printed circuit boards and their dye degradation studies.

The demand for environmentally friendly and sustainable resource utilization techniques for recycling waste printed circuit boards is significant due to their status as valuable secondary resources, containing high-purity copper and precious metals. In this context, Cu(OH)2/CuO and CuO nanostructures were fabricated using alkaline precipitation and low-temperature aging methods using the strip solution originated from laboratory-scale spent mobile phone printed circuit board recovery process. XRD, FTIR, FESEM-EDX, and TEM were utilized to characterize the as-recovered nanoproducts. A hybrid structure of Cu(OH)2/CuO was formed at 70°, and monoclinic CuO phase was formed at 80°C aging time. The results show that Cu(OH)2/CuO nanoflakes have an average crystallite size of 24.06nm and a particle width of 22 ± 3nm. Cu(OH)2/CuO nanoflakes formed at 70°C aging temperature and 24-h residence time have finer crystallite and particle sizes than CuO-ridged nanospheres formed at 80°C aging temperature. The optical band gap energy of Cu(OH)2/CuO and CuO nanostructures formed was found to be 2.28eV and 2.22eV, respectively. The hybrid Cu(OH)2/CuO nanostructure photocatalyzed the decomposed 97.28% rhodamine blue using a visible light source, whereas the CuO nanostructure degraded only 14.64% rhodamine blue dye under similar conditions. A surfactant-less hybrid structure is developed without the use of any chemical precursor. Thus, a high value-added product is produced using one waste material to remove another waste in wastewater treatment.

Deep insight on mechanism and contribution of arsenic removal and heavy metals remediation by mechanical activation phosphogypsum

Arsenic-containing wastewater and arsenic-contaminated soil can cause serious environmental pollution. In this study, phosphogypsum with partial mechanical activation of calcium oxide was used to prepare a new phosphogypsum-based passivate (Ca-mPG), and its remediation performance on arsenic-contaminated soil was evaluated in terms of both effectiveness and microbial response. The results showed that the optimum conditions for the preparation of the passivate were optimized in terms of single factor and response surface with a ball milling speed of 200 r/min, a material ratio of 6:4 and a ball milling time of 4 h. Under these conditions, the adsorption capacity was 37.75 mg/g. The leaching concentration of arsenic (As) in the contaminated soil after Ca-mPG modification decreased from 25.75 μg/L to 5.88 μg/L, which was lower than the Chinese national standard (GB/T 5085.3–2007); Ca-mPG also showed excellent passivation effect on other heavy Metals (copper, nickel, cadmium, zinc). In addition, As-resistant bacteria and passivators work together to promote the stabilization effect of contaminants during the remediation of As-contaminated soil. The mechanisms of Cu, As(III)/As(V), Zn, Cd, and Ni removal were related to ion exchange, electrostatic adsorption of substances on heavy metals, calcium binding to other substances to produce precipitation; and microbially induced stabilization of HMs, oxidized. Overall, this study demonstrates an eco-friendly "waste-soil remediation" strategy to solve problems associated with solid waste reuse and remediation of HM-contaminated soils.

Treatment of textile wastewater using carbon-based nanomaterials as adsorbents: a review.

Waste derived from the textile industry can contain a wide variety of pollutants of organic and inorganic natures, such as dyes (e.g., acid, basic, reactive, mordant dyes) and toxic metals (e.g., lead, chromium, cadmium). The presence of pollutants at high concentrations in textile waste makes them relevant sources of pollution in the environment. To solve this problem, various technologies have been developed for the removal of pollutants from these matrices. Thus, adsorption emerges as an efficient alternative for textile waste remediation, providing advantages as simplicity of operation, economy, possibility of using different adsorbent materials, and developing on-line systems that allow the reuse of the adsorbent during several adsorption/desorption cycles. This review will initially propose an introduction to the adsorption world, its fundamentals, and aspects related to kinetics, equilibrium, and thermodynamics. The possible mechanisms through which a pollutant can be retained on an adsorbent will be explained. The analytical techniques that offer valuable information to characterize the solid phases as well as each adsorbate/adsorbent system will be also commented. The most common synthesis techniques to obtain carbon nano-adsorbents have been also presented. In addition, the latest advances about the use of these adsorbents for the removal of pollutants from textile waste will be presented and discussed. The contributions reported in this manuscript demonstrated the use of highly efficient carbon-based nano-adsorbents for the removal of both organic and inorganic pollutants, reaching removal percentages from 65 to 100%.

An Intensive Study on Algal Diversity in the Ancient Man-Made Aquatic Ecosystem of Tiruvallur, South India: Exploration for Sustainable Development.

Eco-friendly and beneficial nature algae make it prominent in our earth as well as for human life. In recent decades, microalgal applications is sought in varied fields from the remediation of wastes to the production of pharmaceutical products. Still, more extensive research on bioprospecting should to conducted to get the genus-specific or species-specific applications of microalgae with high efficiency. This inquiry was carried out (October 2021 to September 2022) for the effectual understanding of microalgal composition structure along with seasonal physicochemical variations in the age-old holy tank at Tiruvallur, southeast India. This inquiry also acts as the source data and makes the bioprospecting process easier. It also ignites the researchers to address the microalgae seasonal composition structure of peculiar wet environments. A total of 41 microalgae species were recorded, in which six major algal groups were in order of, Chlorophyceae > Bacillariophyceae > Cyanophyceae > Euglenophyceae > Zygnematophyceae > Trebouxiophyceae. Mean seasonal abundance was highest in the summer season (351 cells/L) and lowest in the monsoon (113 cells/L). One-way ANOVA showed seasonal variations of physicochemical parameters, in which the majority of them attained their peak during summer. Mean values of water temperature, pH, salinity, total dissolved solids, total solids, electrical conductivity, chemical oxygen demand, total hardness, total alkalinity, ammonia, nitrite-nitrogen, and nitrate-nitrogen for the summer were 31.43°C, 8.53, 0.56 ppt, 383mg/L, 525mg/L, 0.85 mS/cm, 46.27mg/L, 300ppm, 251.67ppm, 1.51mg/L, 0.62mg/L, and 0.70mg/L, respectively. Karl Pearson's correlation revealed a most significant relationship between water quality factors and algal density. The Shannon's diversity index (2.78-3.39) indicated moderately rich microalgal diversity in the study area. Palmer's pollution index stated that the temple tank was organically polluted all over the study period except November.

Influence of kepok banana bunch as new cellulose source on thermal, mechanical, and biodegradability properties of Thai cassava starch/polyvinyl alcohol hybrid-based bioplastic.

Bioplastics were developed to overcome environmental problems that are difficult to decompose in the environment. This study analyzes Thai cassava starch-based bioplastics' tensile strength, biodegradability, moisture absorption, and thermal stability. This study used Thai cassava starch and polyvinyl alcohol (PVA) as matrices, whereas Kepok banana bunch cellulose was employed as a filler. The ratios between starch and cellulose are 10:0 (S1), 9:1 (S2), 8:2 (S3), 7:3 (S4), and 6:4 (S5), while PVA was set constant. The tensile test showed the S4 sample's highest tensile strength of 6.26 MPa, a strain of 3.85%, and a modulus of elasticity of 166 MPa. After 15 days, the maximum soil degradation rate in the S1 sample was 27.9%. The lowest moisture absorption was found in the S5 sample at 8.43%. The highest thermal stability was observed in S4 (316.8°C). This result was significant in reducing the production of plastic waste for environmental remediation.

Recent advancement in nanomaterials for the detection and removal of uranium: A review

Uranyl ions U(VI), are the common by-product of nuclear power plants and anthropogenic activities like mining, excess utilization of fertilizers, oil industries, etc. Its intake into the body causes serious health concerns such as liver toxicity, brain damage, DNA damage and reproductive issues. Therefore, there is urgent need to develop the detection and remediation strategies. Nanomaterials (NMs), due to their unique physiochemical properties including very high specific area, tiny sizes, quantum effects, high chemical reactivity and selectivity have become emerging materials for the detection and remediation of these radioactive wastes. Therefore, the current study aims to provide a holistic view and investigation of these new emerging NMs that are effective for the detection and removal of Uranium including metal nanoparticles, carbon-based NMs, nanosized metal oxides, metal sulfides, metal-organic frameworks, cellulose NMs, metal carbides/nitrides, and carbon dots (CDs). Along with this, the production status, and its contamination data in food, water, and soil samples all across the world are also complied in this work.

Continuous flow synthesis of Ag-PEDOT-COF nanocomposite for sustainable photoreforming of plastic waste and chromium remediation in visible light

Using the freely available solar energy for photocatalytic environmental remediation is a highly sustainable approach. Visible light active heterogeneous photocatalysts are to be developed for driving such reactions. Heterojunction nanocomposites of conjugated polymers with metals as well as other semiconductors are highly active photocatalysts. However, the synthesis of these materials involves multi-step reactions and harsh reaction conditions. Here, we report a single-step continuous flow synthesis of a nanocomposite (Ag@PEDOT-DAAQ-TFPFlow), containing a conducting polymer (PEDOT), silver (Ag) nanoparticles and a covalent organic framework (COF, DAAQ-TFP). The nanocomposite could be synthesised at a lower temperature and in less time when compared to a two-step batch process. Moreover, Ag@PEDOT-DAAQ-TFPFlow exhibited higher surface area and porosity than Ag@PEDOT-DAAQ-TFPBatch. Further, the former has improved ability to absorb light in a broad range, efficiently generate charge carriers and transfer them than the latter as well as Ag@PEDOT and, DAAQ-TFP. Thus, Ag@PEDOT-DAAQ-TFPFlow could be used as an efficient photocatalyst for photoreforming plastic waste to green hydrogen (113.4 mmolgcat-1h-1) and other value-added products such as formate, acetate, terephthalate, and lactate. It is also one of the best visible light active photocatalysts for the reduction of toxic Cr (VI) to Cr (III). Thus, the enhanced mixing profile and better heat/mass transfer in the continuous flow synthesis process enabled us to achieve a highly active photocatalyst.

Mechanistic insights into Pb and sulfates retention in ordinary Portland cement and aluminous cement: Assessing the contributions from binders and solid waste

Identifying immobilization mechanisms of potentially toxic elements (PTEs) is of paramount importance in the field application of solidification/stabilization. Traditionally, demanding and extensive experiments are required to better access the underlying retention mechanisms, which are usually challenging to quantify and clarify precisely. Herein, we present a geochemical model with parametric fitting techniques to reveal the solidification/stabilization of Pb-rich pyrite ash through conventional (ordinary Portland cement) and alternative (calcium aluminate cement) binders. We found that ettringite and calcium silicate hydrates exhibit strong affinities for Pb at alkaline conditions. When the hydration products are unable to stabilize all the soluble Pb in the system, part of the soluble Pb may be immobilized as Pb(OH)2. At acidic and neutral conditions, hematite from pyrite ash and newly-formed ferrihydrite are the main controlling factors of Pb, coupled with anglesite and cerussite precipitation. Thus, this work provides a much-needed complement to this widely-applied solid waste remediation technique for the development of more sustainable mixture formulations.

Synergistic adsorption and degradation of sulfamethazine by tobacco stalk-derived activated biochar: Preparation, mechanism insight and application

Green preparation of high value-added products from biomass waste for environmental remediation has received significant attention. In this work, activated biochars were developed through two-step thermal process using tobacco stalk as the precursor. Textural properties of biochar can be effectively tuned by adjusting carbonization and activation parameters. An optimized biochar (700TS-1000–5), carbonized at 700 ℃ and then thermally activated at 1000 ℃ for 5 h, showed higher specific surface area (905.61 m2 g−1), rich porous structure, and abundant surface functional groups. 700TS-1000–5 showed excellent performance with a removal capacity of 99.37 mg g−1 for sulfamethazine (SMT) in 720 min, which was 4.3 times that of pristine biochar (700TS). And the SMT removal was high-efficient under normal environmental pH range. Adsorption and degradation simultaneously occurred during the whole process, which mainly relied on defects, functional groups, and·OH radicals. Moreover, this typical sample showed outstanding recycling ability and effectiveness of column experiment. Compared with KOH-assisted chemical activation, thermal activation had minor environmental impact and lower preparation cost through environmental and economic assessment. These findings not only propose a simple protocol for high-value reuse of agricultural waste but also shed new light on applications of tobacco stalk-derived biochar.