Sunflower stalk, an agricultural waste, as an adsorbent for the removal of lead and cadmium from aqueous solutions

Sunflower residue, an agricultural waste material for the removal of lead (Pb) and cadmium (Cd) from aqueous solutions were investigated using a batch method. Adsorbent was prepared by washing sunflower residue with deionized water until the effluent was colorless. Batch mode experiments were carried out as a function of solution pH, adsorbent dosage, initial concentration and contact time. The results indicated that the adsorbent showed good sorption potential and maximum metal removal was observed at pH 5. Within 150 min of operation about 97 and 87 % of Pb and Cd ions were removed from the solutions, respectively. Lead and Cd sorption curves were well fitted to the modified two-site Langmuir model. The adsorption capacities for Pb and Cd at optimum conditions were 182 and 70 mg g^?1, respectively. The kinetics of Pb and Cd adsorption from aqueous solutions were analyzed by fitting the experimental data to a pseudo-second-order kinetic model and the rate constant was found to be 8.42 × 10^?2 and 8.95 × 10^?2 g mg^?1 min^?1 for Cd and Pb, respectively. The results revealed that sunflower can adsorb considerable amount of Pb and Cd ions and thus could be an economical method for the removal of Pb and Cd from aqueous systems.     

Utilization of textile effluent wastewater treatment plant sludge as brick material

In the present work, the feasibility of using sludge generated in wastewater treatment plants of textile industry as a partial replacement for clay in the conventional brick manufacturing process is examined. Physico-chemical properties of the sludge and clay were studied. The characteristics of bricks with replacement of sludge (0–50 %) with an increment of 3 % were determined. All the brick samples satisfied the requirements of Indian Standards norms in terms of weight loss on ignition. The bricks with sludge up to 15 % satisfied the prescribed norms for compressive strength and water absorption. Results also showed that the brick weight loss on ignition was mainly attributed to the organic matter content in the sludge being burnt off during the firing process. The characteristics of bricks such as efflorescence, density and weight loss on ignition for bricks with replacement of clayey soil with textile sludge up to 15 % also satisfied the requirements of the Indian Standard. Thus, textile sludge up to 15 % can be effectively added to make brick material.     

Market potential of biomethane as alternative transportation fuel in South Korea

This study estimated domestically available energy amount of biomethane including landfill gas (LFG) as a transportation fuel by 2035. The amount of available energy that could be supplied was predicted through four stages of ‘theoretical-’, ‘geographical-’, ‘technical-’, and ‘market potential’ by considering geographical, technical, economic conditions, etc. Energy efficiency and added value of biomethane are largely influenced by the site conditions and the neighboring infrastructures. So, how much of the natural gas used in transportation could be substituted with biomethane was examined by setting limits to the amount of organic wastes generated within urban areas. As a result, the market potential of biomethane including landfill gas was approximately 331 × 10⁶ Nm³/year, corresponding to 25% of the natural gas supply for transportation, which could be replaced by biomethane. Assuming that 2% of natural gas for transportation is replaced by biomethane, it corresponds to 29 × 10⁶ Nm³/year (approximately 9% of market potential of biomethane). However, RFS annual mixing rate may be increased upon introduction and the growth rate of the natural gas supply for transport would be higher than that of market potential of biomethane calculated in this study.     

Investigating the performance of aerobic,semi-aerobic,and anaerobic bioreactor landfills for MSW management in developing countries

Three different laboratory bioreactors, each duplicated, with dimensions 0.5 × 0.5 × 1 m were set up and monitored for 160 days. Municipal Solid Wastes with an organic content of ~80 % and a density of 550 kg/m³ were placed in bioreactors. Fresh leachate collected from waste collection vehicles was used with a recirculation rate of 28 L/day. Aerobic bioreactors were aerated at a rate of 0.15–0.24 L/min/kg of waste. Almost the same level of treatment was observed in terms of chemical oxygen demand reduction of leachate, which was in the range of 91–93 %. However, for anaerobic bioreactor, it took almost twice the time, 160 vs. 76 days, to reach the same level of treatment and stabilization. The behavior of semi-aerobic bioreactor was somewhere between the aerobic and anaerobic ones. Total biogas production for anaerobic bioreactors was 90 L/kg of waste, which contained 57–63 % methane. Methane concentration measured in semi-aerobic bioreactor was below 5 %. The main advantage of aerobic bioreactor was the fast rate of the process, while for semi-aerobic bioreactor, it was the elimination of the need for energy to maintain aerobic conditions, and for anaerobic bioreactor it was the production of biogas and potential energy recovery.     

Investigative studies for inert transformation of toxic chrysotile tailing

In an attempt to find ways to reduce consumption of natural raw material and recycle chrysotile tailing waste (CTW), cordierite ceramics were produced using CTW, kaolin tailing waste (KTW) and waste alumina. Before synthesizing the cordierite ceramics, the inert transformation of CTW was investigated via a thermal treatment. Experimental results indicated that CTW was converted into nonhazardous forsterite and enstatite at temperatures above 1000 °C. The characterizations of the synthesized cordierite ceramics were examined using thermal analyses, X-ray diffraction (XRD), morphological structure analyses, compressive strength measurement, coefficient of thermal expansion (CTE) and toxicity characteristic leaching procedure (TCLP). Thermal analyses indicated that significant weight loss below 900 °C was the release of structural water and gases. XRD indicated that the cordierite became the main crystalline phase at 1350 °C. Compressive strength test indicated that compressive strength of the cordierite ceramics was 260 MPa, and CTE of cordierite ceramics was 2.4 × 10^?6 °C^?1. This technology for the of utilization of CTW and KTW could be used to produce industrial cordierite ceramics, in accordance with the concepts of sustainable development.     

Enhanced bioleaching efficiency of copper from waste printed circuit boards (PCBs) by dissolved oxygen-shifted strategy in <Emphasis Type="Italic">Acidithiobacillus ferrooxidans</Emphasis>

Acidithiobacillus ferrooxidans, as chemolithotrophic aerobic bacterium, can obtain energy by oxidation of ferrous ions (Fe²⁺) to ferric ions (Fe³⁺) and use molecular oxygen (O₂) as terminal electron acceptor. In this study, the effects of dissolved oxygen (DO) levels in culture medium on cell growth and copper extraction from waste printed circuit boards (PCBs) were investigated in A. ferrooxidans. The whole culture period was divided into two stages of cell growth and copper extraction. At the former stage, relatively lower DO level was adopted to satisfy bacterial growth while avoiding excessive Fe²⁺ oxidation. At the later stage, higher DO was used to promote copper extraction. Moreover, shift time of DO from lower to higher level was determined via simulating Gauss function. By controlling DO at 10 % for initial 64 h and switching to 20 % afterwards and with 18 g/l PCBs addition at 64 h, final copper recovery reached 94.1 %, increased by 37.6 and 48.3 % compared to constant DO of 10 and 20 % operations. More importantly, copper leaching periods were shortened from 108 to 60 h. It was suggested that application of DO-shifted strategy to enhancing copper extraction from PCBs with reduced leaching periods is being feasible.     

Chitosan Functionalization with Amino Acids Yields to Higher Copper Ions Adsorption Capacity

Chitosan (Chi) beads were conjugated with three different amino acids [namely, glutamic acid (GLU), methionine (MET), and taurine (TAU)] aiming to increase the divalent copper ions uptake in aqueous media. Scanning Electron Microscopy evidenced the development of a large porous structure after amino acid functionalization, associated with the increase in a number of amino groups in the polymer backbone. X-Ray Photoelectron Spectroscopy and Fourier-Transform Infrared Spectra analyses were also employed to assess the conjugation of these three different amino acids in chitosan backbone. Adsorption experiments were conducted in a batch process, at 298 K, and kinetic data indicated a slightly better fitting for the pseudo-first-order model when compared to pseudo-second order. Intraparticle diffusion model suggested a three-step mechanism for Cu(II) adsorption kinetics, limited by the third step, the intraparticle diffusion. The isotherm data fitting to the traditional Langmuir and Freundlich models indicated a better fit for the former case. The amino acid conjugation resulted in the increase of the maximum adsorption capacity for Cu(II) from 1.30 mmol g^?1 prior to amino acid conjugation to values as high as 2.31 mmol g^?1, 2.40 mmol g^?1 and 2.68 mmol g^?1 for Chi–TAU, Chi–GLU, and Chi–MET, respectively. These results are attributed to the introduction of additional amino groups and new carboxylate and amino acid residues into the chitosan backbone, which might also be explored for amino acid demanding applications.     

Investigations on enhanced in situ bioxidation of methane from landfill gas (LFG) in a lab-scale model

The performance of an exogenous bacterium, Methylobacterium extorquens, in inducing bioxidation of methane from landfill gas (LFG) was assessed in a laboratory scale bioreactor. The study show that enhanced oxidation of methane is attained when the bacteria are introduced into the landfill soil. The maximum percentage reduction of methane fraction from LFG when the bioreactor was inoculated with the methanotrophic bacteria was 94.24 % in aerobic treatment process and 99.97 % in anaerobic process. In the experiments with only the indigenous microorganisms present in the landfill soil, the maximum percentage reduction of methane for the same flow rate of LFG was 59.67 % in aerobic treatment and 45 % in anaerobic treatment. The methane oxidation efficiency of this exogenous methanotrophic bacterium can be considered to be the optimum in anaerobic condition and at a flow rate of 0.6 L/m²/min when the removal percentage is 99.95 %. The results substantiate the use of exogenous microorganisms as potential remediation agents of methane in LFG.     

Physical Properties, Photo- and Bio-degradation of Baked Foams Based on Cassava Starch, Sugarcane Bagasse Fibers and Montmorillonite

The objectives of this work were to develop biodegradable trays from cassava starch, sugarcane fibers and Na-montmorillonite (Na-MMT) using a baking process and to study the effects of these components on the physical properties, photo- and bio-degradation of the trays. The sample F20 (produced with 20 g fiber/100 g formulation) showed the maximum yield production (100 %). All formulations resulted in well-shaped trays with densities between 0.1941 and 0.2966 g/cm³. The addition of fibers and Na-MMT resulted in less dense and less rigid trays compared to control samples (only starch). The studied processing conditions resulted in good nanoclay dispersion, leading to the formation of an exfoliated structure. The evaluation of the photo-degradation stability of the trays under UV exposure for 336 h showed that a sample produced with a specific combination of fiber and nanoclay (20 g fiber and 5 g nanoclay/100 g formulation) had the highest loss in stress at break (91 %). Biodegradation assays showed that Control trays (starch) and F20 (20 g fiber/100 g formulation) lost a greater percentage of their weight after 90 days of incubation in soil, with losses of up to 85.50 and 82.70 %, respectively.     

Impact of Cathode Conditions on Coupled Electrochemical Treatment of Nitrate Brine Concentrates

Simulated concentrated nitrate brine waste was treated in a two-stage electrolysis process, where reduction of nitrate in a cathodic chamber was coupled with oxidation of ammonium (produced in the previous stage) in an anodic chamber. The influence of operating conditions such as applied potential, electrolyte composition, and initial concentration on conversion of nitrate to ammonium in the cathodic chamber was investigated. The effects of chloride and current density on the two-stage treatment process were also examined. More negative potential at the cathode (?2.0 vs. ?1.7 and ?1.5 V) and higher current density (33 vs. 22 and 13.9 mA/cm²) favored ammonium as the product of nitrate reduction at a copper cathode and increased the overall amount of nitrate conversion. Faster reduction was seen when nitrate concentration was lower (0.01 vs. 0.02 N), but total mass conversion of nitrate in the same time period was higher for 0.02 N. The reduction of nitrate was not sensitive to sulfate or chloride concentration in the ranges studied (0–2 and 1–1.5 mg/L, respectively), but the oxidation of ammonium was noticeably higher when chloride was present. Only small amounts of ammonium and nitrate remained in the second-stage effluent after coupled treatment.     

Pyrolysis of jute dust: effect of reaction parameters and analysis of products

Biowastes are becoming potential feedstocks for direct utilization or conversion to solid, liquid and gaseous fuels via various thermochemical routes. In this regard, jute dust which is a major agro-industrial waste in jute mills was pyrolysed in a fixed-bed reactor with an aim to study the product distribution and their characterization and to identify the optimum condition for bio-oil yield. The investigated process variables were temperature (400–700 °C), heating rate (10 and 40 °C/min) and nitrogen gas flow rate (50–250 ml/min). The yield of bio-oil is found to be maximum at 500 °C with a heating rate of 40 °C/min. However, further increase in temperature leads to decrease in bio-oil yield. Chemical compositions of the bio-oils were investigated using chromatographic and spectroscopic techniques such as ¹H NMR, FTIR and GC–MS. The heating value of the bio-oil is 26.71 MJ/kg. The study shows that jute dust have potential for conversion to bio-oil through the process of pyrolysis to supplement the petro-derived liquid fuel for heating and transportation applications after upgrading. The biochar produced as a co-product of jute dust pyrolysis can be a potential soil amendment with multiple benefits including increased soil fertility and C-sequestration.     

Adsorptive Removal of Malachite Green Chloride and Reactive Red-198 from Aqueous Solutions by Using Multiwall Carbon Nanotubes-Graft-Poly (2-acrylamido-2-methyl-1-propanesulfonic acid)

The multiwall carbon nanotubes (MWCNTs) were modified by 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) via grafting reaction and γ-rays of ⁶⁰Co source was used as initiator. The outcome product was called hydroxyethylated (HOEt-MWCNTs) graft poly(AMPS) and abbreviated as HOEt-MWCNTs-g-PAMPS. The parameters that affected the grafting yield were optimized. The maximum grafting obtained was ~20 %. HOEt-MWCNTs-g-PAMPS were characterized by Fourier transform infra red, scanning electron microscopy, high resolution transmission electron microscopy, thermal gravimetric analysis. The adsorptive removals of malachite green chloride (MGC) and reactive red 198 (RR-198) onto HOEt-MWCNTs-g-PAMPS were studied at variable conditions. The adsorption isotherms were analyzed using Langmuir, Redlich–Peterson, Freundlich, Khan and Sips models. The results referred that Sips model is the best fitting to adsorption of MGC and Freundlich model is the best fitting to RR-198 adsorption. The monolayer coverage capacities of HOEt-MWCNTs-g-PAMPS for MGC and RR-198 dyes were found 172 and 323 mg g^?1, respectively. The rate of kinetic adsorption processes of MGC and RR-198 onto HOEt-MWCNTs-g-PAMPS were described by using pseudo-first order, pseudo-second order and intraparticle diffusion models. The pseudo-first order and pseudo-second order models were the best choice among the kinetic models to depict the adsorption behaviors of MGC and RR-198 dyes onto HOEt-MWCNTs-g-PAMPS, respectively. Further, the effect of temperature on the adsorption isotherms was investigated and the thermodynamic parameters were obtained. The results indicated that the adsorption process is spontaneous and endothermic. The values of ΔG° varied in range with the mean values showing a gradual increase from ?3.17 to ?3.64 kJ mol^?1 for MGC and ?3.36 to ?3.73 kJ mol^?1 for RR-198. The reusability and regeneration of adsorbent were investigated. The outcome data referred to that the efficiency of adsorbent >98 %. The outline results declared that there is a good potentiality for the HOEt-MWCNTs-g-PAMPS to be used as an adsorbent for the removal of MGC and RR-198 from aqueous solutions.     

Preparation of MgCr<Subscript>2</Subscript>O<Subscript>4</Subscript> from waste tannery solution and effect of sulfate,chloride, and calcium on leachability of chromium

This paper presents a study regarding the preparation of MgCr₂O₄ from waste tannery solution, and chromium leaching behavior is also investigated with varying amounts of sulfate, chloride and calcium. The phase transformation, crystallinity index and crystallite diameter were characterized using XRD, FT-IR and thermal analysis. A well-crystallized MgCr₂O₄ was successfully prepared at 1400 °C. The sintering temperature had a major impact on the formation of MgCr₂O₄ compared with sintering time. The MgCr₂O₄ phase was observed initially at 400 °C and its crystallite diameter increased with increasing temperature. The concentration of total chromium leached and Cr(VI) decreased gradually with increasing temperature. The considerable amount of Cr(VI) was found in the leachate at 300–500 °C caused by Cr(VI) intermediary products. Sulfate and chlorine could impact the transformation efficiency of chromium adversely, and chlorine has a more significant effect than sulfate. The presence of calcium disturbed the formation of MgCr₂O₄ and new chromium species (CaCrO₄) appeared, which resulted in a sharp increase in the concentration of leached Cr(VI). Incorporating Cr(III) into the MgCr₂O₄ spinel for reusable products reduced its mobility significantly. This was demonstrated to be a promising strategy for the disposal of chromium containing waste resource.     

Kinetic Analysis of the Temperature Effect on Polyhydroxyalkanoate Production by <Emphasis Type="Italic">Haloferax mediterranei</Emphasis> in Synthetic Molasses Wastewater

Haloferax mediterranei is an extremely halophilic archaeon that is able to synthesize polyhydroxyalkanoate (PHA) in high salt environment with low sterility demand. In this study, a mathematical model was validated and calibrated for describing the kinetic behavior of H. mediterranei at 15, 20, 25, and 35 °C in synthetic molasses wastewater. Results showed that the production of PHA by H. mediterranei, ranging from 390 to 620 mg h^?1 L^?1, was strongly dependent on the temperature. The specific growth rate (µ _max), specific substrate utilization rate (q _max), and specific decay rate (k _d) of H. mediterranei increased with temperature following Arrhenius equation prediction. The estimated activation energy was 58.31, 25.59, and 22.38 kJ mol^?1 for the process of cell growth, substrate utilization, and cell decay of H. mediterranei, respectively. The high temperature triggered the increased PHA storage even without nitrogen limitation. Thus, working at high temperatures seems a good strategy for improving the PHA productivity of H. mediterranei.     

Adsorption of Ammonium by Graphene Oxide-Based Composites Prepared by UV Irradiation and Using as Slow-Release Fertilizer

A novel sodium alginate-grafted poly(acrylic acid)/graphene oxide (NaAlg-g-PAA/GO) composite hydrogel was prepared via ultraviolet irradiation, and characterized by infrared spectroscopy spectrometer. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. It was employed to adsorb NH₄⁺ from aqueous solution and used as slow-release nitrogen fertilizers (SNFs). Result indicated that the adsorption process for NH₄⁺ reached equilibrium within 50 min, with the adsorption capacity of 6.6 mmol g^?1 even if 30 wt% GO was incorporated. The results of adsorption kinetic and isotherm were well described by the pseudo-second-order and Freundlich model. The thermodynamics analysis showed the adsorption process was spontaneous. The study indicated excellent water-holding ratio of soil with 2 wt% SNFs was 81.2%, and nitrogen release was up to 55.1% within 40 days in soil. Overall, NaAlg-g-PAA/GO could be considered as an efficient adsorbent for the recovery of nitrogen with the agronomic reuse as a fertilizer.     

TSP,PM<Subscript>10</Subscript> and health risk assessment for heavy metals (Cr,Ni, Cu,Zn, Cd,Pb) in the ambience of the production line for waste cathode ray tube recycling

Recently, a typical semi-automatic recycling line is proved to be a feasible method for resource recovery of raw material of waste CRTs. However, there are no relevant studies about health risk assessment of the particles and heavy metals diffused from this physical recycling process for CRTs. In this study, TSP, PM₁₀ and heavy metals (Cr, Ni, Cu, Zn, Cd and Pb) in the ambience of the workshop have been evaluated. The mean concentrations of TSP and PM₁₀ in the workshop were 481.5 and 316.9 μg/m³, respectively. Meanwhile, it can be seen that Zn (8.1 and 7.9 μg/m³, respectively) was the most enriched metal in TSP and PM₁₀, followed by Pb (3.2 and 3.0 μg/m³, respectively). Health risk assessment showed that the total hazard index was 3.29, exceeding the danger threshold. The health risk of different metals was Cr > Cd > Ni. In short, the research results show that mechanical–physical process for e-waste recycling do exist the pollutant mission. So the effective measures should be taken to reduce the harm of pollutants on the workers’ health.     

Chitosan/Hydrophilic Plasticizer-Based Films: Preparation,Physicochemical and Antimicrobial Properties

The addition of plasticizers to biopolymer films is a good method for improving their physicochemical properties. The aim of this study was to evaluate the effect of chitosan (CHI) blended with two hydrophilic plasticizers glycerol (GLY) and sorbitol (SOR), at two concentrations (20 and 40 wt%) on their mechanical, thermal, barrier, structural, morphological and antimicrobial properties. The chitosan was prepared through the alkaline deacetylation of chitin obtained from fermented lactic from shrimp heads. The obtained chitosan had a degree of deacetylation (DA) of 84 ± 2.7 and a molecular weight of 136 kDa, which indicated that a good film had formed. The films composed of CHI and GLY (20 wt%) exhibited the best mechanical properties compared to the neat chitosan film. The percentage of elongation at break increase to over 700 % in the films that contained 40 % GLY, and these films also exhibited the highest values for the water vapor transmission rate (WVTR) of 79.6 ± 1.9 g m² h^?1 and a yellow color (b _o  = 17.9 ± 2.0) compared to the neat chitosan films (b _o  = 8.8 ± 0.8). For the structural properties, the Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analyses revealed an interaction in the acetamide group and changes in the crystallinity of plasticized films. The scanning electron micrographs revealed that all formulations of the chitosan films were smooth, and that they did not contain aggregations, pores or microphase separation. The thermal analysis using differential scanning calorimetry (DSC) revealed a glass transition temperature (Tg) of 130 °C for neat chitosan film, but the addition of SOR or GLY elicited a decrease in the temperature of the peak (120 °C). In addition, the antimicrobial activity of the chitosan films was evaluated against Listeria monocytogenes, and reached a reduction of 2 log after 24 h. The plasticizer concentration of 20 % GLY is sufficient for obtaining flexible chitosan films with good mechanical properties, and it could serve as an alternative as a packaging material to reduce environmental problems associated with synthetic packaging films.     

Sulfated Polysaccharides from Tunisian Fish Skins: Antioxidant,DNA Damage Protective Effect and Antihypertensive Activities

Sulfated polysaccharides were isolated from two Tunisian fish skins grey triggerfish (Balistes capriscus) (GTSP) and smooth hound (Mustelus mustelus) (SHSP). Their chemical and physical characteristics were investigated. The Analysis of surface morphology by scanning electron microscopy of both sulfated polysaccharides displayed the same shape with netted structure. The antioxidant activities of GTSP and SHSP were evaluated using various in vitro antioxidant assays: 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity, reducing power, β-carotene bleaching inhibition assay (IC_{50 GTSP} = 0.5 mg mL^?1 and IC_{50 SHSP} = 0.6 mg mL^?1) and DNA nicking assay. Both sulfated polysaccharides exhibited good antioxidant activities. The sulfated polysaccharides showed strong angiotensin I-converting enzyme inhibitory activities (IC_{50 GTSP} = 0.16 mg mL^?1 and IC_{50 SHSP} = 0.18 mg mL^?1). These results revealed that GTSP and SHSP exhibited significant antihypertensive activities. Overall, the results indicated that grey triggerfish and smooth hound skins can be used to generate high value-added products, thus offering a valuable source of bioactive sulfated polysaccharides for application in wide range of biotechnological applications.     

Design and first experimental results of a bubbling fluidized bed for air gasification of plastic waste

Plastic wastes have an especially high potential for use as alternative fuels, considering their high heating value and their large and stable availability. They could be used in electricity production based on gasification technologies, wherein electricity is produced in engines by means of the conversion of plastic wastes into a valuable gas. However, there are still some technical barriers to overcome before this technology can access the commercial stage, and further scientific research is needed to gain deeper understanding of the process and to be able to control and optimize it. This research presents the design and first experimental results of a bubbling fluidized bed gasifier conceived for the gasification of actual plastic residues. The experimental tests revealed that the selection and design of the reactor were adequate and proved some of the advantages of using plastic as a fuel, related in part to the absence of ashes and char. A valuable syngas over 5 MJ/m³ was generated, which contained a considerable fraction of methane as well as hydrogen and carbon monoxide as main combustible gases. The highest efficiency was achieved when the equivalence ratio was increased to 0.35, reaching 61 % in terms of cold gas efficiency and 66 % carbon conversion.