Remediation Of Industrial Wastewater Research Articles

Effective Removal of Cu(II) Ions from Aqueous Solution by Cross-Linked Chitosan-Based Hydrogels

The elimination of metal ions from industrial waste water is one of the most significant environmental needs. For the first time, two chitosan hydrogels that we had previously synthesized, cross-linked with varying concentrations of trimellitic anhydride isothiocyanate (represented by H1 and H2), were utilized in this investigation to adsorb Cu(II) ions. We found that pH 6, 25 °C, 200 mg L−1 of Cu(II) ions concentration, and 15 mg of hydrogel dosage were the ideal parameters for Cu(II) ion elimination. The kinetics of their adsorption fitted to the pseudo-second-order model with the highest correlation coefficient (R2) values equal to 0.999 and 1.00 for H1 and H2, respectively. The experimental qe values were found when H1 was equal to 97.59 mg g−1 (theoretical value is equal to 98.04 mg g−1) and H2 was equal to 96.20 mg g−1 (theoretical value is equal 99.01 mg g−1). The hydrogels achieved a removal effectiveness of 97.59% and their adsorption isotherms matched the Freundlich model, indicating the multi-layered and homogeneous adsorption nature. The removal of copper ions is significantly driven by the physisorption phenomenon. The hydrogels have a great possibility to be utilized as promising, efficacious, reusable adsorbents for industrial wastewater remediation. Thus, incorporation of a cross-linker, containing binding centers for Cu(II) ions, between chitosan chains is a good way to obtain suitable efficient adsorbents which are good choices for application in the field of metal elimination.

The complete chloroplast genome sequence of Lemna turionifera (Araceae)

Lemna turionifera is native to North America and northern Asia, with significant potential for industrial wastewater remediation. The complete nucleotide sequence of the L. turionifera chloroplast genome (cpDNA) was determined. The cpDNA is a circular molecule of 166,606 bp and containing a pair of inverted repeats (IRs) measuting 31,663 bp each. These IRs are flanked by a small single-copy region of 13,542 bp and a large single-copy region of 89,738 bp. The chloroplast genome of L. turionifera consisted of 112 unique genes, including 78 protein-encoding genes, 30 tRNA genes, and four rRNA genes. The phylogenetic analysis utilizing cpDNA provided a well-supported resolution of the relationships among subfamilies within the Araceae family. Our findings indicated a close relationship between L. turionifera and a clade consisting of L. minor, L. japonica, and L. gibba. The availability of the complete chloroplast genome sequence of L. turionifera presents valuable data for future phylogenetic investigations within the Lemnaceae family.

Degradation of organic Pollutant by Using of BiVO4-NiFe2O4 Heterostructure Photocatalyst under Visible Light Irradiation: Assessment of Detoxicity Study Using Cirrhinus mrigala.

The current study mainly concentrates on the photocatalytic activity of composite nanomaterial of BiVO4 (BVO), NiFe2O4 (NFO), and BiVO4-NiFe2O4 (BVO-NFO) under visible light. Among these, BVO-NFO composite degrades crystal violet dye within 60 min with a percentage degradation of 95.65% under visible light illumination. The BVO-NFO composite exhibits better photodegradation performance, which can be attributed to the effective light absorption and reduced recombination of the photoexcited charge carriers. Additionally, by applying a magnetic field, the BVO-NFO composite can be magnetically recovered by using the magnet for subsequent recycling. The synthesized composite was characterized using optical techniques like X-ray diffraction, ultraviolet diffuse reflectance spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, and energy dispersive X-ray analysis. The effect of dye, before and after degradation, on vital organs of fish species was examined such as fish gill (pulmonary-toxicity), fish liver (hepato-toxicity), fish kidney (renal toxicity), fish brain (neural toxicity), and fish muscle (myopathy). This work offers a clear and practical method for designing a highly crystalline semiconductor photocatalyst for dye degradation and the remediation of industrial wastewater.

A Cost-Effective Hemin-Based Artificial Enzyme Allows for Practical Applications.

Nanomaterials excel in mimicking the structure and function of natural enzymes while being far more interesting in terms of structural stability, functional versatility, recyclability, and large-scale preparation. Herein, the story assembles hemin, histidine analogs, and G-quadruplex DNA in a catalytically competent supramolecular assembly referred to as assembly-activated hemin enzyme (AA-heminzyme). The catalytic properties of AA-heminzyme are investigated both in silico (by molecular docking and quantum chemical calculations) and in vitro (notably through a systematic comparison with its natural counterpart horseradish peroxidase, HRP). It is found that this artificial system is not only as efficient as HRP to oxidize various substrates (with a turnover number kcat of 115 s-1) but also more practically convenient (displaying better thermal stability, recoverability, and editability) and more economically viable, with a catalytic cost amounting to <10% of that of HRP. The strategic interest of AA-heminzyme is further demonstrated for both industrial wastewater remediation and biomarker detection (notably glutathione, for which the cost is decreased by 98% as compared to commercial kits).

Bacterial and microalgal co-fixation for remediation of industrial wastewater contaminated with arsenic, mercury, and other pollutants

Microbial remediation is an efficient approach for improving heavy metal-contaminated water environments. Herein, this article developed a composite bacterial agent (CBA) with a high heavy metal tolerance. Within 12 h, the CBA demonstrated removal efficiencies of 65.18 ± 1.53% for As and 60.73 ± 0.94% for Hg in wastewater. This study prepared bacterial–algal fixed spheres (BAFS) to further enhance the removal efficiencies of As and Hg. Moreover, during desorption using 0.1 mol/L HNO3 for 60 min, the BAFS maintained high removal efficiencies for As and Hg after five adsorption–desorption cycles. Applying BAFS to industrial wastewater collected from factory outfall caused substantial reductions in chemical pollutants and other heavy metals. Scanning electron microscopy analysis further revealed that the internal cavities formed through the crosslinking of immobilized materials provided excellent survival carriers for bacteria and microalgae. Infrared spectroscopy analysis demonstrated the involvement of three functional groups, namely -OH, -CH2-, and C-O-C, in pollutant adsorption. Additionally, microbial community diversity analysis indicated that immobilization effectively preserved the pollutant adsorption ability of the microorganisms, increasing the abundance of functional microbial populations. These characteristics improved the efficiency of industrial wastewater treatment while promoting recycling.

Cellulose-Based Hydrogels for Wastewater Treatment: A Focus on Metal Ions Removal.

The rapid worldwide industrial growth in recent years has made water contamination by heavy metals a problem that requires an immediate solution. Several strategies have been proposed for the decontamination of wastewater in terms of heavy metal ions. Among these, methods utilizing adsorbent materials are preferred due to their cost-effectiveness, simplicity, effectiveness, and scalability for treating large volumes of contaminated water. In this context, heavy metal removal by hydrogels based on naturally occurring polymers is an attractive approach for industrial wastewater remediation as they offer significant advantages, such as an optimal safety profile, good biodegradability, and simple and low-cost procedures for their preparation. Hydrogels have the ability to absorb significant volumes of water, allowing for the effective removal of the dissolved pollutants. Furthermore, they can undergo surface chemical modifications which can further improve their ability to retain different environmental pollutants. This review aims to summarize recent advances in the application of hydrogels in the treatment of heavy metal-contaminated wastewater, particularly focusing on hydrogels based on cellulose and cellulose derivatives. The reported studies highlight how the adsorption properties of these materials can be widely modified, with a wide range of adsorption capacity for different heavy metal ions varying between 2.3 and 2240 mg/g. The possibility of developing new hydrogels with improved sorption performances is also discussed in the review, with the aim of improving their effective application in real scenarios, indicating future directions in the field.

Cotton-derived three-dimensional carbon fiber aerogel with hollow nanocapsules and ultrahigh adsorption efficiency in dynamic sewage treatment system

An ultralight 3D carbon fiber aerogel with good flexibility is developed via soaking cotton in water and then calcinating at a high temperature. This cotton-derived carbon material is constituted by amorphous carbon and retains slight oxygen-containing groups. Besides, a lot of hollow carbon nanocapsules are yielded on the inside surface, resulting in abundant micropores and mesopores. Systemic investigations explore the molecular transformation from cotton to carbon fiber, and the formation of carbon nanocapsules. In the adsorption process for methyl orange (MO), this carbon fiber aerogel exhibits both a rapid adsorption rate and the ultrahigh adsorbability of 862.9 mg/g, outclassing most of carbon materials reported. Therefore, a dynamic sewage treatment system is built and consecutively removes hydrosoluble pollution for a long-term running time. For the cotton-derived carbon fiber aerogel, the good mechanical flexibility, excellent adsorption property, and high stability jointly provide a vast application prospect in future industrial wastewater remediation.

Bioremediation of Metal-Polluted Industrial Wastewater with Algal-Bacterial Consortia: A Sustainable Strategy

Aquatic pollution is a burning issue nowadays due to urbanization and industrialization. Industrial wastewater (IWW) contains pollutants that pose a great risk to the environment and human beings and is a big challenge for industries. The remediation of IWW by microorganisms is an environmentally friendly technique. This study was carried out to evaluate the pollution of IWW and to use consortia of Bacillus pakistanensis, Lysinibacillus composti, and Cladophora glomerata for bioremediation. The IWW was obtained from the Hayatabad Industrial Estate and was evaluated for physicochemical parameters and metal concentration. A pot experiment was carried out for two weeks to assess the efficiency of the developed consortia. The IWW and tap water (control) were treated with three different consortia (Bacillus pakistanensis-Cladophora glomerata (CT1, E1), Lysinibacillus composti-Cladophora glomerata (CT2, E2), and Bacillus pakistanensis-Lysinibacillus composti-Cladophora glomerata (CT3, E3). The three pots (CT1, CT2, and CT3) serving as the control were provided with tap water, and the three experimental pots (E1, E2, and E3) were provided with IWW. After treatment, substantial reductions were obtained in the following parameters and percentages: colour 85.7%, electrical conductivity (EC) 40.8%, turbidity 69.6%, sulphide 78.5%, fluoride 38.8%, chloride 62.9%, biological oxygen demand (BOD) 66%, chemical oxygen demand (COD) 81.8%, total suspended solids (TSSs) 82.7%, total dissolved solids (TDSs) 24.6%, Ca hardness 37.2%, Mg hardness 50%, and total hardness 39%. The samples of water were also examined for metal concentrations using atomic absorption spectrophotometry. The selected species removed 98.2% of Mn, 94% of Cu, 97.7% of Cr, 91.6% of Cd, 92.8% of Co, 79.6% of Ag, 82.6% of Ni, 98% of Ca, 90% of Mg, and 82.1% of Pb. The BCF values showed by the consortia for Mn, Cu, Cr, Cd, Co, Ag, Ni, Ca, Mg, and Pb were 91.8, 67, 97.5, 83.3, 85.7, 48.1, 80.4, 84.3, 82.5, and 80.3%, respectively. The t-test analysis showed that the treatment with the selected species significantly decreased the metal concentrations in the IWW (p ≤ 0.05). Overall, the study concludes that metal concentration in the water was decreased significantly by the consortia of algae-bacteria.

Micro-/nano- bubbles ozonation for effective industrial wastewater remediation: From lab to pilot-scale application

Herein, micro-nano bubbles (MNBs) assisted ozonation process (O3/MNBs) was developed to enhance interfacial reactions for pollutant degradation. Notably, the removal of organic contaminants in O3/MNBs system was ultrafast over a wide pH range, much faster than that of macrobubbles ozonation process (O3/MaBs). Experimental observations suggested that MNBs can effectively accelerate O3 interfacial mass transfer and enrich abundant OH− from a bulk solution, thus inducing high concentrations of O3 and hyperaccumulation of OH− ions at gas-liquid interface. These interfacial characteristics of MNBs resulted in formation of a special interfacial reaction field, in which high concentration of O3 can be quickly activated by hyperaccumulated OH− ions along with assistance of energy released by MNBs collapse, ultimately boosting •OOH generation significantly. In addition, •OOH/•O2- performed as critical intermediates for the formation of •OH in O3/MNBs process. O3/MNBs system demonstrated favorable and steady performance during long-term advanced treatment of industrial wastewater (∼7 m3/h) with significantly lower ΔO3/ΔCOD (1.41) than O3/MaBs system (2.69). The pilot-scale demonstration of O3/MNBs efficiently degraded all four categories of organic contaminants according to EEM fluorescence spectra. The study demonstrated an environmentally-benign technology for effective treatment of industrial wastewater.

Robust, magnetic, and effective Pd-based nanocatalyst for reduction of toxic hexavalent chromium and nitrophenols

A serial of magnetic and robust nanocatalysts of Pd nanoparticles with a mean size of 4 nm evenly supported on N-doped porous carbon with Co wrapped (Co-NC) were fabricated by a facile route at room temperature. Among these, 18 %Pd/Co-NC has regular morphology and exhibits the highest activity towards reduction of Cr (VI) with HCOOH and nitrophenols with NaBH4 in aqueous solution. What is more, 18 %Pd/Co-NC has a higher catalytic activity than that of 20 % commercial Pd/C towards the reduction of Cr(VI). The excellent performance may be due to the Pd nanoparticles of small size, uniform dispersion on Co-NC, large BET surface area, abundant active sites, nitrogen doping, and synergetic effect between Pd and the support of Co-NC. The introduction of Co nanoparticles to the support not only provides magnetism but also may prevent the oxidation of Pd, thus facilitating the separation of the catalyst from the solution and providing more active Pd species to catalyze the reduction reaction. The catalyst can be separated easily by an external magnet and remain the activity without obvious decline after the recycling experiment, indicating the catalyst has a good stability in acidic or basic solution. What is more, K2Cr2O7 can be catalytically reduced by Pd/Co-NC in an industrial environment, confirming the catalyst has a potential application in the remediation of industrial wastewater.

Facile synthesis and physicochemical characterization of κ-Carrageenan-silver-bentonite based nanocatalytic platform for efficient degradation of anionic azo dyes

Water pollution due to textile industry effluents is a global concern that warrants versatile research solutions for degrading them, and for a sustainable environment. In the present work, by using the imperative role of nanotechnology, a facile one-pot synthesis has been devised to generate κ-carrageenan capped silver nanocatalyst (CSNC), and was immobilized on 2D bentonite (BT) sheets to generate nanocatalytic platform (BTCSNC) for the degradation of anionic azo dyes. The nanocomposite(s) were physicochemically characterized using UV–Vis, DLS, TEM, FESEM, PXRD, ATR-FTIR, TGA, BET and XPS etc., to obtain insights into the nanocomposite composition, structure, stability, morphology and mechanism of interaction. The obtained CNSC are monodispersed, spherical with a size of 4 ± 2 nm, and were stabilized by the functional groups (-OH, COO‾, and SO3‾) of κ-Crg. The broadening of peak corresponding to basal plane (001) of BT montmorillonite in PXRD spectra established its exfoliation upon addition of CSNC. XPS and ATR-FTIR data evidenced the absence of covalent interactions between CSNC and BT. The catalytic efficiency of CSNC and BTCSNC composites were compared for the degradation of methyl orange (MO) and congo red (CR). The reaction followed a pseudo first order kinetics, and immobilization of CSNC on BT resulted in a 3–4 fold enhancement in degradation rates. The rates achieved for the degradation kinetics are: MO degradation within 14 s (Ka 9.86 ± 2.00 min−1), and CR degradation within 120 s (Ka of 1.24 ± 0.13 min−1). Further, a degradation mechanism has been proposed by analyzing the products identified through LC-MS. The reusability studies of the BTCSNC evidenced the complete activity of the nanocatalytic platform for six cycles, and gravitational separation method for catalyst recycling. In a nutshell, the current study provided an environmentally friendly, sizable, and sustainable nano catalytic platform” for the remediation of industrial wastewater contaminated with hazardous azo dyes”.

Bioremediation of Heavy Metals from Industrial Effluents Using Bacillus pakistanensis and Lysinibacillus composti

Aquatic pollution is one of the main problems due to rapid development in industrialization. The remediation of industrial wastewater (IWW) by microorganisms is an environmentally friendly technique. This study was conducted to assess pollution load in IWW and to use Bacillus pakistanensis and Lysinibacillus composti individually and in a consortium for bioremediation. The IWW was obtained from Hayatabad Industrial Estate and evaluated for physicochemical parameters and metal concentration. The pH, color, electrical conductivity (EC), turbidity, temperature, sulfide, fluoride, chloride, biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total dissolved solids (TDS), calcium hardness, magnesium hardness, and total hardness were noted as 6.82, 440 TCU, 1.195 mS/cm, 54.65 mg/L, 26.8 °C, 5.60 mg/L, 3.6 mg/L, 162 mg/L, 85.5 mg/L, 921 mg/L, 232 mg/L, 794 mg/L, 590 mg/L, 395 mg/L, and 985 mg/L, respectively. The metals such as manganese, copper, chromium, cadmium, cobalt, silver, nickel, calcium, magnesium, and lead were also analyzed as 1.23 mg/L, 0.81 mg/L, 2.12 mg/L, 0.18 mg/L, 0.151 mg/L, 0.24 mg/L, 1.12 mg/L, 0.113 mg/L, 14.5 mg/L, and 0.19 mg/L, respectively. A pot experiment was performed for two weeks to evaluate the efficiency of the selected species. The IWW and tap water (control) were treated with selected species, individually and in a consortium. After treatment, a considerable reduction was noted in the color 87.3%, EC 46.5%, turbidity 84.1%, sulfide 87.5%, fluoride 25.0%, chloride 91.3%, BOD 96.4%, COD 86.5%, TSS 90%, TDS 45.0%, Ca hardness 42.3%, Mg hardness 77.2%, and total hardness 52.2%. After the experiment, samples of water were also analyzed for metal concentrations by atomic absorption spectrophotometry. The selected species removed 99.3% of Mn, 99.6% of Cu, 97.8% of Cr, 94.4% of Cd, 46.3% of Co, 85.1% of Ag, 88.4% of Ni, 98.8% of Ca, 91.5% of Mg, and 90.5% of Pb. The t-test analysis showed that the treatment with the selected species significantly decreased the metal concentrations in the IWW (p ≤ 0.05).

Chemically cross-linked keratin and nanochitosan based sorbents for heavy metals remediation

Biosorbents for water remediation were prepared using keratin biopolymer cross-linked with nanochitosan (NC). Keratin proteins were dissolved using reducing agents and NC was incorporated with concentrations of 1, 3 and 5 % individually into the keratin solution. The mixtures were thermally treated at 75°C overnight, which promoted the formation of ester bonds between the hydroxyl groups of nanochitosan and the carboxylic groups of the keratin biopolymer. The resulting keratin derived biosorbents were characterized by X-Ray photoelectron spectroscopy, confirming the cross-linking between keratin and nanochitosan. The chicken feathers keratin (CFK) surface modifications with nanochitosan were examined with Brunauer-Emmett-Teller, scanning and transmission electron microscopies. The sorption capacity of biosorbents was tested for eight different metals simultaneously at different contact times (15, 30, 60, 120, 240, 280 mins) and pH (5.5, 7.5 and 8.5), including arsenic, selenium, chromium, nickel, cobalt, lead, cadmium and zinc, using simulated industrial wastewater water containing 600 μgl−1 concentration of each metal. The synthesized environmentally benign biosorbents exhibited biosorption of metals upto 98 % at pH 7.5 and a contact time of 24 h, showing their potential for industrial wastewater remediation.

Preparation and Characterization of a New Bis-Uracil Chitosan-Based Hydrogel as Efficient Adsorbent for Removal of Anionic Congo Red Dye

A new hydrogel, based on chitosan crosslinked with 2-chlorophenyl-bis(6-amino-1,3-dimethyluracil-5-yl) methane, (2Clph-BU-Cs), has been successfully created. Various instrumental techniques such as elemental analysis, FTIR, SEM, and XRD were used to prove its structure. Its removal efficiency for anionic Congo red (CR) dye under different conditions for industrial wastewater treatment was studied. For optimizing the conditions to maximize CR dye removal, the impacts of temperature, contact time, pH, and initial concentration of the dye on adsorption capacity were investigated. The removal of the dye was pH-dependent, with a much higher value achieved at pH 4 than at pH 7 and 9. The maximum adsorption capacity of the hydrogel was 93.46 mg g-1. The model of adsorption process was fitted to the pseudo-second-order kinetic model. The intraparticle diffusion demonstrated the multi-step nature of the adsorption process. The thermodynamic results showed that the adsorption process was endothermic because of the positive value of enthalpy (43.70 kJ mol-1). The process of adsorption at high temperatures was spontaneous, according to the values of ∆G0. An increase in randomness was seen in the value of ∆S°. Generally, the investigated hydrogel has the potential to be used as a promising effective reusable adsorbent for industrial wastewater remediation.

Catalytic effects of molybdate and chromate–molybdate films deposited on platinum for efficient hydrogen evolution

AbstractBACKGROUNDSodium chlorate (NaClO3) is extensively used in the paper industry, but its production uses strictly regulated highly toxic Na2Cr2O7 to reach high hydrogen evolution reaction (HER) Faradaic efficiencies. It is therefore important to find alternatives either to replace Na2Cr2O7 or reduce its concentration.RESULTSThe Na2Cr2O7 concentration can be significantly reduced by using Na2MoO4 as an electrolyte co‐additive. Na2MoO4 in the millimolar range shifts the platinum cathode potential to less negative values due to an activating effect of cathodically deposited Mo species. It also acts as a stabilizer of the electrodeposited chromium hydroxide but has a minor effect on the HER Faradaic efficiency. X‐ray photoelectron spectroscopy (XPS) results show cathodic deposition of molybdenum of different oxidation states, depending on deposition conditions. Once Na2Cr2O7 was present, molybdenum was not detected by XPS, as it is likely that only trace levels were deposited. Using electrochemical measurements and mass spectrometry we quantitatively monitored H2 and O2 production rates. The results indicate that 3 μmol L−1 Na2Cr2O7 (contrary to current industrial 10–30 mmol L−1) is sufficient to enhance the HER Faradaic efficiency on platinum by 15%, and by co‐adding 10 mmol L−1 Na2MoO4 the cathode is activated while avoiding detrimental O2 generation from chemical and electrochemical reactions. Higher concentrations of Na2MoO4 led to increased oxygen production.CONCLUSIONCareful tuning of the molybdate concentration can enhance performance of the chlorate process using chromate in the micromolar range. These insights could be also exploited in the efficient hydrogen generation by photocatalytic water splitting and in the remediation of industrial wastewater. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley &amp; Sons Ltd on behalf of Society of Chemical Industry (SCI).

Nano-sphere RuO2 embedded in MOF-derived carbon arrays as a dual-matrix anode for cost-effective electrochemical wastewater treatment

The electrodes' activity, surface area and cost hinder the deployment of electrochemical wastewater treatment. Using an economical microfiber-based carbon felt (CF) substrate, we design RuO2 nanospheres confined by CoxO cooperated carbon nanoarrays (RuO2-CoxO@TCF) to augment noble metal utilization and thus reduce the catalyst cost. RuO2-CoxO@TCF anode with vertical diffusion channels exhibits rapid generation ability of oxidizing species particularity in the presence of Cl− ions, which play a crucial role in azo bond cleavage and benzene ring chlorination of methyl orange. As a result, the catalyst shows 99.5 % color removal and ∼ 70 % mineralization efficiency at a concentration of 60 ppm. In synthetic dyeing wastewater, RuO2-CoxO@TCF delivers a stable total organic carbon (TOC) removal throughout ten cycling tests. Moreover, the electricity consumption of RuO2-CoxO@TCF is far below the reference anode, showing great promise for dye degradation and remediation of industrial wastewater.

Photocatalytic Performance of Organically Templated Cr-Doped Co3O4 in Remediation of Industrial Wastewater: Effect of Order–Disorder in the Lattice

In photocatalysis, the optical properties and surface parameters significantly affect the catalytic performance. To engineer the optical properties and textural structure, Cr and p-phenylene diamine (PDA) were utilized as dopant and textural structure regulator, respectively. A series of Cr-doped Co3O4 with dopant percentages of 0, 1, 3, and 5, templated PDA at a fixed ratio of 5%, and another un-templated sample with a dopant ratio of 5% were prepared. The co-precipitation method was applied in swift and innovative procedures, where a calculated amount of NaOH was used as a precipitant. The optical properties, dopant concentration quenching, and surface parameters are strongly affected by the order–disorder in the lattice and dopant concentration. The lattice regularity affects the optical properties and the surface parameters along with the dopant concentration. The photocatalysts were evaluated in the disposal of organic pollutants in a representative sample of wastewater collected from different industrial activities. The function of another function was applied to monitor the pollutants' disposal, taking the total organic carbon (TOC) as a function of the pollutants' concentration and the photometric absorbance as a function of the TOC. The kinetic investigation exhibited the significant role of the pore system on the reaction rate.

In Situ Ring-Opening Polymerization of L-lactide on the Surface of Pristine and Aminated Silica: Synthesis and Metal Ions Extraction.

The development of functional materials from food waste sources and minerals is currently of high importance. In the present work, polylactic acid (PLA)/silica composites were prepared by in situ ring-opening polymerizations of L-lactide onto the surface of pristine (Silochrom) and amine-functionalized (Silochrom-NH2) silica. The characteristics of the ring-opening polymerization onto the surface of modified and unmodified silica were identified and discussed. Fourier transform infrared spectroscopy was used to confirm the polymerization of lactide onto the silica surface, and thermogravimetric analysis determined that PLA constituted 5.9% and 7.5% of the composite mass for Silochrom/PLA and Silochrom-NH2/PLA, respectively. The sorption properties of the composites with respect to Pb(II), Co(II), and Cu(II) ions were investigated, and the effect of contact time, initial metal ion concentration, and initial pH were evaluated. Silochrom-NH2/PLA composites were found to have a higher adsorption capacity than Silochrom/PLA for all chosen ions, with the highest adsorption value occurring for Pb2+ at 1.5 mmol/g (90% removal efficiency). The composites showed the highest performance in the neutral or near-neutral pH (created by distilled water or buffer pH 6.86) during the first 15 min of phase contact. The equilibrium characteristics of adsorption were found to follow the Langmuir isotherm model rather than the Freundlich and Temkin models. Perspective applications for these PLA/silicas include remediation of industrial wastewater or leaching solutions from spent lead-acid and Li-ion batteries.

In Situ Synthesis of Zero-Valent Iron-Decorated Lignite Carbon for Aqueous Heavy Metal Remediation

Lignite’s large abundance, physicochemical properties and low cost are attractive for industrial wastewater remediation. However, directly applying lignite for wastewater treatment suffers low efficiency. Here, we synthesize highly efficient zero-valent iron (ZVI)-decorated lignite carbon through the in-situ carbonization of a lignite and FeCl2 mixture for heavy metal removal. The effect of carbonization temperature on the morphology, structure and crystallite phases of ZVI-decorated lignite carbons (ZVI-LXs) was investigated. At an optimized temperature (i.e., 1000 °C), ZVI particles were found evenly distributed on the lignite matrix with the particles between 20 to 190 nm. Moreover, ZVI particles were protected by a graphene shell that was formed in situ during the carbonization. The synthesized ZVI-L1000 exhibited higher Cu2+, Pb2+ and Cd2+ stripping capacities than pristine lignite in a wide pH range of 2.2–6.3 due to the surface-deposited ZVI particles. The maximum Langmuir adsorption capacities of ZVI-L1000 for Cd2+, Pb2+ and Cu2+ were 38.3, 55.2 and 42.5 mg/g at 25 °C, respectively, which were 7.8, 4.5 and 10.6 times greater than that of pristine lignite, respectively. ZVI-L1000 also exhibited a fast metal removal speed (~15 min), which is ideal for industrial wastewater treatment. The pseudo-second-order model fits well with all three adsorptions, indicating that chemical forces control their rate-limiting adsorption steps. The reduction mechanisms of ZVI-L1000 for heavy metals include reduction, precipitation and complexation.

Unique Chemistry and Structure of Pyrolyzed Bovine Bone for Enhanced Aqueous Metals Adsorption

Bone waste is a problematic slaughterhouse waste typically disposed of in landfills. The pyrolyzed product of this waste shows strong potential in mine and industrial waste water remediation and work is needed to identify chemical and structural parameters which drive performance. Diffuse Reflectance Fourier Transform Spectroscopy (DRIFTS) was used to probe carbonate (CO32−), phosphate (PO43−) and hydroxyl (OH−) environments of mineral phases and functional group chemistry in carbonaceous phase, revealing a potentially synergistic functionality between the two in bone char. CO32− and water substitutions in the mineral lattice were found to persist after pyrolysis to 750 °C, and more soluble non-apatite calcium phosphate phases were observed using second derivative analysis of the v3 PO43− band. Nitrogen-rich functional groups were found in the carbonaceous phase which are associated with complexation of aqueous metals, and ordered aromatic clusters identified by Raman spectroscopy indicate a porous carbon skeletal structure to promote metals adsorption and complexation. These results point to unique chemical and structural features of bone char which are not easily replicated by synthetic carbonated apatite or activated carbon and which contribute to the excellent aqueous metals removal power of bone char.Graphical