Synthesis and evaluation of a novel cross-linked biochar/ferric chloride hybrid material for integrated coagulation and adsorption of turbidity and humic acid from synthetic wastewater: Implications for sludge valorisation.

The deep removal of organic pollutants is challenging for coagulation technology in drinking water and wastewater treatment plants to satisfy the rising water standards. Iron (III) chloride (FeCl3) is a popular inorganic coagulant; although it has good performance in removing the turbidity (TB) in water at an alkaline medium, it cannot remove dissolved pollutants and natural organic matter such as humic acid water solution. Additionally, its hygroscopic nature complicates determining the optimal dosage for effective coagulation. Biochar (BC), a popular adsorbent with abundant functional groups, porous structure, and relatively high surface area, can adsorb adsorbates from water matrices. Therefore, combining BC with FeCl3 presents a potential solution to address the challenges associated with iron chloride. Consequently, this study focused on preparing and characterizing a novel biochar/ferric chloride-based coagulant (BC-FeCl3) for efficient removal of turbidity (TB) and natural organic matter, specifically humic acid (HA), from synthetic wastewater. The potential solution for the disposal of produced sludge was achieved by its recovering and recycling, then used in adsorption of HA from aqueous solution. The novel coagulant presented high TB and HA removal within 10 min of settling period at pH solution of 7.5. Furthermore, the recovered sludge presented a good performance in the adsorption of HA from aqueous solution. Adsorption isotherm and kinetics studies revealed that the Pseudo-second-order model best described kinetic adsorption, while the Freundlich model dominated the adsorption isotherm.

Remediation of soil polluted with Pb and Cd and alleviation of oxidative stress in Brassica rapa plant using nanoscale zerovalent iron supported with coconut-husk biochar.

Accumulation of toxic elements by plants from polluted soil can induce the excessive formation of reactive oxygen species (ROS), thereby causing retarded plants' physiological attributes. Several researchers have remediated soil using various forms of zerovalent iron; however, their residual impacts on oxidative stress indicators and health risks in leafy vegetables have not yet been investigated. In this research, nanoscale zerovalent iron supported with coconut-husk biochar (nZVI-CHB) was synthesized through carbothermal reduction process using Fe2O3 and coconut-husk. The stabilization effects of varying concentrations of nZVI-CHB and CHB (250 and 500 mg/kg) on cadmium (Cd) and lead (Pb) in soil were analyzed, and their effects on toxic metals induced oxidative stress, physiological properties, and antioxidant defence systems of the Brassica rapa plant were also checked. The results revealed that the immobilization of Pb and Cd in soil treated with CHB was low, leading to a higher accumulation of metals in plants grown. However, nZVI-CHB could significantly immobilize Pb (57.5-62.12%) and Cd (64.1-75.9%) in the soil, leading to their lower accumulation in plants below recommended safe limits and eventually reduced carcinogenic risk (CR) and hazard quotient (HQ) for both Pb and Cd in children and adults below the recommended tolerable range of <1 for HQ and 10-6 - 10-4 for CR. Also, a low dose of nZVI-CHB significantly mitigated toxic metal-induced oxidative stress in the vegetable plant by inhibiting the toxic metals uptake and increasing antioxidant enzyme activities. Thus, this study provided another insightful way of converting environmental wastes to sustainable adsorbents for soil remediation and proved that a low-dose of nZVI-CHB can effectively improve soil quality, plant physiological attributes and reduce the toxic metals exposure health risk below the tolerable range.

Fabrication of a SnO2-Sb electrode with TiO2 nanotube array as the middle layer for efficient electrochemical oxidation of amaranth dye.

Efficient, stable, and easily producible electrodes are useful for treating dye wastewater through electrochemical oxidation. In this study, an Sb-doped SnO2 electrode with TiO2 nanotubes as the middle layer (TiO2-NTs/SnO2-Sb) was prepared through an optimized electrodeposition process. Analyses of the coating morphology, crystal structure, chemical state, and electrochemical properties revealed that tightly packed TiO2 clusters provided a larger surface area and more contact points, which is conducive to reinforcing the binding of SnO2-Sb coatings. Compared with a Ti/SnO2-Sb electrode without a TiO2-NT interlayer, the catalytic activity and stability of the TiO2-NTs/SnO2-Sb electrode significantly improved (P < 0.05), as reflected by the 21.8% increase in the amaranth dye decolorization efficiency and 200% increase in the service life. The effects of current density, pH, electrolyte concentration, initial amaranth concentration, and the interaction between various combinations of parameters on the electrolysis performance were investigated. Based on response surface optimization, the maximum decolorization efficiency of the amaranth dye could reach 96.2% within 120 min under the following set of optimized parameter values: 50 mg L-1 amaranth concentration, 20 mA cm-2 current density, and 5.0 pH. A potential degradation mechanism of the amaranth dye was proposed based on the experimental results of a quenching test, ultraviolet-visible spectroscopy, and high-performance liquid chromatography-mass spectrometry. This study provides a more sustainable method for fabricating SnO2-Sb electrodes with TiO2-NT interlayers to treat refractory dye wastewater.

Application of KHSO5 for remediation of soils polluted by organochlorides: A comprehensive study on the treatment's efficacy, environmental implications, and phytotoxicity.

Soil pollution caused by complex organochloride mixtures has been increasing in many parts of the world in recent years; as a result, countless numbers of people are exposed to dangerous pollutions; hence, the treatment of organochlorides-polluted soils is gaining considerable attention. In this study, the potential of unactivated peroxymonosulfate (KHSO5) in remediating soil co-contaminated with trichlorophenol, para-dichlorobenzene, and para-chloro-meta-cresol was investigated. In addition, the treatment's collateral effect on critical soil properties was explored. The result revealed that treating 10 g of soil with 20 mL of 5 mM KHSO5 for 60 min could oxidize 70.49% of the total pollutants. The pH of the soil was decreased following the treatment. The significant decrease, (p < 0.05), in the soil organic matter following the remediation has affected cation exchange capacity, and available nitrogen. It was also observed that the treatment reduced the ß-glucosidase, urease, invertase, and cellulase activities significantly, (p < 0.05). The treatment, on the other hand, brought negligible effects on available phosphorus, available potassium, and particle size distribution. The phytotoxicity tests, which included seed germination and root elongation and soil respiration tests revealed that the treatment did not leach toxins into the treated soil. The treatment method was found to be relatively ecofriendly and cost effective.

Environmental opportunities and challenges of utilizing unactivated calcium peroxide to treat soils co-contaminated with mixed chlorinated organic compounds.

Calcium peroxide (CaO2) has been proven to oxidize various organic pollutants when they exist as a single class of compounds. However, there is a lack of research on the potential of unactivated CaO2 to treat mixed chlorinated organic pollutants in soils. This study examined the potential of CaO2 in treating soils co-contaminated with p-dichlorobenzene (p-DCB) and p-chloromethane cresol (PCMC). The effects of CaO2 dosage and treatment duration on the rate of degradation were investigated. Furthermore, the collateral effects of the treatment on treated soil characteristics were studied. The result showed that unactivated CaO2 could oxidize mixed chlorinated organic compounds in wet soils. More than 69% of the pollutants in the wet soil were mineralized following 21 days of treatment with 3% (w/w) CaO2. The hydroxyl radicals played a significant role in the degradation process among the other decomposition products of hydrogen peroxide. Following the oxidation process, the treated soil pH was increased due to the formation of calcium hydroxide. Soil organic matter, cation exchange capacity, soil organic carbon, total nitrogen, and certain soil enzyme activities of the treated soil were decreased. However, the collateral effects of the system on electrical conductivity, available phosphorus, and particle size distribution of the treated soil were not significant. Likewise, since no significant release of heavy metals was seen in the treated soil matrix, the likelihood of metal ions as co-pollutants after treatment was low. Therefore, CaO2 can be a better alternative for treating industrial sites co-contaminated with chlorinated organic compounds.

Remediation of trichloroethylene contaminated soil by unactivated peroxymonosulfate: Implication on selected soil characteristics.

The advanced oxidation process (AOP) based on activated Peroxymonosulfate (PMS) has been attracting many people in the field of soil and water remediation in many ways while ignoring the shortcomings. The high cost of activators, and energy input, as well as the expense to separate the catalyst and transition metal reducing agent from the treated soil, were some disadvantages of using activated PMS. Based on the above rationales of problems related to the use of activated PMS, this study aimed to study the performance of using unactivated peroxymonosulfate for the advanced oxidation process to remediate soil contaminated by trichloroethylene (TCE), and to evaluate the synergistic effect on selected soil properties after treatment. The results showed that within 45 min, a single injection of 5 mM PMS at its initial pH value can degrade 86.90% of the total TCE in the soil. However, when PMS was continuously injected, the removal rate was increased to 95.25%. The direct reaction of TCE and PMS was the main cause of degradation. PMS can degrade TCE in a wide pH range (pH 3-11), but the maximum degradation was at pH = 2.9 (the initial pH of PMS). After the treatment, the soil organic matter (SOM) was degraded significantly. In contrast, FTIR, SEM, and hydrometer tests conducted on the soil showed that the treatment had no significant effect on the functional groups and particle size distribution of the treated soil. The study on the effect of the treatment on the concentration of bioavailable heavy metals in the treated soil showed that only manganese and copper metals were significantly increased after the treatment. According to the results obtained in this study, it is more beneficial and feasible to use unactivated peroxymonosulfate in the advanced oxidation process when remediating soil contaminated by chlorinated organic matter.

Effect of lignin and plant growth-promoting bacteria (Staphylococcus pasteuri) on microbe-plant Co-remediation: A PAHs-DDTs Co-contaminated agricultural greenhouse study.

Due to the ecological toxicity and environmental residues, how to remove the persistent organic pollutants (POPs), especially of polycyclic-aromatic-hydrocarbons (PAHs) and dichloro-diphenyl-trichloroethanes (DDTs), from agricultural soil has captured the attention of scholars for a long time. To develop an effective and low-cost in situ co-remediation technique, five independent but complementary treatments were used on an over-standard PAHs-DDTs co-contaminated soil in an agricultural greenhouse. Experimental results identified that the combination of microbe (Bacillus methylotrophicus) - plant (Brassica rapa) could remove rhamnolipid activated PAHs and DDTs effectively after enhanced by Staphylococcus pasteuri. Also, the Benzoapyrene and total DDTs residue in Brassica rapa was up to the standard of National (China) food safety. The lignin enhanced the removal of high-rings PAHs and p-p' DDE but reduced soil microbial biomass carbon and soil enzymes activity (polyphenol oxidase, invertase and acid phosphatase). Pearson correlation analysis showed that polyphenol oxidase activity was significantly related to the PAHs/DDTs dissipation rate. Our research suggested a new amendment that could remediate PAHs/DDTs co-contaminated agricultural soil without interrupting crop production, and the polyphenol oxidase activity should be considered as a micro-ecological indicator in this process.