Co-hydrothermal carbonization of polyvinyl chloride and lignocellulose biomasses for chlorine and inorganics removal

Chromium immobilization from wastewater via iron-modified hydrochar: Different iron fabricants and practicality assessment

The recycling of industrial solid by-products such as red mud (RM) has become an urgent priority, due to their large quantities and lack of reutilization methods can lead to resource wastage. In this work, RM was employed to fabricate green hydrochar (HC) to prepare zero-valent iron (ZVI) modified carbonous materials, and conventional iron salts (IS, FeCl3) was applied as comparison, fabricated HC labeled as RM/HC and IS/HC, respectively. The physicochemical properties of these HC were comprehensively characterized. Further, hexavalent chromium (Cr(VI)) removal performance was assessed (375.66 and 337.19 mg/g for RM/HC and IS/HC, respectively). The influence of dosage and initial pH were evaluated, while isotherms, kinetics, and thermodynamics analysis were also conducted, to mimic the surface interactions. The stability and recyclability of adsorbents also verified, while the practical feasibility was assessed by bok choy-planting experiment. This work revealed that RM can be used as a high value and green fabricant for HC the effective removal of chromium contaminants from the wastewater.

In situ reductive dehalogenation of groundwater driven by innovative organic carbon source materials: Insights into the organohalide-respiratory electron transport chain

In situ bioremediation using organohalide-respiring bacteria (OHRB) is a prospective method for the removal of persistent halogenated organic pollutants from groundwater, as OHRB can utilize H₂ or organic compounds produced by carbon source materials as electron donors for cell growth through organohalide respiration. However, few previous studies have determined the suitability of different carbon source materials to the metabolic mechanism of reductive dehalogenation from the perspective of electron transfer. The focus of this critical review was to reveal the interactions and relationships between carbon source materials and functional microbes, in terms of the electron transfer mechanism. Furthermore, this review illustrates some innovative strategies that have used the physiological characteristics of OHRB to guide the optimization of carbon source materials, improving the abundance of indigenous dehalogenated bacteria and enhancing electron transfer efficiency. Finally, it is proposed that future research should combine multi-omics analysis with machine learning (ML) to guide the design of effective carbon source materials and optimize current dehalogenation bioremediation strategies to reduce the cost and footprint of practical groundwater bioremediation applications.

Co-hydrothermal carbonization of polyvinyl chloride and lignocellulose biomasses: Influence of biomass feedstock on fuel properties and combustion behaviors

Co-hydrothermal carbonization (co-HTC) of lignocellulose biomass (LB) and chlorinated waste could produce value-added co-hydrochar while simultaneously removing inorganic metal salts and organic chlorine to the liquid phase. However, there is a lack of understanding of the influence of LB feedstocks on the fuel properties and combustion behaviors of co-hydrochars. Therefore, co-hydrochars derived from co-HTC of pine, bamboo, corncob, wheat stalk, and corn stalk with polyvinyl chloride (PVC) at the mass ratio of 9:1 under 260 °C for 30 min were tested. PVC facilitated the hydrolysis, dehydration, and polymerization of LB compositions (hemicellulose, cellulose, soluble lignin, and insoluble lignin). In turn, these LB compositions could prevent PVC aggregation and promote PVC substitution. Hydrochar fragments could coat the PVC surface and hinder its hydrolysis. Interactions between LB compositions and PVC improved the fuel properties and combustion behaviors of co-hydrochars derived from bamboo, corncob, wheat stalk, and corn stalk while decreasing the fuel properties and combustion behaviors of co-hydrochar derived from pine (HC-PPE). Except for HC-PPE, the fuel ratio (fixed carbon/volatile matter) of co-hydrochars increased to 0.90-1.18 and their HHVs reached approximately 17.5-32.45 MJ/kg without an increased risk of chlorine corrosion. The combustion of co-hydrochars was easier and more stable due to their higher ignition and burnout temperatures and lower activation energies. These findings provide comprehensive knowledge of the LB feedstocks influence on fuel properties and combustion behaviors of co-hydrochars, which would contribute to the cost-effective use of LB and chlorinated wastes.