Preparation of binder-less activated char briquettes from pyrolysis of sewage sludge for liquid-phase adsorption of methylene blue

Synergistic mechanisms for the superior sorptive removal of aquatic pollutants via functionalized biochar-clay composite

This study investigated the successful synthesis of functionalized algal biochar-clay composite (FBKC). Subsequently, the sorption performance of FBKC towards norfloxacin (NFX) antibiotic and crystal violet dye (CVD) from water was extensively assessed in both batch and continuous flow systems. A series of characterization techniques were carried out for FBKC and the utilized precursors, indicating that the surface area of FBKC was increased thirty-fold with a well-developed pore structure compared to the original precursors. FBKC demonstrated a maximum sorption capacity of 192.80 and 281.24 mg/g for NFX and CVD, respectively. The suited fitting of the experimental data to Freundlich and Clark models suggested multi-layer sorption of NFX/CVD molecules. The mechanistic studies of NFX/CVD sorption onto FBKC unveiled multiple mechanisms, including π-π interaction, hydrogen bonding, electrostatic attraction, and surface/pore filling effect. The estimated cost of 5.72 €/kg and superior sorption capacity makes FBKC an efficient low-cost sorbent for emergent water pollutants.

Facile Synthesis and Life Cycle Assessment of Highly Active Magnetic Sorbent Composite Derived from Mixed Plastic and Biomass Waste for Water Remediation

Plastic and biomass waste pose a serious environmental risk; thus, herein, we mixed biomass waste with plastic bottle waste (PET) to produce char composite materials for producing a magnetic char composite for better separation when used in water treatment applications. This study also calculated the life cycle environmental impacts of the preparation of adsorbent material for 11 different indicator categories. For 1 functional unit (1 kg of pomace leaves as feedstock), abiotic depletion of fossil fuels and global warming potential were quantified as 7.17 MJ and 0.63 kg CO₂ equiv for production of magnetic char composite materials. The magnetic char composite material (MPBC) was then used to remove crystal violet dye from its aqueous solution under various operational parameters. The kinetics and isotherm statistical theories showed that the sorption of CV dye onto MPBC was governed by pseudo-second-order, and Langmuir models, respectively. The quantitative assessment of sorption capacity clarifies that the produced MPBC exhibited an admirable ability of 256.41 mg g^-1. Meanwhile, the recyclability of 92.4% of MPBC was demonstrated after 5 adsorption/desorption cycles. Findings from this study will inspire more sustainable and cost-effective production of magnetic sorbents, including those derived from combined plastic and biomass waste streams.

Adsorption of Organic Compounds on Adsorbents Obtained with the Use of Microwave Heating

Activated carbons were obtained by physical and chemical activation of the residue of supercritical extraction of green tea leaves. All the adsorbents obtained were characterized by: elemental analysis, low-temperature nitrogen adsorption, and the contents of acidic and basic oxygen functional groups on the surface of activated carbons by the Boehm method. The activated carbons were micro- or micro-mesoporous with well-developed surface area ranging from 520 to 1085 m²/g and total pore volume from 0.62 to 0.64 cm³/g. The physical activation of the precursor led to the strongly basic character of the surface. Chemical activation with 50% solution of H₃PO₄ of the residue of supercritical extraction of green tea leaves promoted the generation of acidic functional groups. All adsorbents were used for methylene blue and methyl red adsorption from the liquid phase. The influence of the activation method, pH of the dye solution, contact time of adsorbent with adsorbate, the temperature of adsorption, and rate of sample agitation on the effectiveness of organic dyes removal was evaluated and optimized. In the process of methylene blue adsorption on adsorbents, an increase in the sorption capacity was observed with increasing pH of the adsorbate, while in the process of methyl red adsorption, the relation was quite the reverse. The adsorption data were analyzed assuming the Langmuir or Freundlich isotherm models. The Langmuir model better described the experimental results, and the maximum sorption capacity calculated for this model varied from 144.93 to 250.00 mg/g. The results of the kinetic analysis showed that the adsorption of organic dyes on activated carbon was following the pseudo-second-order model. The negative values of the Gibbs free energy indicate the spontaneous character of the process.