One-Pot Synthesis of Biochar from Industrial Alkali Lignin with Superior Pb(II) Immobilization Capability.

This study synthesized biochar through a one-pot pyrolysis process using IALG as the raw material. The physicochemical properties of the resulting biochar (IALG-BC) were characterized and compared with those of biochar derived from acid-treated lignin with the ash component removed (A-IALG-BC). This study further investigated the adsorption performances and mechanisms of these two lignin-based biochars for Pb(II). The results revealed that the high ash content in IALG, primarily composed of Na, acts as an effective catalyst during pyrolysis, reducing the activation energy and promoting the development of the pore structure in the resulting biochar (IALG-BC). Moreover, after pyrolysis, Na-related minerals transformed into particulate matter sized between 80 and 150 nm, which served as active adsorption sites for the efficient immobilization of Pb(II). Adsorption results demonstrated that IALG-BC exhibited a significantly superior adsorption performance for Pb(II) compared to that of A-IALG-BC. The theoretical maximum adsorption capacity of IALG-BC for Pb(II), derived from the Langmuir model, was determined to be 809.09 mg/g, approximately 40 times that of A-IALG-BC. Additionally, the adsorption equilibrium for Pb(II) with IALG-BC was reached within approximately 0.5 h, whereas A-IALG-BC required more than 2 h. These findings demonstrate that the presence of inorganic mineral components in IALG plays a crucial role in its resource utilization.

Highly efficient Ni(II) adsorption by industrial lignin-based biochar: a pivotal role of dissolved substances within biochar.

In the context of carbon neutrality, promoting resource utilization of industrial alkali lignin addressing heavy metal pollution is crucial for China's pollution alleviation and carbon reduction. Microwave pyrolysis produced functionalized biochar from industrial alkali lignin for Ni(II) adsorption. LB400 achieved 343.15 mg g-1 saturated adsorption capacity in 30 min. Pseudo-second-order kinetic and Temkin isotherm models accurately described the adsorption, which was endothermic and spontaneous (ΔGÏ´ < 0, ΔHÏ´ > 0). Quantitative analysis revealed that both dissolved substances and carbon skeleton from biochar contributed to adsorption, with the former predominates (93.76%), including mineral precipitation NiCO3 (Qp) and adsorption of dissolved organic matter (QDOM). Surface complexation (Qc) and ion exchange (Qi) on the carbon skeleton accounted for 6.3%. Higher biochar preparation temperature reduced Ni(II) adsorption by dissolved substances. Overall, biochar which comes from the advantageous disposal of industrial lignin effectively removes Ni(II) contamination, encouraging ecologically sound treatment of heavy metal pollution and sustainable resource utilization.

Enhancement of Cr(VI) adsorption on lignin-based carbon materials by a two-step hydrothermal strategy: Performance and mechanism.

Cr(VI) is a carcinogenic heavy metal that forms an oxygen-containing anion, which is difficult to remove from water by adsorbents. Here, industrial alkali lignin was transformed into a Cr(VI) adsorbent (N-LC) by using a two-step hydrothermal strategy. The characterization results of the adsorbent showed that O and N were uniformly distributed on the surface of the adsorbent, resulting in a favorable morphology and structure. The Cr(VI) adsorption of N-LC was 13.50 times that of alkali lignin, and the maximum was 326.10 mg g-1, which confirmed the superiority of the two-step hydrothermal strategy. After 7 cycles, the adsorption of N-LC stabilized at approximately 62.18 %. In addition, in the presence of coexisting ions, N-LC showed a selective adsorption efficiency of 85.47 % for Cr(VI), which is sufficient to support its application to actual wastewaters. Model calculations and characterization showed that N and O groups were the main active factors in N-LC, and CO, -OH and pyridinic-N were the main active sites. This study provides a simple and efficient method for the treatment of heavy metals and the utilization of waste lignin, which is expected to be widely applied in the environmental, energy and chemical industries.

High capacity adsorption of oxytetracycline by lignin-based carbon with mesoporous structure: Adsorption behavior and mechanism.

In this study, an adsorbent with mesoporous structure and PO/PO bonds is prepared by hydrothermal and phosphoric acid activation from industrial alkali lignin for the adsorption of oxytetracycline (OTC). The adsorption capacity is 598 mg/g, which is three times higher than that of the adsorbent with microporous structure. The rich mesoporous structure of the adsorbent provides adsorption channels and filling sites, and π-π attraction, cation-π interaction, hydrogen bonds, and electrostatic attraction provide adsorption forces at the adsorption sites. The removal rate of OTC exceeds 98 % over a wide range of pH values (3-10). It has high selectivity for competing cations in water, with higher than 86.7 % removal rate of OTC from medical wastewater. After 7 consecutive adsorption-desorption cycles, the removal rate of OTC remains as high as 91 %. This efficient removal rate and excellent reusability indicate the strong potential of the adsorbent for industrial applications. This study prepares a highly efficient, environmentally friendly antibiotic adsorbent that can not only efficiently remove antibiotics from water but also recycle industrial alkali lignin waste.

Synthesis of honeycomb lignin-based biochar and its high-efficiency adsorption of norfloxacin.

In this study, honeycomb lignin-based biochar (HLB) was prepared by hydrothermal activation using industrial lignin as raw material to remove norfloxacin from water. Batch adsorption test results showed that HLB has a strong ability to remove norfloxacin at a wide pH. The maximum adsorption capacity was 529.85 mg/g at 298 K, which is 1.52-fold to 201.46-fold higher than that of other reported materials. HLB showed good selectivity and recycling ability for the adsorption of norfloxacin, the removal rate of NOR reached 99.5% in the presence of competitive ions and maintained at least 98% removal rate after 12 adsorption cycles. The removal rate of norfloxacin in different water reached more than 99% within 8 mins. Pore filling, electrostatic interaction, π-π interaction, and hydrogen bond contributed significantly to the removal of norfloxacin. Among them, the highly aromatized structure of HLB and the abundant oxygen-containing functional groups (OH, CO, etc.) promoted π-π interaction.

Study on the Effect of 1-Butanol Soluble Lignin on Temperature-Sensitive Gel.

A protocol for the fractionation of lignin with 1-butanol as solvent has been proposed in order to improve the utilization of industry alkali lignin. 1-butanol soluble lignin (BSL) was used as a building block for temperature-sensitive hydrogel with N-isopropylacrylamide (NIPAAm) through graft polymerization. The result shows that 1-butanol fractionation is an effective method to improve the molecular weight homogeneity of lignin (PDI, 2.5 to 1.83) and increase the hydroxyl group content (0.585⁻1.793 mmol/g). The incorporation of BSL into the temperature-sensitive hydrogel can enhance the thermal stability and increase the hydrophobicity of the gel, which leads to a decrease in lower critical solution temperature (LCST). In addition, the compression strength, swelling ratio, and pore size of the gel can be adjusted by the dosage of lignin. This stimuli-responsive gel, with an LCST around 32 °C, is expected to be applied in the agricultural field as a pesticide carrier by stimulating release and absorption properties based on the change in natural environmental temperature.