In this paper, the biochar prepared by pyrolysis biomass of Water Hyacinth were used as adsorption materials. The effects of initial concentration, adsorption temperature and electrolyte concentration on the adsorption process were analyzed. The adsorption effect of biochar prepared from the stem and root parts of biomass on Cd2+ in solution was investigated, and the interaction between leaching rule of alkali (earth) metal K+, Mg2+, Ca2+ and adsorption of heavy metal ions in the process of adsorption was studied. The results showed that the biochar prepared by pyrolysis of stem biomass (SBC) has a richer pore structure. Compared with the biochar prepared by root biomass (RBC), the specific surface area and pore volume of SBC increased by 25.85% and 27.91% respectively. This phenomenon indicated that SBC had a stronger adsorption effect than RBC. At 25ºC, the maximum adsorption capacity of RBC and SBC for Cd2+ was 77.20 mg g-1 and 87.20 mg g-1, respectively. Isothermal adsorption experiments and ionic strength experiments showed that the increase of temperature could promote the adsorption of Cd2+ by biochar. The adsorption process has a high degree of fitting with the Langmiur model, as well as the pseudo-second-order model. The adsorption sites were normally on the inner and outer surfaces of biochar, and the adsorption process was multi-molecular layer adsorption. In addition, the adsorption of Cd2+ by biochar had a correlation with the leaching of alkali (earth) metal in the system. In the adsorption process, the leaching of alkali (earth) metals was affected by the initial concentration of Cd2+ in the solution, and SBC leached more alkali (earth) metals than RBC, which proved that SBC has more active sites and can replace heavy metals in the solution. This study proved that Water Hyacinth biochar owned characteristics of high recovery and low economic cost, which showed good adsorption to Cd2+ polluted wastewater and was feasible as a heavy metal adsorption material.

The process of ball milling and the materials that compose planetary ball mills are highly complex, and the existing research on the change in ball-milling energy is not mature. The theoretical model of a ball mill was established for the first time to simulate the motion, collision process, energy transfer, and temperature change of small balls during the ball-milling process. Furthermore, by comparing the information with the experimental data for a ball mill, the motion trajectory of the grinding ball, and the energy transfer between the balls and materials were studied, and the micro process during milling was discussed. This study provides a certain theoretical basis for the follow-up engineering application.

To evaluate the efficacy of biochelators for phytoremediation of cadmium (Cd), effects of biochelators (humic acid, HA; polyaspartic acid, PASP; rhamnolipid, RLs) and synthetic chelator (sodium tripolyphosphate, STPP) on the growth, accumulation, and antioxidant index of Cd were investigated in Iris sibirica L. The results indicated that the addition of HA increased the dry weight of leaves and stems, and the addition of PASP, RLs, and STPP increased the growth of leaves but inhibited the growth of stems. The determination of Cd accumulation indicated that HA decreased the content of Cd in all tissues, while the addition of PASP, RLs, and STPP increased the accumulation of Cd in stems and roots. In addition, the determination of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities indicated that the treatment of PASP and RLs increased the activities of antioxidant enzymes, which might be beneficial to the resistance of Cd for Iris sibirica L. Overall, these results indicated that biochelators may improve the phytoremediation efficacy of Iris sibirica L. on Cd polluted paddy field. Among the tested chelators, PASP exhibited the best comprehensive efficacy and the highest commercial potential.

Due to their substantial biomass and rapid growth, emergent plants found in wetlands are viewed as excellent sources for biochar production, which has been demonstrated to serve as an effective substitute for absorbite in the effluent treatment. This article systematically contrasted the physicochemical properties of biochar derived from each section of Iris sibirica L. (designated as BC_R, BC_S, and BC_L) under identical pyrolysis conditions, in order to assess their effectiveness in removing cadmium (Cd) from effluent. Experimental results indicated that the removal efficiencies of Cd among the various biochars followed the order BC_S (19.92 mg/g) > BC_L (19.89 mg/g) > BC_R (13.22 mg/g). The removal of Cd²⁺ by biochar is primarily governed by chemisorption, as described by the Langmuir and Freundlich models. Moreover, different adsorption kinetic models, e.g., first-order kinetics, second-order kinetics, intra-particle diffusion, and the Elovich model, were performed to elucidate the adsorption process. Compared to BC_L and BC_R, the proportions of ion exchange and precipitation were more superior in BC_S, reaching 54% and 31%, respectively, which could serve as an effective adsorbent for metal ions, achieving the maximum adsorption capacity. In addition, precipitation (46%) was predominant during the Cd²⁺ adsorption process through BC_R. Therefore, BC_R was more suitable for the acidic wastewater treatment. This study provided an in-depth understanding of the cadmium removal behavior through biochar obtained from different part (roots, stems, and leaves) of wetland plants and introduced a new option for efficient utilization of waste biomass.

Biochars produced from aquatic plants have attracted increasing attention for the removal of heavy metals from the environment. Therefore, biochars derived from the roots (CBR), stems (CBS) and leaves (CBL) of cattail were investigated in this paper for their higher adsorption capacity, particularly for Cd(II). The adsorption characteristics and the leaching of alkali (soil) metals within biochars obtained from the different tissues of cattail were also discussed. The results showed that the specific surface area of cattail root biochar reached 15.758 m² g⁻¹. Langmuir, Freundlich and D-R isotherm equations were used to fit the experimental data, and the last equation revealed the best fitting result. The adsorption kinetics for Cd(II) removal were determined by using two different models. The experimental data for CBR and CBS were in good agreement with the pseudo second-order model, whereas the pseudo first-order model provided a better fit for CBL. The amount of leached K reached 73.214 mg g⁻¹ in CBS (55.087 mg g⁻¹ in CBL), which was almost an order of magnitude higher than those of Mg and Ca. The experimental data showed that the leached Mg and Ca metals in CBL had maximum levels of 6.543 and 10.339 mg g⁻¹, respectively. The mechanism of Cd(II) sorption by the biochar is complex and probably involves a combination of mass transfer, ion exchange, and mineral precipitation through the macropores and micropores of the biochar in the sorption process.

In the electrocatalytic (EC) degradation process, challenges such as inefficient mass transfer, suboptimal mineralization rates, and limited current efficiency have restricted its broader application. To overcome these obstacles, this study synthesized spherical particle electrodes (FeNi@BC) with superior electrocatalytic performance using a bio-inspired preparation method. A three-dimensional electrocatalytic oxidation system based on FeNi@BC electrode, EC/FeNi@BC, showed excellent degradation efficiency of sulfamethoxazole (SMX), reaching 0.0456 min⁻¹. Quenching experiments and electron paramagnetic resonance experiments showed that the excellent SMX degradation efficiency in the EC/FeNi@BC system was attributed to the synergistic effect of multiple reactive oxygen species (ROS) and revealed their evolution path. Characterization results showed that FeNi₃ generated in the FeNi@BC electrode was a key bimetallic active site for improving electrocatalytic activity and repolarization ability. More importantly, the degradation pathway and reaction mechanism of SMX in the EC/FeNi@BC system were proposed. In addition, the influencing factors of the reaction system (voltage, pH, initial SMX concentration, electrode dosage, and sodium sulfate concentration, etc.) and the stability of the catalyst (maintained more than 81% after 5 cycles) were systematically evaluated. This study may provide help for the construction of environmentally friendly catalytic and efficient degradation of organic pollutants.