Abstract
In this study, the sludge-based biochar was prepared and utilized as an adsorbent for the removal of two commonly used pesticides in agriculture, namely tebuconazole (Teb) and linuron (Lin) in an aqueous solution. The main contributing factors such as biochar preparation conditions, persistent free radicals as well as contact time, agitation speed, biochar dose, temperature, and pH were investigated. The physicochemical properties were characterized by SEM + EDS, FTIR, BET, EPR, etc. The results showed that the maximum adsorption capacities based on the Langmuir model was 7.8650 mg g−1 for tebuconazole and that based on Freundlich model was 9.0645 mg·g-1 for linuron at 25°C. The pseudo-second-order kinetic equations were all fitted well to the kinetic process of the adsorption of the two pesticides with all R2 ≥ 0.915. The maximum values of tebuconazole adsorption capacity occur at pH = 3. Meanwhile, linuron was not affected by pH. Both Cr6+ (r = −0.793∗∗/ −0.943∗∗) and humic acid (r = −0.798∗∗/ −0.947∗∗) significantly inhibited the adsorption amount of tebuconazole and linuron onto the biochar. Electron spin resonance signals (ESR) indicated that environmentally persistent radicals (EPFRs) are preferentially formed at lower pyrolysis temperatures and lower transition metal concentrations. The g-factors for BC400, BC600, BCF400, and BCF600 were 2.0036, 2.0035, 2.0034, and 2.0033, respectively, indicating that the EPFRs mainly have a carbon-centered structure with adjacent oxygen atoms. In addition, to close to the actual situation, natural water (from YanTai) was collected to simulate pesticide contamination. This study demonstrates that sludge-based biochar can achieve efficient removal of tebuconazole and linuron in aqueous environment in a short period of time with no secondary environmental risk especially on the waste activated sludge.
Highlights
Agricultural runoffs and toxic industrial wastewater are two main ways for pesticides to enter natural water [27,28,29,30,31,32,33,34,35]. ere is accumulating evidence that pesticides are widely detected at μg·L−1 levels in the rivers, soils, as well as other environmental compartments, while some compounds are considered reprotoxic [36,37,38]. erefore, researchers are working to develop effective remediation methods or new materials to remove the pesticide residues from aqueous environments [39,40,41,42,43,44]
Compared with BC400, BC600, and BCF400, BCF600 showed a significant improvement on tebuconazole removal
The removal efficiencies of BC400, BC600, and BCF400 biochar were only 31.19%, 29.90%, and 35.75% in 120 min, respectively. e final results showed that the adsorption amount of tebuconazole by BCF600 was approximately 1.82, 2.49, and 2.93 times higher than the maximum adsorption amount of BC400, BC600, and BCF400 in 360 min. e same trend was observed for the linuron adsorption
Summary
The sludge-based biochar was prepared and utilized as an adsorbent for the removal of two commonly used pesticides in agriculture, namely tebuconazole (Teb) and linuron (Lin) in an aqueous solution. e main contributing factors such as biochar preparation conditions, persistent free radicals as well as contact time, agitation speed, biochar dose, temperature, and pH were investigated. e physicochemical properties were characterized by SEM + EDS, FTIR, BET, EPR, etc. e results showed that the maximum adsorption capacities based on the Langmuir model was 7.8650 mg g−1 for tebuconazole and that based on Freundlich model was 9.0645 mg·g-1 for linuron at 25°C. e pseudo-second-order kinetic equations were all fitted well to the kinetic process of the adsorption of the two pesticides with all R2 ≥ 0.915. e maximum values of tebuconazole adsorption capacity occur at pH 3. The sludge-based biochar was prepared and utilized as an adsorbent for the removal of two commonly used pesticides in agriculture, namely tebuconazole (Teb) and linuron (Lin) in an aqueous solution. Is study demonstrates that sludge-based biochar can achieve efficient removal of tebuconazole and linuron in aqueous environment in a short period of time with no secondary environmental risk especially on the waste activated sludge. Linuron (3(3, 4-dichlorophenyl)-1-methoxy-1-methylurea) is applied to the restrained annual gramineous weeds for the sake of economical crop growth (celery, legume, carrot, potato, onion fields, etc.) Because of their physical and Journal of Chemistry chemical properties, high toxicity, and occasionally high endurance in the environment, these pesticides may cause environmental and health problems [20,21,22,23,24,25,26]. Us, the preparation of low-cost adsorbents from different waste materials (domestic, agricultural waste, or industrial byproducts) [59,60,61] is more economical and environmentally advantageous
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