Study on persulfate activated by Ce-modified tea waste biochar to degrade tetracycline

Zinc and sulfur functionalized biochar as a peroxydisulfate activator via deferred ultraviolet irradiation for tetracycline removal

To enhance the degradation of tetracycline class (TC) residuals of high-concentration from pharmaceutical wastewater, a novel zinc (Zn) and sulfur (S) functionalized biochar (SC-Zn), as a peroxydisulfate (PDS) activator, was prepared by two-step pyrolysis using ZnSO4 accumulated water-hyacinth. Results showed that the removal rate of 50, 150, and 250 mg per L TC reached 100%, 99.22% and 94.83% respectively, by the SC-Zn/PDS system at a dosage of 0.3 g per L SC-Zn and 1.2 mM PDS, via the deferred ultraviolet (UV) irradiation design. Such excellent performance for TC removal was due to the synergetic activation of PDS by the biochar activator and UV-irradiation with biochar as a responsive photocatalyst. The functionalization of the co-doped Zn and S endowed the biochar SC-Zn with a significantly enhanced catalytic performance, since Zn was inferred to be the dominant catalytic site for SO4˙- generation, while S played a key role in the synergism with Zn by acting as the primary adsorption site for the reaction substrates. The employed SC-Zn/PDS/UV system had excellent anti-interference under different environmental backgrounds, and compared with the removal rate of TC by adsorption of SC-Zn, the increasing rate in the SC-Zn/PDS/UV system (18.75%) was higher than the sum of the increases in the SC-Zn/PDS (9.87%) and SC-Zn/UV systems (3.34%), furtherly verifying the systematic superiority of this synergy effect. This study aimed to prepare a high-performance functionalized biochar activator and elucidate the rational design of deferred UV-irradiation of PDS activation to efficiently remove high-concentration antibiotic pollutants.

Removal performance and mechanisms of aqueous Cr (VI) by biochar derived from waste hazelnut shell

Cr (VI) is still of great concern due to its high toxicity, solubility, and mobility. The transformation of waste biomass to biochar is favorable for sustainable development. Hazelnut shell, an agriculture waste, was utilized as precursor to prepare biochar at 700 °C and firstly conducted for Cr (VI) removal. Nearly all 50 mg L-1 of Cr (VI) was removed from aqueous media in 180 min under the optimal conditions. The best compliance with pseudo-second-order kinetic model (R2 = 0.999) and Langmuir isotherm model (R2 = 0.999) indicated Cr (VI) removal was a monolayer chemisorption process. The hazelnut shell biochar exhibited superior performance on Cr (VI) removal at low pH (2.0) and Cr (VI) concentrations (≤ 50 mg L-1). Various techniques illustrated that the predominant mechanism of Cr (VI) removal by hazelnut shell biochar involved electrostatic attraction, reduction, and complexation. This study provides a promising low-cost alternative for Cr (VI) elimination from acidic wastewater and groundwater after extraction following by pH adjustment to 2.0.