title: Characterization of potassium hydroxide (KOH) modified hydrochars from different feedstocks for enhanced removal of heavy metals from water.
abstract: Hydrochars produced from different feedstocks (sawdust, wheat straw, and corn stalk) via hydrothermal carbonization (HTC) and KOH modification were used as alternative adsorbents for aqueous heavy metals remediation. The chemical and physical properties of the hydrochars and KOH-treated hydrochars were characterized, and the ability of hydrochars for removal of heavy metals from aqueous solutions as a function of reaction time, pH, and initial contaminant concentration was tested. The results showed that KOH modification of hydrochars might have increased the aromatic and oxygen-containing functional groups, such as carboxyl groups, resulting in about 2-3 times increase of cadmium sorption capacity (30.40-40.78 mg/g) compared to that of unmodified hydrochars (13.92-14.52 mg/g). The sorption ability among different feedstocks after modification was as the following: sawdust > wheat straw > corn stack. Cadmium sorption kinetics on modified hydrochars could be interpreted with a pseudo-second order, and sorption isotherm was simulated with Langmuir adsorption model. High cadmium uptake on modified hydrochars was observed over the pH range of 4.0-8.0, while for other heavy metals (Pb(2+), Cu(2+), and Zn(2+)) the range was 4.0-6.0. In a multi-metal system, the sorption capacity of heavy metals by modified hydrochars was also higher than that by unmodified ones and followed the order of Pb(II) > Cu(II) > Cd(II) > Zn(II). The results suggest that KOH-modified hydrochars can be used as a low cost, environmental-friendly, and effective adsorbent for heavy metal removal from aqueous solutions.
authors.affiliation: College of Environmental Science and Engineering, Nankai University, Tianjin, 300071, China.
authors.forename: Kejing
authors.initials: K
authors.lastname: Sun
authors.affiliation: College of Environmental Science and Engineering, Nankai University, Tianjin, 300071, China. tangjch@nankai.edu.cn.|Tianjin Engineering Centre of Environmental Diagnosis and Contamination Remediation, Tianjin, 300071, China. tangjch@nankai.edu.cn.|Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin, 300071, China. tangjch@nankai.edu.cn.
authors.forename: Jingchun
authors.initials: J
authors.lastname: Tang
authors.affiliation: College of Environmental Science and Engineering, Nankai University, Tianjin, 300071, China.|Tianjin Engineering Centre of Environmental Diagnosis and Contamination Remediation, Tianjin, 300071, China.|Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin, 300071, China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Gong
authors.affiliation: College of Environmental Science and Engineering, Nankai University, Tianjin, 300071, China.
authors.forename: Hairong
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000327:Adsorption; D004391:Dust; D006878:Hydroxides / Q000737:chemistry; D007700:Kinetics; D019216:Metals, Heavy / Q000302:isolation & purification*; D035261:Plant Components, Aerial / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D014908:Triticum / Q000737:chemistry; D014867:Water; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification; D003313:Zea mays / Q000737:chemistry
chemical_list: D004391:Dust; D006878:Hydroxides; D019216:Metals, Heavy; D017680:Potassium Compounds; D014874:Water Pollutants, Chemical; D014867:Water; C029943:potassium hydroxide
keywords: Heavy metal; Hydrochar; Hydrothermal carbonization; Modification; Sorption