Simple fabrication of carbon quantum dots and activated carbon from waste wolfberry stems for detection and adsorption of copper ion.

Removal of heavy metal pollution is an endless topic, because heavy metals can cause irreversible damage to the human body and environment. It is urgent to develop novel materials for detection and adsorption of heavy metal ions. In this paper, waste wolfberry straw was utilized as a carbon source, and two simple methods were developed to successfully prepare activated carbon (AC) and carbon quantum dots (CQDs). The fabrication conditions were optimized by adjusting the mass ratio of precursor to activator, type of activator and activation times. When sodium hydroxide (NaOH) was selected as an activator (6 : 1, mass ratio of NaOH to AC-precursor), and the activation was performed at 600 °C for 1 h, the highest specific surface area of the obtained AC-NaOH-3 reached 3016 m2 g-1. The adsorption capacity for copper ions (Cu2+) reached 68.06 mg g-1. The preparation conditions for CQDs were also optimized by adjusting the concentration of wolfberry stem, reaction time and temperature. When the wolfberry stem concentration was 7.5 g L-1, and the activation was performed at 200 °C for 24 h, the obtained CQDs exhibited strong fluorescence emission in the blank and 12 kinds of metal ion solutions, respectively, however, the fluorescence intensity was remarkably decreased after adding Cu2+. In the range of 10-80 nM, the linear correlation coefficient between the concentration of Cu2+ and fluorescence intensity of CQDs was 0.992, and the limit of detection was 2.83 nmol L-1. Thus, these two kinds of materials were prepared from wolfberry stem, which opened up a new way for the application in adsorption and detection of copper ions.

Ganoderma lucidum bran-derived blue-emissive and green-emissive carbon dots for detection of copper ions.

Ganoderma lucidum bran (GB) has a broad application prospect in the preparation of activated carbon, livestock feed, and biogas, but the preparation of carbon dots (CDs) from GB has never been reported. In this work, GB was applied as a carbon source and nitrogen source to prepare both blue fluorescent CDs (BCDs) and green fluorescent CDs (GCDs). The former were prepared at 160 °C for 4 h by a hydrothermal approach, while the latter were acquired at 25 °C for 24 h by chemical oxidation. Two kinds of as-synthesized CDs exhibited unique excitation-dependent fluorescence behavior and high fluorescent chemical stability. Based on the fantastic optical behavior of the CDs, they were utilized as probes for fluorescent determination of copper ions (Cu2+). In the range of 1-10 µmol L-1, the fluorescent intensity of BCDs and GCDs decreased linearly with the increase of Cu2+ concentration; the linear correlation coefficient reached 0.9951 and 0.9982, and the limit of detection (LOD) was 0.74 and 1.08 µmol L-1, respectively. In addition, these CDs remained stable in 0.001-0.1 mmol L-1 salt solutions; BCDs were more stable in the neutral pH range, but GCDs were more stable in neutral to alkaline conditions. The CDs prepared from GB are not only simple and low-cost, but also can realize the comprehensive utilization of biomass.

Adsorption of heavy metal onto biomass-derived activated carbon: review.

Due to the rapid development of the social economy and the massive increase in population, human beings continue to undertake processing, and commercial manufacturing activities of heavy metals, which has caused serious damage to the environment and human health. Heavy metals lead to serious environmental problems such as soil contamination and water pollution. Human health and the living environment are closely affected by the handling of heavy metals. Researchers must find several simple, economical and practical methods to adsorb heavy metals. Adsorption technology has been recognized as an efficient and economic strategy, exhibiting the advantages of recovering and reusing adsorbents. Biomass-derived activated carbon adsorbents offer large adjustable specific surface area, hierarchically porous structure, strong adsorption capacity, and excellent high economic applicability. This paper focuses on reviewing the preparation methods of biomass-derived activated carbon in the past five years. The application of representative biomass-derived activated carbon in the adsorption of heavy metals preferentially was described to optimize the critical parameters of the activation type of samples and process conditions. The key factors of the adsorbent, the physicochemical properties of the heavy metals, and the adsorption conditions affecting the adsorption of heavy metals are highlighted. In addition, the challenges faced by biomass-derived activated carbon are also discussed.

Preparation of Ganoderma Lucidum Bran-Based Biological Activated Carbon for Dual-Functional Adsorption and Detection of Copper Ions.

In this paper, Ganoderma lucidum bran was explored as the precursor to fabricate biomass activated carbon. When potassium hydroxide was selected as an activator (1:6, mass ratio of AC-12 to potassium hydroxide), and the activation condition was 700 °C at 5 h, the highest specific surface area reached 3147 m2 g-1. Carbon dots were prepared with citric acid monohydrate and thiourea as precursors and then loaded onto the surface of activated carbon by a simple and green method. Activated carbon for dual-functional had a high adsorption capacity. Additionally, based on its unique optical properties, the fluorescence response for detecting copper ion was established. The fluorescence intensity of the materials decreased linearly with the increase of copper ion concentration, in the range of 10-50 nmol L-1. The research opened up a new way for applying biomass activated carbon in the field of adsorption and detection. Highlights: (1) Carbon dots were loaded on the surface of activated carbon; (2) the simultaneous adsorption and detection were realized; (3) it provides a way for the preparation of dual-functional materials.

Polyethyleneimine modified activated carbon for high-efficiency adsorption of copper ion from simulated wastewater.

In this study, activated carbon (AC) was chemically activated using sodium hydroxide (NaOH), and polyethyleneimine (PEI) was grafted onto the AC using glutaraldehyde as a cross-linking agent. Then the modified AC was applied to treat water samples containing copper ions (Cu2+). Preparation of AC-NaOH@PEI. The grafted AC was characterized, demonstrating that the specific surface area of material decreased from 959.3 to 556.9 m2/g. The ζ-potential changed from -27.2 to 10.4 mV, and the presence of a distinct flocculation on the surface of the AC was observed via scanning electron microscopy. The results demonstrated that PEI was successfully grafted onto the surface of AC. Furthermore, the adsorption results indicated that the Cu2+ adsorption capacity of AC-NaOH@PEI was greatly enhanced with increasing PEI loading. The adsorption amount of Cu2+ by the grafted AC-NaOH@PEI-200 increased from 20.02 to 47.8 mg/g. In addition, the adsorption of Cu2+ by AC-NaOH@PEI was a pH dependent process. At a pH of 6, the maximum removal rate reached 93%. The adsorption process is better described by the Langmuir and quasi-second order adsorption models, signifying that the adsorption of Cu2+ on AC@PEI consists of monolayer adsorption and chemisorption. After four adsorption-desorption cycles, AC@PEI exhibited high adsorption capacity for Cu2+, indicating that it has good regeneration ability. It is a promising adsorbent material.

Adsorption of cadmium ions from simulated battery wastewater by polyethylene polyamine-modified activated carbon.

The objective of this work was to study the treatment of wastewater containing cadmium ions (Cd2+). Activated carbon (AC) was modified with potassium hydroxide (KOH) and polyethylene polyamine (PEPA). The structure and morphology of the modified AC was characterized. The effect of pH on adsorption was investigated, and the binary competitive adsorption and the reusability of the modified AC were studied. Subsequently the modified AC was used as an adsorbent for the removal of Cd2+ from wastewater. The adsorption capacity of optimized modified AC was 9.7 times that of unmodified AC. Kinetic adsorption curves were in accordance with pseudo-second-order kinetics, and the isothermal curves were in accordance with the Langmuir equation. The results indicate that the AC has potential in the treatment of the wastewater containing Cd2+ discharged from chemical plants during battery manufacturing.