molecules Review Engineered Zero-Dimensional Fullerene/Carbon Dots-Polymer Based Nanocomposite Membranes for Wastewater Treatment Mona Jani 1,*, Jose A. Arcos-Pareja 1 and Ming Ni 2,* 1 Department of Physical Sciences and Nanotechnology, Yachay Tech University, 100119 Urcuquí, Ecuador; [email protected] 2 GeneScript, Zhenjiang, Jiangsu 212000, China * Correspondence: [email protected] (M.J.); [email protected] (M.N.) Academic Editor: Minas M. Stylianakis Received: 21 February 2020; Accepted: 13 April 2020; Published: 26 October 2020 Abstract: With the rapid growth of industrialization, diverse pollutants produced as by-products are emitted to the air-water ecosystem, and toxic contamination of water is one of the most hazardous environmental issues. Various forms of carbon have been used for adsorption, electrochemical, and ion-exchange membrane filtration to separation processes for water treatment. The utilization of carbon materials has gained tremendous attention as they have exceptional properties such as chemical, mechanical, thermal, antibacterial activities, along with reinforcement capability and high thermal stability, that helps to maintain the ecological balance. Recently, engineered nano-carbon incorporated with polymer as a composite membrane has been spotlighted as a new and effective mode for water treatment. In particular, the properties of zero-dimensional (0D) carbon forms (fullerenes and carbon dots) have encouraged researchers to explore them in the field of wastewater treatment through membrane technologies as they are biocompatible, which is the ultimate requirement to ensure the safety of drinking water. Thus, the purpose of this review is to highlight and summarize current advances in the field of water purification/treatment using 0D carbon-polymer-based nanocomposite membranes. Particular emphasis is placed on the development of 0D carbon forms embedded into a variety of polymer membranes and their influence on the improved performance of the resulting membranes. Current challenges and opportunities for future research are discussed. Keywords: fullerenes; carbon dots; biocompatibility; 0D carbon-polymer nanocomposite membranes; water treatment 1. Introduction Hygienic water is vital for the ecological environment and human health. Vast amounts of water deteriorated by contaminants are discharged from industry or through intensification of human activity, thus it is significant to implement conventional water treatments, resource recovery and purification technologies [1]. Increasing demands for advanced water treatments have stimulated an intensive exploration for use of high-performance membrane-based technologies. Membrane-based technologies are exceptionally attractive as they are highly efficient, have low energy consumption, easy scale-up feasibility and have a small carbon footprint [2,3]. Diverse membrane-based technologies have been used for the treatment of water, including micro/ultra/nano-filtration (µF/UF/NF), reverse osmosis and membrane distillation [4]. A common driving force for membrane separation is pressure [5]. Amongst membrane-based technologies, the most common one is commercialized reverse osmosis, which is based on pressure driving forces, consumes high energy and has high operational costs, thus hindering its wider application [6]. For the development of these membrane-based technologies for water purification, Molecules 2020, 25, 4934; doi:10.3390/molecules25214934 www.mdpi.com/journal/molecules Molecules 2020, 25, x FOR PEER REVIEW 2 of 28 Molecules 2020, 25, 4934 2 of 28 and has high operational costs, thus hindering its wider application [6]. For the development of these membrane-based technologies for water purification, membranes made of polymeric materials are membranesattracting increased made ofresearch polymeric interest materials. Polymeric are membranes attracting increased are energy research efficient, interest. can be easily Polymeric scaled, membranesoffer time-saving are energy processes, efficient, they canare behighly easily permeable scaled, o fftoer water time-saving, have stable processes, structure theys, are highlyhighly permeablewater selectiv to water,e, have have excellent stable solute structures, rejection are highlyat low wateroperation selective, pressur havees and excellent are sturdily solute rejectionresistant atto lowoxidation operation and pressuresfouling. 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Some preparation/ amide, and methods chitosan for forming are preferred. polymeric Some membranes preparation are methodselectrospinning for forming [7], track polymeric-etching, membranes stretching, arevapor electrospinning deposition, sol [7-],gel track-etching, process, phase stretching, inversion, vapor and deposition,interfacial polymerization sol-gel process, phase(IP) [8]. inversion, Thin film and composite interfacial (TFC) polymerization membranes (IP) are [8]. fabricated Thin film composite using IP, (TFC)which membranesis essential are for fabricated commercialization using IP, which of reverse is essential osmosis for commercialization and NF processes of. reverseMost of osmosis these andmembranes NF processes. produced Most via of IP these have membranes polyamide produced as a skinny via layer IP have on polyamidethe upper part as a skinnyof a membrane layer on thesupport. upper The part active of a membranemonomers support.used to form The functional active monomers polyamide used skinny to form layers functional are commonly polyamide m- skinnyphenylenediamine layers are commonly and trimesoylm-phenylenediamine chloride. The synthetic and trimesoyl pathway chloride. for preparation The synthetic of membranes pathway for is preparationshown in Scheme of membranes 1. The p isolyamide shown in membrane Scheme1. Thes derived polyamide from membranes monomers derivedhave good from desalination monomers haveproperties good [9]. desalination properties [9]. Scheme 1. Commercial polyamide membrane derived from monomers such as m-phenylenediamine andScheme trimesoyl 1. Commercial chloride via polyamide IP. Reproduced membrane with permissionderived from from monomers [9]. Crown such copyright as m-phenylenediamine© 2020 published byand Elsevier trimesoyl B.V. chloride via IP. Reproduced with permission from [9]. Crown copyright© 2020 published by Elsevier B.V. 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