The present work aims to prepare an ecofriendly and effective material for adsorption of heavy metals, especially iron and manganese from polluted water. Chitosan nanoparticles were prepared from the extracted chitosan of shrimp shells waste using a traditional ionic gelation method in presence of sodium tripolyphosphate as a cross-linker. To confirm the polymer structure and its characteristics, the prepared nanoparticles were characterized using FT-IR, X-Ray diffraction, TEM and SEM. Molecular weight, the degree of de-acetylation, ash content, particle size and zeta potential values were 3923 D, 75 %, 4 %, 331 nm and +38 mv, respectively. A batch equilibrium experiments were carried out to evaluate the chitosan nanoparticles as adsorbents of Fe (II) and Mn (II) ions from aqueous solutions. The removal efficiency and adsorption capacity were studied at different contact times, pH of the sorption medium, and initial metal ion concentration in the feed solution. The removal efficiency and maximum adsorption capacity of Fe (II) and Mn (II) were 99.8, 116.2 mg/g and 95.3%, 74.1mg/g, respectively. From the adsorption isotherm and kinetic studies, it was found that the Langmuir and the pseud-second order models, respectively, were more fitted in this study.

A novel adsorbent of chitosan-1,2-Cyclohexylenedinitrilotetraacetic acid – graphene oxide (Cs/CDTA/GO) nanocomposite was successfully prepared in the presence of glutaraldehyde as cross linker. The adsorption and removal efficiency of hexavalent chromium (Cr6+) using Cs/CDTA/GO adsorbent were investigated at different adsorption conditions. The prepared adsorbent was characterized by FTIR and SEM. The effects of adsorbent chemical composition, CDTA/GO concentration, adsorbent dose, pH, temperature, contact time and initial metal ion concentration on Cr6+ sorption were investigated. The results showed that the optimum adsorbent dose was 2g/l at pH of 3.5 and equilibrium time of 60min. In addition, the temperature and pH were shown with great influence of the adsorption process. The adsorption kinetics of Cr6+ onto Cs/CDTA/GO followed the pseudo-second order model and the adsorption isotherm was well fitted by the Langmuir model. The maximum adsorption capacity of the adsorbent was 166.98mg/g, and the equilibrium parameter (RL) at different concentrations was less than unity indicating the adsorption of Cr6+ ions onto Cs/CDTA/GO is favorable. Cs/CDTA/GO adsorbent could be regenerated more than three times based on its adsorption/desorption cycles

Brine discharge of reverse osmosis (RO) desalination plants represents a challenge for both inland and coastal desalination plants. Zero-liquid discharge (ZLD) can be accomplished by using additional stages of RO, which can recycle that brine water, but the key challenge is the high concentration of divalent salts. These divalent salts (especially calcium and magnesium salts) forms a scaling layer on the RO membrane surfaces and hence shorten the life-time of the membranes. In this study, the nanofiltration (NF) procedure was used to remove divalent ions from the brine discharge to minimize the load on additional stages of RO membranes. One of the most critical considerations influencing the selection of an effective NF is the water type, which is expected here by calculation of some hydrochemical parameters (major ions, hypothetical soluble salts (electrolyte), and saturation indices). NF experiments were undertaken on a lab-scale using a low-pressure hand-made system of 4–7 bar. Synthetic single salts solutions and two real brine water discharge (brackish (BWRO) and seawater (SWRO) desalination plants) were used as a feed solution for NF system. The chemical characteristics of the RO-feed, RO-brine, NF-permeate, and NF-reject in were investigated. Electrolyte concentrations and saturation indices were determined based on the concentration of the major ions and the NETPATH software package, respectively. Calculations reveal that the brine concentrate samples contained mostly MgSO₄ and MgCl₂ soluble salts. The results show that 79–89% of the total dissolved salts (TDS) and 96–98% of the total hardness (TH) were retained using the NF process. The salt rejection of the NF membrane follows the order of CaSO₄, Na₂SO₄, MgSO₄, MgCl₂, and NaCl with a percent of 97.4, 97.3, 95.2, 93.4, and 79%, respectively.

We modified TFC membranes via a series of chemical and surface reactions. A nascent polyamide (PA) active layer was prepared by interfacial polymerization and composited with GO nanosheets then reacted with CuCl ₂ ·2H ₂ O. Finally, the composite membrane was treated with NH ₄ OH solutions.