The continuous increase in the wastes generated from forestry, timber, and paper industries has engendered the need for their transformation into economically viable materials for the benefit of mankind. This study reports the preparation and application of sawdust-derived cellulose nanocrystals (CNC) incorporated with zinc oxide as a novel adsorbent for the removal of methylene blue (MB) from water. The CNC/ZnO nanocomposite was characterized using Fourier transform infrared, X-ray diffraction (XRD), and scanning electron microscopy. The amount of MB adsorbed was determined by a UV–vis spectrophotometer. The microscopic analysis revealed that the nanocomposite had a narrow particle size range and exhibited both spherical and rod-like morphologies. The XRD analysis of the nanocomposite showed characteristic high-intensity peaks in the range of 30–75° attributed to the presence of ZnO nanoparticles, which were responsible for the enhancement of the crystallinity of the nanocomposite. The results revealed a relationship between the MB removal efficiency and changes in solution pH, nanocomposite dosage, initial concentration, temperature, and reaction time. The adsorption equilibrium isotherm, measured in the temperature range of 25–45 °C and using a concentration of 20–100 mg/L, showed that the MB sorption followed the Langmuir isotherm with a maximum adsorption capacity of 64.93 mg/g. A pseudo-second-order kinetic model gave the best fit to the experimental data. Based on adsorption performance, the CNC/ZnO nanocomposite offers prospects for further research and application in amelioration of dye-containing effluent.

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Freeze desalination is an alternative method for the treatment of mine waste waters. HybridICE(®) technology is a freeze desalination process which generates ice slurry in surface scraper heat exchangers that use R404a as the primary refrigerant. Ice separation from the slurry takes place in the HybridICE filter, a cylindrical unit with a centrally mounted filter element. Principally, the filter module achieves separation of the ice through buoyancy force in a continuous process. The HybridICE filter is a new and economical means of separating ice from the slurry and requires no washing of ice with water. The performance of the filter at a flow-rate of 25 L/min was evaluated over time and with varied evaporating temperature of the refrigerant. Behaviours of the ice fraction and residence time were also investigated. The objective was to find ways to improve the performance of the filter. Results showed that filter performance can be improved by controlling the refrigerant evaporating temperature and eliminating overflow.

In this work, cellulose nanocrystals (CNC) derived from sawdust were successfully incorporated into a nanofiltration membrane produced by the interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC). The characteristics of unmodified and CNC-modified membranes were investigated using scanning electron microscopy (SEM), Atomic Force Microscopy (AFM), zeta potential measurement, X-ray photoelectron spectroscopy (XPS), and contact angle measurement. The performance of the membranes in terms of nitrate removal and water flux was investigated using 60 mg/L of potassium nitrate solution in a dead-end test cell. The characteristics of the modified membrane revealed a more nodular structure, higher roughness, increased negative surface charge, and higher hydrophilicity than the pristine membrane, leading to nitrate rejection of 94%. In addition, the membrane gave an average water flux of 7.2 ± 1.8 L/m2/h/bar. This work implies that nanofiltration, a relatively low-pressure process compared to reverse osmosis, can be used for improved nitrate removal from drinking water using an NF membrane modified with sawdust-derived cellulose nanocrystals.

Membrane filtration of raw water obtained from Hartbeespoort dam in South Africa and spiked with four different organochlorides pesticides and three polyaromatic hydrocarbons was done using three different commercially available membranes (AFC 40, AFC80 and AFC99). The purpose was to determine important membrane characteristics for removal of organic contaminants and enhance water recovery. AFC40, a nanofiltration membrane, showed a modular structure, has 2.9% porosity and average roughness 0.76. AFC80, a reverse osmosis membrane, showed little modular structure, has 2.9% porosity and average roughness 0.79. AFC99, another reverse osmosis membrane was tight and showed no nodular structure, percentage porosity was 0.2 while average roughness was 0.67. All the membranes are hydrophilic and gave more than 99% rejection of organic solutes however water recovery was higher with AFC40 which is more hydrophilic (Contact angle 30°-40°) and lowest with AFC99 which is less hydrophilic (Contact angle 40°-63°). EDX results showed that AFC99 has the lowest sodium and sulphur contents. This may have contributed to the absence of modular structure, lower hydrophilicity, and its tightness. The FTIR analysis of the membranes indicated a significant presence of amides group (peak at 1650cm -1 ) and acyl and phenyl C-O groups in all the membranes (peak at 1150 cm -1 ). The presence of ortho disubstituted aromatic group (peak at 74 cm -1 ) was observed in both AFC40 and AFC80 but not in AFC99. This is suspected to have contributed to the tight structure of AFC99. AFC40 had little effect on the conductivity of the feed water. Membranes with higher nodular structure have a higher porosity. The presence of nodular structure increases water recovery but also allows the passage of some dissolved solids, and is therefore important in the selection of membranes for organic contaminants removal from hartbeespoort dam water.

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