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Equilibrium conditions of adsorption of a basic dye on hardwood sawdust were studied using the Langmuir and Freundlich isotherms. Two sets of experiments were carried out at different particle sizes and temperatures. The adsorption of the basic dye on hardwood was found to conform with the two isotherms. The capacity of hardwood for the adsorption of basic dye was found to increase by decreasing the particle size and increasing the temperature. The cost of hardwood adsorbent is only 8.4% that of activated carbon.

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Novel amorphous silica nanoparticle-incorporated poly(vinylidine fluoride) electrospun nanofiber mats are introduced as effective membranes for forward osmosis desalination technology. The influence of the inorganic nanoparticle content on water flux and salt rejection was investigated by preparing electrospun membranes with 0, 0.5, 1, 2, and 5 wt % SiO2 nanoparticles. A laboratory-scale forward osmosis cell was utilized to validate the performance of the introduced membranes using fresh water as a feed and different brines as draw solution (0.5, 1, 1.5, and 2 M NaCl). The results indicated that the membrane embedding 0.5 wt % displays constant salt rejection of 99.7% and water flux of 83 L m(-2) h(-1) with 2 M NaCl draw solution. Moreover, this formulation displayed the lowest structural parameter (S = 29.7 μm), which represents approximately 69% reduction compared to the pristine membrane. Moreover, this study emphasizes the capability of the electrospinning process in synthesizing effective membranes as the observed water flux and average salt rejection of the pristine poly(vinylidine fluoride) membrane was 32 L m(-2) h(-1) (at 2 M NaCl draw solution) and 99%, respectively. On the other hand, increasing the inorganic nanoparticles to 5 wt % showed negative influence on the salt rejection as the observed salt flux was 1651 mol m(-2) h(-1). Besides the aforementioned distinct performance, studies of the mechanical properties, porosity, and wettability concluded that the introduced membranes are effective for forward osmosis desalination technology.

Decolourisation of a dilute solution of a basic dyestuff was carried out by using hardwood sawdust as adsorbent. At 80°C 85% decolourisation occurred within 100 min at an initial concentration (Co) of 200 mg dm−3. There was a 44% reduction in contact time when the temperature was raised from 25 to 80°C. The rate parameter for different initial dye concentrations was found to follow the equation: kco=4.20Co0.88 and the rate parameter for different mean diameter dm followed the equation kdm=4.1 (l/dm)0.135. The activation energy of the process was 9.83 kJ mol−1 which shows that the rate controlling step is intraparticle diffusion.

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Tannery effluent is characterized not only by heavy loads but also with toxic heavy metals especially chromium ions. Chromium is considered an important source of contamination due to large volume of exhaust liquid discharged and solid sludge produced. Details on adsorption studies were carried out using synthetic chromium salts (chromium chloride) as adsorbate, and cement kiln dust (a waste from white cement industry) as adsorbent. Equilibrium isotherms have been determined for the adsorption of chromium ions on cement kiln dust. Kinetic study provided that the adsorption process is diffusion controlled. The experimental results have been fitted using Freundlich, Langmuir, and Redlich Peterson isotherms. The maximum adsorption capacity of cement kiln dust was found to be 33 mg/g. Industrial tannery effluent (22-mg/L chromium and COD 952 mg/L) was also treated by cement dust. The treated effluent (using 20 g cement dust per 1 L) contains only 0.6 mg/L chromium and COD 200 mg/L.