The use of date palm as a potential adsorbent for wastewater treatment: a review

Background

In tropical countries, the palm tree is one of the most abundant and important trees. Date palm is a principal fruit grown in many regions of the world. It is abundant, locally available and effective material that could be used as an adsorbent for the removal of different pollutants from aqueous solution.

Review

This article presents a review on the role of date palm as adsorbents in the removal of unwanted materials such as acid and basic dyes, heavy metals, and phenolic compounds. Many studies on adsorption properties of various low cost adsorbent, such as agricultural waste and activated carbons based on agricultural waste have been reported in recent years.

Conclusion

Studies have shown that date palm-based adsorbents are the most promising adsorbents for removing unwanted materials. No previous review is available where researchers can get an overview of the adsorption capacities of date palm-based adsorbent used for the adsorption of different pollutants. This review provides the recent literature demonstrating the usefulness of date palm biomass-based adsorbents in the adsorption of various pollutants.     

Review of environmental aspects and waste management of stone cutting and fabrication industries

Iran is the second largest stockholder of construction stones with 10 % of world production ;and there are more than 4000 stone cutting and fabrication industries (SCFIs). In the processing of raw stones, a considerable part of stone is turned into waste. Generated wastes include excess parts of different stones and sludge. The present paper reviews the state of SCFIs waste management using multiple data sources including site, analysis of effluent and sludge samples, and conducting interviews with people who are involved in 286 SCFIs in Qom and Tabriz. The results revealed that currently almost 35 to 52.5 % of raw stones were converted to solid wastes depending on stone cutting and processing methods, type of stones and their quality, which seemed a high percentage. Also, the effluents between 0.8 and 2.8 m³ were generated per ton of processed stone. Based on the analysis of heavy metals with atomic absorption spectroscopy, sludge samples contained a considerable amount of Pb, Cu, Cr, and Cd. It was also found that the lack of specific recycling, reuse and disposal programs and suitable supervision has led to uncontrolled disposal of stone wastes and sludge in different areas. However, there are good opportunities for reuse and recycling of the SCFIs wastes.     

Uptake of 14C-atropine and/or its transformation products from soil by wheat (Triticum aestivum var Kronjet) and their translocation to shoots

Plant uptake of toxins and their translocation to edible plant parts are important processes in the transfer of contaminants into the food chain. Atropine, a highly toxic muscarine receptor antagonist produced by Solanacea species, is found in all plant tissues and can enter the soil and hence be available for uptake by crops. The absorption of atropine and/or its transformation products from soil by wheat (Triticum aestivum var Kronjet) and its distribution to shoots was investigated by growing wheat in soil spiked with unlabeled or ¹⁴C-labeled atropine. Radioactivity attributable to ¹⁴C-atropine and its transformation products was measurable in plants sampled at 15 d after sowing (DAS) and thereafter until the end of experiment. The highest accumulation of ¹⁴C-atropine and/or its transformation products by plants was detected in leaves (between 73 and 90% of the total accumulated) with lower amounts in stems, roots, and seeds (approximately 14%, 9%, and 3%, respectively). ¹⁴C-Atropine and/or its transformation products were detected in soil leachate at 30, 60, and 90 DAS and were strongly adsorbed to soil, with 60% of the applied dose adsorbed at 30 DAS, plateauing at 70% from 60 DAS. Unlabeled atropine was detected in shoots 30 DAS at a concentration of 3.9 ± 0.1 μg kg^?1 (mean ± SD). The observed bioconcentration factor was 2.3 ± 0.04. The results suggest a potential risk of atropine toxicity to consumers.     

Effect of Habitat Complexity on Richness, Abundance and Distributional Pattern of Forest Birds

Structurally complex forests provide more diverse conditions in comparison to homogenous forests because of greater variety of microhabitats and trees. This study assesses the association of bird species richness, abundance, and distributional pattern with habitat complexity (HC) in Kheyrud Forest in the north of Iran. Birds were surveyed during spring 2009 by 100 point counts. In each point count six habitat features related to the index of HC were computed and scored from 0 to 3. Then the scores were summed and divided into two groups of low and high complexity, HC ≤ 6 and HC > 6, respectively. To compare bird richness and abundance in different HCs, a two sample t-test was used. Presence and absence of bird species at each plot as a dependent variable were compared with the vegetation characteristics as an independent variable by means of the Canonical Correspondence Analysis. The results revealed bird species richness and abundance were significantly higher in more complex habitats. Bird species can be divided into two groups, the first group including species which associated with late successional stages and the second group, species belonging to early successional stages. Numbers of birds belonging to the first group declined in less complex forests, whereas the numbers of birds belonging to the second group increased. At the stand scale, our results reveal that bird abundance and richness are strongly associated with the complexity of vegetation structure in the study area.     

Environmental monitoring of complex hydrocarbon mixtures in water and soil samples after solid phase microextraction using PVC/MWCNTs nanocomposite fiber

A novel nanocomposite based on incorporation of multiwalled carbon nanotubes (MWCNTs) in polyvinyl chloride (PVC) was prepared. Proposed nanocomposite was coated on stainless steel wire by deep coating. Composition of nanocomposite was optimized based on results of morphological studies using scanning electron microscopy. The best composition (83% MWCNTs:17% PVC) was applied as a solid phase microextraction fiber. Complex mixture of aromatic (BTEX) and aliphatic hydrocarbons (C₅–C₃₄) were selected as model analytes, and performance of proposed fiber in extraction of the studied compounds from water and soil samples was evaluated. Analytical merits of the method for water samples (LODs = 0.10–1.10 ng L⁻¹, r² = 0.9940–0.9994) and for soil samples (LODs = 0.10–0.77 ng kg⁻¹, r² = 0.9946–0.9994) showed excellent characteristics of it in ultra trace determination of petroleum type environmental pollutants. Finally, the method was used for determination of target analytes in river water, industrial effluent and soil samples.     

A mathematical model to predict the composition and generation of hospital wastes in Iran

The aim of this study is to investigate the quality and quantity of hospital wastes in Iran. The generated hospital wastes have been estimated by the number of hospitals and the number of active beds in each province of Iran in 2001. All data and information have been gathered from: (i) Iran Statistics Center, (ii) literature review, and (iii) hospital waste investigations for an average hospital. Physical analyses have been conducted in terms of various materials (plastic, textile, paper, metal, and others) and components (biological, infectious, medical, and regular wastes). Based on the above-mentioned investigation and information, a mathematical model has been developed to calculate the generation of (infectious) hospital wastes for any desired year. Utilizing the model, generated infectious hospital wastes has been estimated as 698,937 tones for 2008 (short-term) and 3,494,387 tones for 2028 (long-term period). If the real infectious wastes are collected separately, then the generated infectious wastes will be reduced by 15.1% of the above-mentioned amount (139,787 tones for 2008, and 698,877 tones for 2028). Results of physical analysis show the components of the hospital waste as: (a) infectious, 67.3%; (b) medical, 8.8%; (c) biological, 1.8%; and (d) common municipal wastes, 22.1%. An appropriate collection method requires training the staff at hospitals along with preparation of the required facilities. Of course, both of these requirements are cost intensive.     

Removal of dinitrotoluenes from water via reduction with iron and peroxidase-catalyzed oxidative polymerization: a comparison between Arthromyces ramosus peroxidase and soybean peroxidase

A two-step process for the removal of dinitrotoluene from water is presented: zero-valent iron reduction is coupled with peroxidase-catalyzed polymerization of the resulting diaminotoluenes (DAT). The effect of pH was examined in the reduction step: at pH 6 the reaction occurred much more rapidly than at pH 8. In the second step, optimal pH and substrate ratio, minimal enzyme concentration and effect of polyethylene glycol (PEG) as an additive for greater than 95% conversion of DAT, over a 3h reaction period were determined using high performance liquid chromatography. Two enzymes were investigated and compared: Arthromyces ramosus peroxidase (ARP) and soybean peroxidase (SBP). The optimal pH values were 5.4 and 5.2 for ARP and SBP, respectively, but SBP was more resistant to mild acid whereas ARP was more stable in neutral solutions. SBP was found to have a greater hydrogen peroxide demand (optimal peroxide/DAT molar ratio for SBP: 2.0 and 3.0 for 2,4-diaminotoluene (2,4-DAT) and 2,6-diaminotoluene (2,6-DAT), respectively; for ARP: 1.5 and 2.75 for 2,4-DAT and 2,6-DAT, respectively) but required significantly less enzyme (0.01 and 0.1 U ml(-1) for 2,4-DAT and 2,6-DAT, respectively) to convert the DAT than ARP (0.4 and 1.5 U ml(-1) for 2,4-DAT and 2,6-DAT, respectively). PEG was shown to have no effect upon the degree of substrate conversion for either enzyme.     

Water Quality Changes in Chini Lake, Pahang, West Malaysia

A study of the water quality changes of Chini Lake was conducted for 12 months, which began in May 2004 and ended in April 2005. Fifteen sampling stations were selected representing the open water body in the lake. A total of 14 water quality parameters were measured and Malaysian Department of Environment Water Quality Index (DOE-WQI) was calculated and classified according to the Interim National Water Quality Standard, Malaysia (INWQS). The physical and chemical variables were temperature, dissolved oxygen (DO), conductivity, pH, total dissolved solid (TDS), turbidity, chlorophyll-a, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solid (TSS), ammonia-N, nitrate, phosphate and sulphate. Results show that base on Malaysian WQI, the water in Chini Lake is classified as class II, which is suitable for recreational activities and allows body contact. With respect to the Interim National Water Quality Standard (INWQS), temperature was within the normal range, conductivity, TSS, nitrate, sulphate and TDS are categorized under class I. Parameters for DO, pH, turbidity, BOD, COD and ammonia-N are categorized under class II. Comparison with eutrophic status indicates that chlorophyll-a concentration in the lake was in mesotrophic condition. In general water quality in Chini Lake varied temporally and spatially, and the most affected water quality parameters were TSS, turbidity, chlorophyll-a, sulphate, DO, ammonia-N, pH and conductivity.     

Effect of metal tolerant plant growth promoting Bradyrhizobium sp. (vigna) on growth, symbiosis, seed yield and metal uptake by greengram plants

The nickel and zinc tolerant plant growth promoting Bradyrhizobium sp. (vigna) RM8 was isolated from nodules of greengram, grown in metal contaminated Indian soils. The plant growth promoting (PGP) potentials of strain RM8 was assessed both in the presence and absence of nickel and zinc under in vitro conditions. Strain RM8 tolerated a high level of nickel (300 microg ml(-1)) and zinc (1400 microg ml(-1)) on yeast extract mannitol agar medium. Bradyrhizobium sp. (vigna) strain RM8 produced 13.3 microg ml(-1) of indole acetic acid in Luria Bertani broth at 100 microg ml(-1) of tryptophan which increased to 13.6 microg ml(-1) at 50 microg Ni ml(-1) and 13.5 microg ml(-1) at 300 microg Zn ml(-1). Strain RM8 was positive for siderophore, HCN and ammonia both in the absence and presence of nickel and zinc. The PGP activity of this strain was further evaluated with increasing concentrations of nickel and zinc using greengram as a test crop. The bioinoculant enhanced the nodule numbers by 82%, leghaemoglobin by 120%, seed yield by 34%, grain protein by 13%, root N by 41% and shoot N by 37% at 290 mg Ni kg(-1) soil. At 4890 mg Zn kg(-1) soil, the bioinoculant increased the nodule numbers by 50%, leghaemoglobin by 100%, seed yield by 36%, grain protein by 13%, root N by 47% and shoot N by 42%. The bioinoculant strain RM8 reduced the uptake of nickel and zinc by plant organs compared to plants grown in the absence of bioinoculant. This study suggested that the bioinoculant due to its intrinsic abilities of growth promotion and attenuation of the toxic effects of nickel and zinc could be exploited for remediation of metal from nickel and zinc contaminated sites.     

A Solvent-Free Approach for Production of Films from Pectin and Fungal Biomass

Self-binding ability of the pectin molecules was used to produce pectin films using the compression molding technique, as an alternative method to the high energy-demanding and solvent-using casting technique. Moreover, incorporation of fungal biomass and its effects on the properties of the films was studied. Pectin powder plasticized with 30% glycerol was subjected to heat compression molding (120 °C, 1.33 MPa, 10 min) yielding pectin films with tensile strength and elongation at break of 15.7 MPa and 5.5%, respectively. The filamentous fungus Rhizopus oryzae was cultivated using the water-soluble nutrients obtained from citrus waste and yielded a biomass containing 31% proteins and 20% lipids. Comparatively, the same strain was cultivated in a semi-synthetic medium resulting in a biomass with higher protein (60%) and lower lipid content (10%). SEM images showed addition of biomass yielded films with less debris compared to the pectin films. Incorporation of the low protein content biomass up to 15% did not significantly reduce the mechanical strength of the pectin films. In contrast, addition of protein-rich biomass (up to 20%) enhanced the tensile strength of the films (16.1–19.3 MPa). Lastly, the fungal biomass reduced the water vapor permeability of the pectin films.